U.S. patent number RE38,183 [Application Number 08/818,224] was granted by the patent office on 2003-07-15 for synchronization circuit for visual/audio alarms.
This patent grant is currently assigned to Wheelock Inc.. Invention is credited to Edward V. Applegate, Joseph Kosich.
United States Patent |
RE38,183 |
Kosich , et al. |
July 15, 2003 |
**Please see images for:
( Certificate of Correction ) ** |
Synchronization circuit for visual/audio alarms
Abstract
A strobe alarm system which includes multiple normally
self-timed strobe circuits connected in a common loop to a fire
alarm control panel, and a sync control circuit, which may be
incorporated in the fire alarm control panel, for causing the
strobes to flash in synchronism at a predetermined rate which will
insure that a person viewing the multiple strobes would not see
flash rates higher than the predetermined synchronized rate, which
is preferably less than five flashes per second. The sync control
circuit does not interfere with the supervision functions of the
alarm system, and when an alarm condition is present it supplies
power to the strobe circuits which it then interrupts once every
flash cycle to cause a sync trigger circuit in each strobe to fire
its flashtube, and to reset the internal timer of each strobe to
ready it for arrival of the next sync signal. Each strobe circuit
in the loop includes a resettable timer for recycling its own flash
unit in a non-synchronous fail-safe mode in case the sync signal
should fail to appear within a finite period following the last
previous flash. That is, normally the strobes are all fired at the
same time in response to sync signals applied to their sync trigger
circuits, but in the event the sync signal is lacking the strobes
will continue to flash, each at a rate determined by its internal
timer.
Inventors: |
Kosich; Joseph (South Toms
River, NJ), Applegate; Edward V. (Toms River, NJ) |
Assignee: |
Wheelock Inc. (Long Branch,
NJ)
|
Family
ID: |
22458994 |
Appl.
No.: |
08/818,224 |
Filed: |
March 14, 1997 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
133519 |
Oct 7, 1993 |
05400009 |
Mar 21, 1995 |
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Current U.S.
Class: |
340/331;
315/200A; 315/241S; 340/286.05; 340/332 |
Current CPC
Class: |
G08B
5/38 (20130101); H05B 41/34 (20130101) |
Current International
Class: |
G08B
5/38 (20060101); G08B 5/22 (20060101); H05B
41/30 (20060101); H05B 41/34 (20060101); G08B
005/00 () |
Field of
Search: |
;340/331,332,333,293,286.05,286.11,326 ;365/2A,241S |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Swarthout; Brent A.
Claims
We claim:
1. A control circuit for synchronously firing at a predetermined
rate of plurality of flash units each of which has a timer trigger
circuit which normally fires the unit independently of the others,
comprising: a two-conductor power distribution line to which each
of a plurality of flash units is connected through a respective
timer trigger circuit and through a respective sync trigger circuit
connected in parallel with a corresponding timer trigger circuit; a
sync control circuit having input terminals connected across a D.C.
power source and output terminals connected to said power
distribution line, said sync control circuit comprising: first
controlled switching means connected in series between said input
terminals and said output terminals for supplying power from said
D.C. power source to said plurality of flash units .[.when and only
when an alarm condition is present.]. ; and timer means connected
across said input terminals and receiving power from said D.C.
power source when and only when an alarm condition is present, for
actuating said first controlled switching means and briefly
interrupting the supply of power to said power distribution line at
said predetermined rate for producing a sync signal for causing
said sync trigger circuits all to simultaneously fire its
respective flash unit and for re-setting the timer trigger circuit
of each flash unit to enable it to trigger the unit in the event no
sync signal arrives after elapse of a predetermined period
following the last previous sync signal.
2. A control circuit according to claim 1 .Iadd.or claim
25.Iaddend., wherein said first controlled switching means
comprises relay means having normally closed contacts connected
between said input terminals and said output terminals, and a coil
connected in series with a normally open switch across said input
terminals, wherein said switch is closed at said predetermined rate
by pulse signals generated by said timer .[.circuit.]. .Iadd.means
.Iaddend.for causing said normally closed contacts to briefly
open.
3. A control circuit according to claim 2, wherein said timer
.[.circuit.]. .Iadd.means .Iaddend.comprises a microcontroller
programmed to generate pulse signals having a duration in the range
from 10 to 30 milliseconds at intervals of about 2.9 seconds.
4. A control circuit according to claim 1, wherein each flash unit
comprises a first capacitor connected in parallel with a flash tube
across said two-conductor power distribution line, first switch
means for connecting and disconnecting an inductor across said
two-conductor power distribution line to store energy in said
inductor during periods of connection and causing energy to be
transferred from said inductor to said capacitor during periods of
disconnection of said first switch means, means including
optocoupler means connected across said power distribution line for
repetitively cycling said first switch means between open and
closed states, and wherein the timer trigger circuit includes
second switch means coupled to and operable to fire a respective
flashtube when the timer trigger circuit has timed out.
5. A control circuit according to claim 4, wherein each flash unit
further comprises means for limiting the energy coupled from said
inductor to said first capacitor to that necessary to cause firing
of said flashtube with a specified brightness at a specified
rate.
6. A control circuit according to claim 5, wherein said optocoupler
means comprises a light-emitting diode and a transistor having
base, emitter and collector electrodes, and wherein said
energy-limiting means comprises a Zener diode connected between the
base electrode of the optocoupler transistor to a terminal of said
first capacitor and poled to cause said optocoupler to stop cycling
said first switch means when the voltage on said first capacitor
has attained the threshold firing voltage of said flashtube.
7. A control circuit according to claim 4, wherein said second
switch means of each timer trigger circuit includes an SCR.
8. A control circuit according to claim 7, wherein each sync
trigger circuit includes a first resistor and a second capacitor
connected in series across a supply of D.C. voltage having an
amplitude lower than that of said D.C. power source, third switch
means and a second resistor serially connected across said second
capacitor, and means connecting the junction between said third
switch means and said second resistor to a gate electrode of the
SCR included in the respective timer trigger circuit.
9. A control circuit according to claim 7, wherein the timing
trigger circuit and the sync trigger circuit in each flash unit
share a common timing signal generator which in the absence of sync
signals generates and applies trigger pulses to the gate electrode
of said SCR at a predetermined frequency for causing said flashtube
to flash at a first rate, and which in response to application of
sync pulses generates and applies trigger pulses to the gate
electrode of said SCR at said predetermined rate.
10. A control circuit according to claim 1, wherein each flash unit
comprises a first capacitor connected in parallel with a flashtube,
means including first switch means for connecting and disconnecting
an inductor across said power distribution line to store energy in
said inductor during periods of connection and causing energy to be
transferred from said inductor to said first capacitor during
periods of disconnection of said .Iadd.first switch .Iaddend.means,
means including microcontroller means connected across said power
distribution line programmed for repetitively cycling said first
switch means between its open and closed states until said first
capacitor is charged to the threshold firing voltage of said
flashtube, wherein the timer trigger circuit and the sync trigger
circuit of each flash unit share a triggering circuit which
includes an SCR .[.connected in parallel with.]. .Iadd.electrically
coupled to .Iaddend.said flashtube, and wherein said
microcontroller means, in the absence of sync signals, generates
and applies trigger pulses to a gate electrode of said SCR at a
predetermined frequency for causing the flashtube to flash at a
first rate, and in response to the application of sync signals
generates and applies trigger pulses to the gate electrode of said
SCR at said predetermined rate.
11. A control system for synchronously firing at a predetermined
rate separate groups of flash units, each group for providing
visual alarm signals to a given zone and .[.consisting of.].
.Iadd.comprising .Iaddend.a plurality of flash units each having an
individual timing trigger circuit which normally fires
independently of one another comprising: for each zone, a
two-conductor power distribution line to which each of the
plurality of flash units included in the group is connected through
a respective timer trigger circuit, and a respective sync trigger
circuit; a sync control circuit which includes, for each zone,
first controlled switching means having input terminals connected
across a D.C. power source and output terminals connected to said
power distribution line for supplying power from said source to all
of the plurality of flash units in the zone .[.when, and only when,
an alarm condition is present in that zone.]. ; and circuit means
including a microcontroller and a power supply therefor connected
to the .Iadd.first .Iaddend.controlled switching means for all of
said zones for supplying power to said microcontroller when, and
only when, power from said D.C. source is applied to at least one
group of flash units, and wherein said microcontroller is coupled
to and is programmed to .[.ascertain to which zone or zones power
is being supplied and to.]. generate and apply to the first
controlled switching means of .[.said powered.]. .Iadd.a
.Iaddend.zone or zones a signal for actuating the same for briefly
interrupting the supply of power to the power distribution line
connected to the powered zone or zones and producing a sync signal
for causing the corresponding sync trigger circuits to fire all of
the flash units connected to the powered distribution line or
lines, and for re-setting the timer trigger circuit of all of the
flash units connected to the powered distribution line or lines for
enabling them to trigger a respective flash unit in the event no
sync signal arrives after elapse of a predetermined time period
following the last previous sync signal.
12. A control system according to claim 11 .Iadd.or claim
26.Iaddend., wherein each of said first controlled witching means
comprises relay means having normally closed contacts connected
between said input and output terminals, and a coil connected in
series with a normally open switch across a D.C. voltage source,
wherein said normally open switch is briefly closed at said
predetermined rate by pulse signals generated and applied thereto
by said microcontroller for causing brief opening of said normally
closed contacts.
13. A control system according to claim 12, wherein said
microcontroller is programmed to generate pulse signals having a
duration in the range from 10 to 30 milliseconds at intervals of
about 2.9 seconds.
14. A control .[.circuit.]. .Iadd.system .Iaddend.according to
claim 11, wherein each flash unit comprises a first capacitor
connected in parallel with a flashtube across said two-conductor
power distribution line, means including first switch means for
connecting and disconnecting an inductor across said two-conductor
power distribution line to store energy in said inductor during
periods of connection and causing energy to be transferred from
said inductor to said first capacitor during periods of
disconnection of said means, means including optocoupler means
connected across said power distribution line for repetitively
cycling said first switch means between open and closed states, and
wherein the timer trigger circuit includes second switch means
coupled to and operable to fire its respective flashtube when the
timer trigger circuit has timed out.
15. A control .[.circuit.]. .Iadd.system .Iaddend.according to
claim 14, wherein each flash unit further comprises means for
limiting the energy coupled from said inductor to said first
capacitor to that necessary to cause firing of said flashtube with
a specified brightness at a specified rate.
16. A control .[.circuit.]. .Iadd.system .Iaddend.according to
claim 15, wherein said optocoupler means comprises a light-emitting
diode and a transistor having base, emitter and collector
electrodes, and wherein said energy-limiting means comprises a
Zener diode connected between the base electrode of the optocoupler
transistor to a terminal of said first capacitor and poled to cause
said optocoupler to stop cycling said first switch means when the
voltage on said first capacitor has attained the threshold firing
voltage of said flashtube.
17. A control .[.circuit.]. .Iadd.system .Iaddend.according to
claim 14, wherein said second switch means of each timer trigger
circuit includes an SCR.
18. A control .[.circuit.]. .Iadd.system .Iaddend.according to
claim 17, wherein each sync trigger circuit includes a first
resistor and a second capacitor connected in series across a supply
of D.C. voltage having an amplitude lower than that of said D.C.
power source, third switch means and a second resistor serially
connected across said second capacitor, and means connecting the
junction between said third switch means and said second resistor
to the gate electrode of the SCR included in the respective timer
trigger circuit.
19. A control .[.circuit.]. .Iadd.system .Iaddend.according to
claim 17, wherein the timing trigger circuit and the sync trigger
circuit in each flash unit share a common timing signal generator
which in the absence of the sync signals generates and applies
trigger pulses to the gate electrode of said SCR at a predetermined
frequency for causing said flashtube to flash at a first rate, and
which in response to application of sync signals generates and
applies trigger pulses to the gate electrode of said SCR at said
predetermined rate.
20. A control .[.circuit.]. .Iadd.system .Iaddend.according to
claim 11, wherein each flash unit comprises a first capacitor
connected in parallel with a flashtube, means including first
switch means for connecting and disconnecting an inductor across a
respective power distribution line to store energy in said inductor
during periods of connection and causing energy to be transferred
from said inductor to said first capacitor during periods of
disconnection of said .Iadd.first switch .Iaddend.means, mean
including microcontroller means connected across said power
distribution line programmed for repetitively cycling said first
switch means between open and closed states until said first
capacitor is charged to the threshold firing voltage of said
flashtube, wherein the timer trigger circuit and the sync trigger
circuit of each flash unit share a flashtube triggering circuit
which includes an SCR, and wherein said microcontroller means, in
the absence of sync signals, generates and applies trigger pulses
to a gate electrode of said SCR at a predetermined frequency for
causing the flashtube to flash at a first rate, and in response to
the application of sync signals generates and applies trigger
pulses to the gate electrode of said SCR at said predetermined
rate.
21. A control system comprising two or more control systems as
defined in claim 11 .Iadd.or claim 26 .Iaddend.each for
synchronously firing at a predetermined rate respective separate
groups of flash units, wherein the microcontroller of each of said
two or more control systems includes an expansion circuit having
expansion input terminals and expansion output terminals, and
wherein the expansion output terminals of each are connected to the
expansion input terminals of another in "daisy-chain" fashion, and
wherein each expansion circuit includes means for transferring sync
signals from its expansion input terminals to its expansion output
terminals whether or not its respective microcontroller is
powered.
22. A control system according to claim 21, wherein said means for
transferring sync signals when the respective microcontroller is
not powered comprises relay means having normally closed contacts
connected between said expansion input terminals and said expansion
output terminals and a coil connected across its power supply for
said microcontroller, and wherein said means for transferring sync
signals when the respective microcontroller is powered, and
therefore energizes said relay means to open said normally closed
contacts, comprises means including optocoupler means connected
between said expansion input terminals and said microcontroller for
receiving and forwarding any sync signals appearing on said
expansion input terminals to the optocoupler means of the next
successive microcontroller.
23. A control system for firing separate groups of flash units
sequentially all within a predetermined time interval and each at a
predetermined rate, each group for providing visual alarm signals
to a given zone and .[.consisting of.]. .Iadd.comprising .Iaddend.a
plurality of flash units each having an individual timing trigger
circuit which normally fires the unit independently of the others,
comprising: for each zone, a two-conductor power distribution line
to which each of the plurality of flash units included in the group
is connected through a respective timer trigger circuit and a
respective sync trigger circuit; a sync control circuit which
includes, for each zone, first controlled switching means having
input terminals connected across a D.C. power source and output
terminals connected to said two-conductor distribution line for
supplying power from said source to all of the plurality of flash
units in that zone .[.when, and only when, an alarm condition is
present in that zone.]. ; and circuit means including a
microcontroller and a power supply therefor connected to the
.Iadd.first .Iaddend.controlled switching means for .[.all.].
.Iadd.each .Iaddend.of said zones for supplying power to said
microcontroller when, and only when, power from said D.C. source is
applied to the flash units associated with at least one zone, and
wherein said microcontroller is coupled to and is programmed to
.[.ascertain to which zone or zones power is being supplied and
to.]. generate and to sequentially apply to the first controlled
switching means of each of said zones a pulse signal for actuating
the same at staggered times within a predetermined time interval
for briefly interrupting the supply of power, if present, to the
associated power distribution line and producing a sync signal for
causing the corresponding sync trigger circuits to be fired, and
for re-setting the timer trigger circuit for all flash units
connected to a powered distribution line for enabling them to
trigger a respective flash unit in the event no sync signal arrives
after elapse of a predetermined time period following the last
previous sync signal.
24. A control system according to claim 23 .Iadd.or claim
27.Iaddend., wherein said system includes four groups of flash
units, and wherein said microcontroller is programmed to generate
four equally spaced pulse signals within an interval of about 2.9
seconds and to apply successive pulse signals each to a different
one of said four groups of flash units. .Iadd.
25. A control circuit for synchronously firing at a predetermined
rate a plurality of flash units of a fire alarm warning system,
said system including a fire alarm control panel having a power
supply for the system, comprising: a two-conductor power
distribution line to which each of said plurality of flash units is
connected through a respective sync trigger circuit; a sync control
circuit having input terminals connected to said system power
supply and output terminals connected to said power distribution
line; said sync control circuit further including (1) first
controlled switching means electrically connected between said
input terminals and said output terminals for supplying power from
said system power supply to said plurality of flash units and (2)
means connected to said input terminals and receiving power from
said system power supply when, and only when, an alarm condition is
present for actuating said first controlled switching means and
briefly interrupting the supply of power to said power distribution
line at said predetermined rate to produce sync signals at said
predetermined rate; and said sync signals being operative to
simultaneously actuate the respective sync trigger circuits of said
flash units and cause said strobe alarm units to flash at said
predetermined rate..Iaddend..Iadd.
26. A control circuit according to claim 25, wherein each flash
unit comprises a first capacitor connected in parallel with a flash
tube across said two-conductor power distribution line, first
switch means for connecting and disconnecting an inductor across
said two-conductor power distribution line to store energy in said
inductor during periods of connection and causing energy to be
transferred from said inductor to said capacitor during periods of
disconnection of said first switch means, and means including
optocoupler means connected across said power distribution line for
repetitively cycling said first switch means between open and
closed states..Iaddend..Iadd.
27. A control circuit according to claim 26, wherein each flash
unit further comprises means for limiting the energy coupled from
said inductor to said first capacitor to that necessary to cause
firing of said flashtube with a specified brightness at a specified
rate..Iaddend..Iadd.
28. A control circuit according to claim 27, wherein said
optocoupler means comprises a light-emitting diode and a transistor
having base, emitter and collector electrodes, and wherein said
energy-limiting means comprises a Zener diode connected between the
base electrode of the optocoupler transistor to a terminal of said
first capacitor and poled to cause said optocoupler to stop cycling
said first switch means when the voltage on said first capacitor
has attained the threshold firing voltage of said
flashtube..Iaddend..Iadd.
29. A control system for synchronously firing at a predetermined
rate separate groups of flash units, each group for providing
visual alarm signals to a given zone and comprising a plurality of
flash units, comprising: for each zone, a two-conductor power
distribution line to which each of the plurality of flash units
included in the group is connected through a respective sync
trigger circuit; a sync control circuit which includes, for each
zone, first controlled switching means having input terminals
connected to a power source and output terminals connected to said
power distribution line for supplying power from said source to all
of the plurality of flash units in that zone; and circuit means
including a microcontroller and a power supply therefor connected
to the first controlled switching means for each of said zones for
supplying power to said microcontroller when, and only when, power
from said source is applied to at least one group of flash units,
and wherein said microcontroller is coupled to and is programmed to
generate and apply to the first controlled switching means of one
or more of said zones a signal for actuating the same for briefly
interrupting the supply of power to the power distribution line
connected to the said one or more zones and producing a sync signal
for causing the corresponding sync trigger circuits to fire all of
the flash units connected to the powered distribution line or
lines..Iaddend..Iadd.
30. A control system according to claim 29, wherein each flash unit
comprises a first capacitor connected in parallel with a flashtube
across said two-conductor power distribution line, means including
first switch means for connecting and disconnecting an inductor
across said two-conductor power distribution line to store energy
in said inductor during periods of connection and causing energy to
be transferred from said inductor to said first capacitor during
periods of disconnection of said means, and means including
optocoupler means connected across said power distribution line for
repetitively cycling said first switch means between open and
closed states..Iaddend..Iadd.
31. A control system according to claim 30, wherein each flash unit
further comprises means for limiting the energy coupled from said
inductor to said first capacitor to that necessary to cause firing
of said flashtube with a specified brightness at a specified
rate..Iaddend..Iadd.
32. A control system according to claim 31, wherein said
optocoupler means comprises a light-emitting diode and a transistor
having base, emitter and collector electrodes, and wherein said
energy-limiting means comprises a Zener diode connected between the
base electrode of the optocoupler transistor to a terminal of said
first capacitor and poled to cause said optocoupler to stop cycling
said first switch means when the voltage on said first capacitor
has attained the threshold firing voltage of said
flashtube..Iaddend..Iadd.
33. A control system for firing separate groups of flash units
sequentially all within a predetermined time interval and each at a
predetermined rate, each group for providing visual alarm signals
to a given zone and comprising a plurality of flash units,
comprising: for each zone, a two-conductor power distribution line
to which each of the plurality of flash units included in the group
is connected through a respective sync trigger circuit; a sync
control circuit which includes for each zone, first controlled
switching means having input terminals connected to a power source
and output terminals connected to said two-conductor distribution
line for supplying power from said source to all of the plurality
of flash units in that zone; and circuit means including a
microcontroller and a power supply therefor connected to the first
controlled switching means for each of said zones for supplying
power to said microcontroller when, and only when, power from said
source is applied to the flash units associated with at least one
zone, and wherein said microcontroller is coupled to and is
programmed to generate and to sequentially apply to the first
controlled switching means of each of said zones a pulse signal for
actuating the same at staggered times within a predetermined time
interval for briefly interrupting the supply of power, if present,
to the associated power distribution line and producing a sync
signal for causing the corresponding sync trigger circuits to be
fired..Iaddend..Iadd.
34. An alarm unit for use in an alarm system, comprising: means for
connection to a two-conductor power distribution line as the sole
source of power for the alarm unit; means for producing a visual
alarm signal, the visual alarm signal producing means comprising a
first capacitor connected in parallel with a flash tube, first
switch means for connecting and disconnecting an inductor across
said two-conductor power distribution line to store energy in said
inductor during periods of connection of said first switch means
and causing energy to be transferred from said inductor to said
capacitor during periods of disconnection of said first switch
means, and means for repetitively cycling said first switch means
between open and closed states; means for detecting interruptions
of power to the alarm unit over said power distribution line; and
means for triggering the visual alarm signal producing means in
response to the detection of a first interruption of power of a
first predetermined duration of time..Iaddend..Iadd.
35. The alarm unit of claim 34, wherein each flash unit further
comprises means for limiting the energy coupled from said inductor
to said first capacitor to that necessary to cause firing of said
flashtube with a specified brightness at a specified
rate..Iaddend..Iadd.
36. The alarm unit of claim 35, wherein: said repetitively cycling
means includes optocoupler means comprising a light-emitting diode
and a transistor having base, emitter and collector electrodes; and
said energy-limiting means comprises a Zener diode connected
between the base electrode of the optocoupler transistor to a
terminal of said first capacitor and poled to cause said
optocoupler to stop cycling said first switch means when the
voltage on said first capacitor has attained the threshold firing
voltage of said flashtube..Iaddend..Iadd.
37. An alarm unit for use in an alarm system, comprising: means for
producing a visual alarm signal; means for connection to a
two-conductor power distribution line as the sole source of power
for the alarm unit; means for detecting interruptions of power to
the alarm unit over said power distribution line; means for
triggering the visual alarm signal producing means in response to
the detection of a first interruption of power of a first
predetermined duration of time; and timer means for triggering the
visual alarm signal producing means in the event no power
interruption is detected within a predetermined time interval
following the detection of a prior power
interruption..Iaddend..Iadd.
38. The alarm unit of claim 37, wherein the timer triggering means
includes switch means coupled to and operable to fire said
flashtube upon the expiration of said predetermined time
interval..Iaddend..Iadd.
39. The alarm unit of claim 38, wherein: the switch means of the
timer trigger means includes and SCR; and the timer means for
triggering the visual alarm signal producing means includes a first
resistor and a capacitor connected in series across a voltage
supply having an amplitude lower than that of the power supplied to
the alarm unit, second switch means and a second resistor serially
connected across said capacitor, and means connecting the junction
between said second switch means and said second resistor to a gate
electrode of said SCR..Iaddend..Iadd.
40. The alarm unit of claim 37, wherein: the visual alarm signal
producing means comprises a first capacitor connected in parallel
with a flashtube, means including first switch means for connecting
and disconnecting an inductor across said power distribution line
to store energy in said inductor during periods of connection of
the first switch means and causing energy to be transferred from
said inductor to said first capacitor during periods of
disconnection of said first switch means, and means including
microcontroller means programmed for repetitively cycling said
first switch means between its open and closed states until said
first capacitor is charged to the threshold firing voltage of said
flashtube; the timer trigger means and the means for triggering the
visual alarm signal producing means in the absence of a power
interruption share a triggering circuit which includes an SCR
electrically coupled to said flashtube; and the microcontroller
means, in the absence of said power interruptions, generates and
applies trigger pulses to a gate electrode of said SCR at a
predetermined frequency for causing the flashtube to flash at a
first rate and, in response to the detection of power
interruptions, generates and applies trigger pulses to the gate
electrode of said SCR..Iaddend..Iadd.
41. An alarm unit for use in an alarm system, comprising: means
connectable to a two-conductor power distribution line for
receiving power as the sole source of power for said alarm unit;
means for generating a visual alarm signal; means for detecting
predetermined-pattern variations in said power signal and, in
response thereto, for controlling the operation of said visual
alarm generating means; and means for causing said visual alarm
signal generating means to generate a visual alarm signal in the
event a first predetermined-pattern variation in said power is not
again detected within a predetermined time period following the
preceding detection of said first predetermined-pattern variation
in said power signal..Iaddend..Iadd.
42. A sync control circuit for use in an alarm system having (1) a
fire alarm control panel with a power source, (2) a plurality of
alarm units, and (3) a two-conductor power distribution line as the
sole source of power for said plurality of alarm units, each of
said alarm units comprising means for producing a visual alarm
signal and means for triggering said visual alarm signal producing
means in synchronization with all other alarm units upon receiving
a sync pulse, the sync control circuit comprising: a set of input
terminals and a set of output terminals, the set of input terminals
receiving power from said power source which is to be supplied to
the alarm units over said two-conductor line; a switching means
connected between said set of input terminals and said set of
output terminals; and control means for actuating the switching
means to interrupt power to the alarm units at a predetermined rate
for producing a sync pulse to cause each alarm unit to produce a
visual alarm signal simultaneously with the other alarm units in
the system..Iaddend..Iadd.
43. The sync control circuit of claim 42, further comprising timer
means connected across said set of input terminals, and receiving
power from said power source when, and only when, an alarm
condition is present, for actuating said switching means and
briefly interrupting the supply of power to said power distribution
line at a predetermined rate for producing sync signals for causing
the visual alarm signal producing means of the alarm units all to
simultaneously generate visual alarm signals..Iaddend..Iadd.
44. The sync control circuit of claim 43, wherein said switching
means comprises relay means having normally closed contacts
connected between said set of input terminals and said set of
output terminals, and a coil connected in series with a normally
open switch across said set of input terminals, wherein said switch
is closed at said predetermined rate by pulse signals generated by
said timer means for causing said normally closed contacts to
briefly open..Iaddend..Iadd.
45. The sync control circuit of claim 44, wherein said timer
circuit comprises a microcontroller programmed to generate pulse
signals having a duration in the range of from 10 to 30
milliseconds at said predetermined rate..Iaddend..Iadd.
46. A control system according to any one of claims 11, 23, 29 and
33 wherein said microcontroller is further coupled to and
programmed to ascertain to which zone or zones power is being
supplied..Iaddend..Iadd.
47. A system comprising two or more control system as defined in
any one of claims 11, 23, 29 and 33, wherein the respective sync
control circuits of said two or more control systems include
expansion circuits that are electrically interconnected such that
signals generated by any one of said microcontrollers for actuating
the first switching means of a zone or zones controlled by said one
microcontroller are electrically coupled to the other one or more
microcontrollers for control of the first switching means of a zone
or zones controlled by said other one or more
microcontrollers..Iaddend.
Description
BACKGROUND OF THE INVENTION
This invention relates to circuits for electronic strobe lights
such as are used to provide visual warning in electronic fire alarm
devices and other emergency warning devices and, more particularly,
to a control circuit for causing plural strobes connected to the
same fire alarm control panel to flash on synchronism with one
another.
Strobe lights are used to provide visual warning of potential
hazards or to draw attention to an event or activity. An important
field of use for strobe lights is in electronic fire alarm systems,
frequently in association with audible warning devices, such as
horns, to provide an additional means for alerting persons who may
be in danger. Strobe alarm circuits include a flashtube and a
trigger circuit for initiating firing of the flashtube, with the
energy for the flash typically supplied from a capacitor connected
in shunt with the flashtube. In some known systems, the flash
occurs when the voltage across the flash unit (i.e., the flashtube
and associated trigger circuit) exceeds the threshold value
required to actuate the trigger circuit, and in others the flash is
triggered by a timing circuit. After the flashtube is triggered it
becomes conductive and rapidly discharges the stored energy from
the shut capacitor until the voltage across the flashtube has
decreased to a value at which the flashtube is extinguished and
becomes non-conductive.
In a typical installation, a loop of several flash units is
connected to a fire alarm control panel which includes a power
supply for supplying power to all flash units in the loop when an
alarm condition is present. The supply voltage may typically be 12
volts or 20-31 volts, and may be either D.C. supplied by a battery
or a full-wave rectified voltage. Underwriters Laboratories
specifications require that operation of the device must continue
when the supply voltage drops to as much as 80% of nominal value
and also when it rises to 110% of nominal value. The power supply
typically is provided from first and second terminals which will
normally have negative and positive polarity, respectively, when no
alarm condition is present, and which reverse when an alarm
condition is present, as is usual in supervised systems. When an
alarm condition is present, power is supplied to all of the strobe
units connected in the loop, with each unit firing independently of
the others at a rate determined by its respective charging and
triggering circuits and satisfying UL specifications that the flash
rate of such visual signalling devices must fall between 20 and 120
flashes per minute.
To counteract claims by epileptic groups that viewing multiple
visual signalling devices each flashing at different points in time
may trigger a seizure in susceptible individuals. Underwriters
Laboratories may additionally require that such signalling systems
be controlled in a manner to insure that an individual viewing
multiple units could see effective flash rates no higher than 5
flashes per second. Thus, there is a need for controlling multiple
self-timed visual signalling devices in a way which will insure
that individuals viewing multiple units could see effective flash
rates no higher than 5 flashes per second.
It is a primary object of the present invention to provide a
circuit having these properties and which also will work with: (a)
both D.C. and full-wave power rectified supplies; (b) all fire
alarm control panels; (c) mixed strobes (i.e., 110 candela and 15
candela); and (d) audio as well as visual signalling devices.
Another object of the invention is to provide a circuit having
these properties which can be manufactured at relatively low
cost.
Another object is to provide a control circuit which will not
interfere with the supervision function of the alarm system, and
which will be compatible with both constant power and constant
current strobe circuits.
Still another object is to provide a control circuit for
synchronizing flashing of multiple strobes which, in the event of
its failure, will allow each of the individual strobes to flash at
its own self-timed rate.
Another object of the invention is to provide such control circuit
for synchronizing flashing of multiple strobes and having
capability to limit the energy per flash of the associated strobe
circuits to that required to meet mandated requirements.
SUMMARY OF THE INVENTION
In accordance with the invention, a control circuit is provided
which causes multiple strobes connected in a common circuit or loop
to flash at the same time, in synchronism, at a rate no higher than
a predetermined rate, for example, 5 flashes per second. The
control circuit, which may either be incorporated in the fire alarm
control panel which controls the loop, or interposed between the
fire alarm control panel and the loop of strobes, derives its power
from the control panel in the same way as the strobes do: during
supervision when the polarity of the power supply is reversed, it
uses no power, but when an alarm condition is present it becomes
powered and starts operating in a sync: node. When in the sync
mode, once every flash cycle, typically at intervals of 2.9
seconds, the control circuit interrupts power to all of the strobes
for a period of from 10 to 30 milliseconds, this being the signal
which causes all of the strobes in the loop to flash. At the same
time, this signal resets the internal timer of each flash unit to
ready it for arrival of the next sync signal. In the event no sync
signal arrives after an interval exceeding 2.9 seconds, each strobe
unit will flash when its flash timer completes its cycle.
The synchronizing control circuit of the invention may be used in
conjunction with a variety of strobe circuit designs, preferably
having the following desirable properties: (a) an energy limiter
operable over a predetermined voltage range in the sync mode; (b) a
trigger circuit which is responsive to the sync signals; and (c) a
resettable timer for recycling the strobe unit in a non-sync mode
in case of lack of the sync signal.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects, features, and advantages of the invention will
become apparent, and its construction and operation better
understood, from reading the following detailed description with
reference to the accompanying drawings, in which:
FIG. 1 is a block diagram of a synchronized strobe system according
to the invention;
FIG. 2 is a circuit diagram, partially schematic and partially
block, of a strobe circuit useful in describing the features of a
strobe circuit essential to being fired synchronously with
others;
FIG. 3 is a circuit diagram of a strobe synchronizing controller
according to the invention;
FIG. 4 is a flow chart of the functions of the strobe synchronizing
controller of FIG. 3;
FIG. 5 is a circuit diagram of a first embodiment an optocoupler
strobe useful in the system of FIG. 1;
FIG. 6 is a diagram which illustrates a modification of the circuit
of FIG. 5;
FIG. 7 is a circuit diagram of a third embodiment of an optocoupler
strobe circuit wherein flashing of the strobe is controlled by a
timer;
FIG. 8 is a circuit diagram of a microprocessor-controlled strobe
useful in the system of FIG. 1;
FIGS. 9 and 10, when placed together as shown in FIG. 11, is a
circuit diagram of a 4-channel strobe synchronizing controller
according to the invention;
FIG. 11 is a diagram showing the arrangement of FIGS. 9 and 10;
FIG. 12 is a flow chart of the functions of the strobe
synchronizing controller of FIGS. 9 and 10;
FIG. 13 is a simplified block diagram showing the interconnection
of a plurality of a 4-channel controllers of the kind illustrated
in FIGS. 9 and 10; and
FIG. 14 is a simplified flow chart of alternative functions of the
strobe synchronizing controller of FIGS. 9 and 10.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1, multiple strobe circuits 10, 12 and 14
numbered from 1 to N, connected in a common loop and having the
usual end of line resistor 16, are all caused to flash at the same
time, in synchronism, by a sync control circuit 18. The sync
control module 18 may either be incorporated in a conventional fire
alarm control panel 20, as indicated by the doted line enclosure
22, or may be a free-standing unit interposed between the control
panel and the first strobe circuit 10 of the loop. Sync control
module 18 is energized from a D.C. power source embodied in control
panel 20 in the same way that loop-connected strobes are usually
energized in a supervised alarm system. During supervision, when
the polarity of the power supply is reversed from that indicated in
FIG. 1, module 18 uses no power (nor does it supply power to the
strobes), but when an alarm condition is present the polarity of
the voltage is as shown, which causes the control module to
commence operation in a sync mode, which includes supplying D.C.
power to the multiple strobes via a two-wire loop. The sync control
module causes all of the strobes in the loop to cyclically flash in
synchronism by periodically interrupting the supply of power to the
strobes. Typically, the power is interrupted for a period of from
10 to 30 milliseconds, at intervals of 2.9 seconds, so as to cause
all strobes to flash once about every 3 seconds. This flash rate
satisfies the UL requirement of a minimum of one flash every three
seconds and a maximum of three per second. This synchronizing
signal, namely, the brief interruption in the supply voltage, in
addition to triggering firing of the multiple strobes also resets
the internal timer of each strobe unit to ready it for arrival of
the next sync signal, and to enable it to self-fire in the event no
synchronizing signal arrives after an interval exceeding 2.9
seconds following the last previous flash.
As will later be explained in detail, sync control circuit 18 is
designed to synchronize flashing of multiple loop-connected strobes
of various designs including, for example, modifications of the
optocoupler strobe circuit described in U.S. Pat. No. 5,121,033
granted on Jun. 9, 1992 to applicant Kosich, and of the
microprocessor-controlled strobe disclosed in applicants' U.S.
patent application Ser. No. 08/061,965 filed May 14, 1993, and
assigned to the same assignee as the present application. In order
for the present sync circuit to work with a particular one of these
strobe circuits, the strobe must be modified to include as a
minimum the features and properties embodied in the basic strobe
circuit depicted in FIG. 2, several of which may be connected in
the loop of the system shown in FIG. 1. The flash unit 10 includes
a flashtube DS1 shunted by a trigger circuit which includes a
resistor R1 connected in series with the combination of a timer
trigger 32 connected in parallel with the series combination of a
capacitor C1 and the primary winding of an autotransformer T1. The
secondary winding of the autotransformer is connected to the
trigger band of the flashtube and when timer trigger 32 is fired
capacitor C1 discharges through the autotransformer and produces a
high voltage trigger pulse which, if the voltage across the
flashtube, as determined by a capacitor C2 connected in parallel
with the flashtube, exceeds its threshold firing voltage, causes
the flashtube to conduct and quickly discharge capacitor C2.
Capacitor C2 is incrementally charged from a suitable D.C.-to-D.C.
oscillator 34 through an inductor L1 which is connected to the
positive terminal of capacitor C2 through a resistor R2 connected
in series with a diode D2. The node between inductor L1 and
resistor R2 is connected to ground through a switch Q1, which may
be a MOSFET. The D.C.-to-D.C. oscillator 34 is connected across a
D.C. voltage source, represented by V.sub.in, and includes means
for closing and opening switch Q1 for connecting and disconnecting
inductor L1 across the D.C. source. Energy is stored in the
inductor during closed periods of the switch and this stored energy
is transferred from the inductor to capacitor C2 during open
periods of the switch. The repetitive opening and closing of switch
Q1, which may cycle at a frequency in the range from about 3,000 Hz
to about 30,000 Hz, will eventually charge capacitor C2 to the
firing threshold voltage of the flashtube.
Faced with the reality that the supply voltage to strobe alarms,
even through typically D.C., may vary between wide limits, in order
to meet UL specifications that the flash rate of the strobe must
meet minimum requirements for the range of voltages for which the
strobe is to operate, strobe circuits have heretofore been designed
to expend the required energy for the lowest reasonably expected
voltage. As a consequence, supply voltages greater than the lowest
reasonably expected value would unnecessarily expend energy in the
flash above the minimum, more often than needed and/or in a
non-useful manner. For example, the capacitor C2 connected across
the flashtube charges faster for higher input voltages; thus, if
the flash is actuated when the potential across the capacitor
attains the threshold firing voltage of the flashtube, the flash
rate will increase, resulting not only in a waste of energy but
also unnecessary wear and tear on the capacitor. In the case of the
flashtube being triggered by a separate timing circuit, such as the
timer trigger 32, a higher input voltage will cause overcharging of
the storage capacitor, or at least make it necessary to provide a
larger capacitor than should be necessary. As a result, the
potential across the capacitor will cause a brighter than necessary
flash, thereby wasting energy.
In order to minimize unnecessary expenditure of energy, yet provide
sufficient energy per flash at a constant frequency to meet minimum
standards, the strobe circuit of FIG. 2 includes an energy limiter
circuit which adjusts the amount of energy transferred to capacitor
C2 responsively to changes in amplitude of the supply voltage. The
energy limiter may take the form of a voltage regulator 36
connected in series with D.C.-to-D.C. oscillator 34 across the
voltage source. Alternatively, it may be a voltage regulator 36'
connected between oscillator 34 and the positive terminal of
capacitor C3, or a voltage regulator 36" connected from the
junction of inductor L1 and resistor R2 to the negative side of the
voltage source.
In order that the strobe circuit of FIG. 2 be triggered by sync
control module 18, a positive potential is normally supplied to a
sync trigger circuit 38 via a conductor 40 connected to the
positive terminal of the voltage source (which, it will be seen is
a positive output terminal of sync control module 18). This
potential also normally powers the internal timer trigger 32. Each
time sync control module 18 briefly interrupts this voltage, timer
trigger 34 is disabled and sync trigger 38 is enabled and triggers
the firing of the flash unit.
The preferred embodiment of the sync control circuit 18 shown in
FIG. 3 is connected across a D.C. voltage source which supplies a
voltage V.sub.in. The supply voltage V.sub.in may have a wide range
of values, from 20 volts to 31 volts, for example, in a nominally
24 volt system. The voltage is normally applied through a double
pole double throw relay K1, shown in its normal position, to a pair
of output terminals which supply a voltage V.sub.out to the input
terminals of strobe units 10, 12, . . . . . . . N connected in the
loop. That is to say, except when it is operating in a sync mode,
the sync control circuit simply provides a direct connection from a
D.C. voltage source, typically housed in the fire alarm control
panel 20, to the loop connected strobes, so as to enable each of
them to operate independently of the others at a flash rate
determined by its internal timer.
The supply voltage V.sub.in is also applied through a diode D1,
which typically has a voltage drop of 0.7 volt, to a regulator
circuit which includes resistors R4, R5, R6 and R7, a transistor
switch Q1 and an integrated circuit U1 connected as shown and
having component values so as to provide a regulated 5.00.+-.1%
volt supply to the V.sub.cc input of a microcontroller U2. One
terminal of resistor R4 is connected to the cathode of diode D1 and
at the other terminal is connected to both resistor R5 and the
collector of a switch Q1, which in this case is a transistor. The
other terminal of resistor R5 is connected to the base electrode of
switch Q1 and to an integrated circuit U1, which acts as a
controlled Zener for providing a precise 5.00 volts supply.
Resistor R7 is connected between the emitter of switch Q1 and the
control pin of integrated circuit U1. Resistor R6 is connected at
one end to both resistor R6 and the control pin of integrated
circuit U1 and at the other end to one end of U1, which is
connected to the negative side of the voltage source. Resistors R6
and R7 are of equal value for biasing integrated circuit U1. A
reset circuit for microcontroller U2 includes a diode D3, a
resistor R1 and a capacitor C3. Diode D3 and resistor R1 are
connected to each other in parallel, the cathode of diode D3 being
connected to the emitter of switch Q1 and its anode being connected
to both the positive terminal of a capacitor C3 and the "CLEAR"
input to microcontroller U2. The other terminal of capacitor C3 is
connected to the negative side of the voltage source.
As noted earlier, a regulated potential of 5.00 volts is applied at
V.sub.cc of microcontroller U2; its V.sub.ss terminal is connected
to the negative side of the voltage source. A capacitor C4
connected across V.sub.cc and V.sub.ss acts as a filter. A
resonator circuit 94 consisting of an oscillator Y1 and capacitors
C1 and C2 is connected across the two oscillator inputs of, and
supplies 4 MHz oscillations to, microcontroller U2. Capacitors C1
and C2 are respectively connected between the first and second
oscillator inputs of the microcontroller and the negative side of
the voltage source.
Before describing the function of the microcontroller U2, the
components of the circuit affected thereby will be described.
Connected across V.sub.in is a branch consisting of a diode D2,
having a voltage drop of approximately 0.7 volt, a switch Q3, in
this embodiment a Darlington transistor pair, the coil of relay K1
and a switch Q2, which in this embodiment is a MOSFET. The voltage
applied to the base electrode of one transistor of the Darlington
pair is regulated by a resistor R8 and a Zener diode D4
series-connected in that order between the cathode of diode D2 and
the end of the coil of relay K1 that is connected to switch Q2.
Switch Q2 is cycled between a conducting state and a nonconducting
state by an output of microcontroller U2 which is applied to the
gate of switch Q2 via a voltage divider including a resistor R2
connected from the output (Pin 9) of microcontroller U2 to the
gate, and a resistor R3 connected from the gate electrode to the
negative side of the power source. When switch Q2 is closed, the
potential at the output emitter of switch Q3 is pulled to that of
the negative side of the source, causing switch Q3 to conduct and
thereby cause current to flow through the coil of relay K1 and
switch the relay from its normal position to the other set of
contacts. Actuation of the relay reverses the polarity of
V.sub.out, which amounts to interrupting the positive D.C. voltage
normally supplied to the controlled strobe units. When switch Q2 is
opened, switch Q3 stops conducting, the relay is deenergized and
V.sub.out is returned to its original polarity. By controlling the
opening and closing of switch Q2, the rate at which the voltage
supplied to the strobes is interrupted, and for how long, is
regulated.
The real time clock and prescaler of microcontroller U2, which in
this embodiment is a PIC16C71 microcontroller having 8-bit
resolution, are used to produce signals for accurately controlling
the ON time of switch Q2. Typically, the real time clock and
prescaler routine produce pulses at Pin 9 which cause switch Q2 to
be ON, and therefore interrupt power to the strobes, for a period
of from 10 to 30 milliseconds, and to be OFF or open for 2.9
seconds. As illustrated by the simplified flow chart of FIG. 4,
upon initialization by the main microcontroller program, switch Q2
is open and relay K1 is in the condition shown in FIG. 3. Following
a delay of 2.9 seconds, the desired flash cycle of the controlled
strobes, switch Q2 is closed and switch Q3 conducts and energizes
relay K1 for a period of 10 to 30 milliseconds, following which the
relay is again turned off and the process is repeated. If for any
reason microcontroller U2 should fail to deliver a pulse to switch
Q2 2.9 seconds later, the relay will remain OFF and D.C. power will
be supplied to the individual controlled strobes, allowing each to
operate independently under control of its internal timing
trigger.
By way of example, the circuit shown in FIG. 3, when energized from
a 24 volt DC power source, may use the following parameters to
obtain the desired switching cycle:
ELEMENT VALUE OR NO. C1, C2 CAP., 33 pF, 200 V C3 CAP., 47 .mu.F C4
CAP., 15 .mu.F, 16 V D1, D2 DIODE, 1N4007 D3 DIODE, 1N914 D4 DIODE,
1N4742A Q1 TRANSISTOR, 2N5550 Q2 TRANSISTOR, IRF710 Q3 TRANSISTOR
TIP122 R1 RES., 39 K, 1 W, 5% R2 RES., 220, 1 W, 5% R3 RES., 100 K,
1 W, 5% R4 RES., 330, 1 W, 5% R5 RES., 4.7 K, 1 W, 5% R6, R7 RES.,
10 K, 1 W, 1% R8 RES., 4.7, 1 W, 5% 4.7 K U1 LC., TL431A K1 RELAY,
DPDT U2 LC., PIC16C34 Y1 CERAMIC RES., 4 MHZ
As discussed earlier, sync control circuit 18 (FIG. 3) is designed
to synchronize flashing of strobes of various designs, including an
optocoupler strobe circuit of the type described in U.S. Pat. No.
5,121,033, provided it has the features depicted in FIG. 2. A
currently preferred modification of the patented optocoupler
strobe, shown in FIG. 5, differs from the patented circuit in the
respects that it includes means for limiting the energy expended; a
sync trigger circuit; and, a re-settable internal trigger to enable
it to self-fire in the event the sync control circuit fails to
deliver a sync pulse at the appropriate time. A storage capacitor
C1 connected in parallel with the flashtube is incrementally
charged from an inductor L1 which is connected to the positive
terminal of the capacitor through a resistor R3 connected in series
with a diode D2. The rate at which increments of energy are
transferred from inductor L1 to capacitor C1 is determined by an
optocoupler circuit which includes a resistor R2 connected in
series with inductor L1. When a switch Q1 is closed and connects
the inductor across the D.C. voltage source, V.sub.in, the voltage
developed across resistor R2 is indicative of the magnitude of the
current flowing through inductor L1. Opening of switch Q1 is
controlled by an optocoupler U1 consisting of a light-emitting
diode optically coupled to a phototransistor detector. The voltage
at the collector electrode of the transistor portion of the
optocoupler, and at the base electrode of switch Q1, is established
by a voltage divider consisting of a resistor R8 and a Zener diode
Z2 connected in series across the D.C. supply, a capacitor C4
connected in parallel with diode Z2 and a resistor R1 connected
from the junction of resistor R8 and diode Z2 to the aforesaid
transistor collector electrode and to the base electrode of switch
Q1. The diode Z2 protects switch Q1 against over-voltage and
provides the regulated voltage required for the timing circuit. The
capacitor C4 filters the regulated voltage, and is particularly
needed when the D.C. source is a full-wave rectified supply.
As power is initially supplied to the circuit (that is, during the
2.9 seconds periods between sync signals from the sync control
circuit) the LED and transistor of optocoupler U1 are both "off"
and switch Q1 quickly turns "on" and connects inductor L1 across
the D.C. source. Closing of switch Q1 initiates charging of the
inductor L1 and a buildup of current through an isolating diode D1
and resistor R2. When the current flowing through inductor L1
attains a value sufficient to develop a voltage across resistor R2
of approximately 1.2 volts, the conduction threshold voltage of the
LED portion of the optocoupler, the diode is turned "on" and
illuminates the transistor portion to turn it "on" which, in turn,
causes switch Q1 to be turned "off" thereby to disconnect inductor
L1 from across the D.C. source. During the open "off" period of
switch Q1, energy stored in inductor L1 is transferred through
resistor R3 and diode D2 to capacitor C1. Upon cessation of current
flow through resistor R2 due to opening of switch Q1, the voltage
drop across resistor R2 is no longer sufficient to keep the LED
"on", the transistor stops conducting, switch Q1 is again turned
"on" and the cycle is repeated.
The "on" and "off" periods of switch Q1 are determined by the
switching characteristics of optocoupler U1, the values of
resistors R1, R2, R8 and Zener diode Z2, the values of inductor L1
and the voltage of the D.C. source, and may be designed to cycle at
a frequency in the range from about 3000 Hz to about 30,000 Hz. The
repetitive opening and closing of switch Q1 eventually charges
capacitor C1 to the point at which the voltage across it attains a
threshold value required to fire the flashtube. Overcharging of
capacitor C1 by a higher than designed source voltage is prevented
by a resistor R5 and a Zener diode Z1 connected in series between
the base electrode of the optocoupler transistor and the positive
electrode of storage capacitor 12. The values of these components
are chosen so that when the voltage across capacitor C1 attains the
firing threshold voltage of the flashtube, a positive potential is
applied to the base electrode of the optocoupler transistor and
turns "on" the transistor which, in turn, turns switch Q1 "off" and
disconnects inductor L1 from across the D.C. source.
The timer trigger circuit of the flash unit includes a resistor R4
connected in series with the combination of a switch Q3, which is
this embodiment is an SCR, connected in parallel with the series
combination of a capacitor C2 and the primary winding of an
autotransformer T1, the secondary winding of which is connected to
the trigger band of the flashtube. When the voltage across the
flashtube exceeds its threshold firing voltage, switch Q3 conducts
and the charge on capacitor C2 flows through the primary of
transformer T1, inducing a high voltage pulse in its secondary and
causing the flashtube to conduct. As previously mentioned, the
flashtube quickly discharges the energy stored in capacitor C1,
readying it to be recharged from the inductor L1 through diode
D2.
The strobe circuit of FIG. 5 is triggered by the sync control
module 18, to the exclusion of the just-described timer trigger, by
a sync trigger circuit which includes a resistor R7 and a capacitor
C3 connected in series in that order between the junction of
resistor R8 and diode Z2 and the negative side of the power source.
A switch Q2, which in this embodiment is a programmable unijunction
transistor, is connected in series with a resistor R6 across
capacitor C3, and a voltage divider consisting of series-connected
resistors R9 and R10 is connected in parallel with the series
combination of resistor R7 and capacitor C3. The junction of
resistors R9 and R10 is connected to the gate electrode of the PUT,
and the positive terminal of resistor R6 is connected to the gate
electrode of the SCR Q3.
When the regulated voltage supplied to the sync trigger circuit is
interrupted by operation of sync control module 18, the previously
charged capacitor C3 discharges through resistor R7, and when the
voltage on capacitor C3 reaches a predetermined level as determined
by the characteristics of switch Q2 and the resistance values of
resistors R9 and R10, switch Q2 is turned "on" which, in turn,
turns SCR Q3 "on" to fire the flashtube. Shortly after the
flashtube fires, the short interruption period of the applied
potential terminates, and a positive potential is again applied to
diode D1 thereby to ready the circuit for arrival of the next sync
pulse. In this embodiment, resistors R9 and R10 are external to
switch Q2, enabling better tolerance control over their values than
when these resistors are internal to switch Q2 as is the case in
the modified circuit shown in FIG. 6, which in all other respects
is identical to the circuit of FIG. 5. In the FIG. 6 switch Q2 is
not a PUT but, instead, is a unijunction transistor having two
internal resistors corresponding to resistors R9 and R10. Thus, the
modification shown in FIG. 6 has two fewer parts then the FIG. 5
circuit, at the possible expense of less tolerance control.
By way of example, the circuit illustrated in FIG. 5, and the
modification thereof shown in FIG. 6, when energized from a 24 volt
D.C. power source, may use the following parameters for the circuit
elements:
ELEMENTS VALUE OR NO. C1 CAP., 47 .mu.F, 250 V C2 CAP., .047 .mu.F,
400 V C3 CAP., 15 .mu.F, 5% C4 CAP., 15 .mu.F, 5% D1 DIODE, 1N4007
D2 DIODE, HER106 L1 INDUCTOR, 8.5 mH Z1 DIODE, 240 V. Z2 DIODE, 9.1
V., 5% Q1 TRANSISTOR, IRF710 Q2 PUT 2N6027 (FIG. 5); UJT 2N2646
(FIG. 6) T1 TRIGGER TRANSFORMER DS1 FLASHTUBE Q3 SCR, EC103D R1
RES., 22 K, 1 W R2 RES., 16.9 R3 RES., 180, 1 W R4 RES., 220 K R5
RES., 33 K R6 RES., 47 R7 RES., 220 K R8 RES., 4.7 K R9, R10 RES.,
10 K, 1% U1 OPTOCOUPLER, 4N37
FIG. 7 is a circuit diagram of another strobe circuit utilizing an
optocoupler for D.C.-to-D.C. conversion in which a combination of a
CMOS timer and an SCR is used to control firing and triggering of
the flashtube in both the synchronous and non-synchronous modes of
operation. Briefly, a capacitor C6 connected in parallel with the
flashtube is incrementally charged through a diode D5 and a
resistor R11 from an inductor L1, which is cyclically connected and
disconnected across a D.C. supply by a switch Q3 controlled by an
optocoupler U2. A Zener diode D2 and a resistor R9 series-connected
between the base electrode of the transistor of the optocoupler and
the positive terminal of capacitor C6 shuts off the D.C./D.C.
oscillator when the capacitor is charged to maximum capacity,
thereby limiting the energy supplied to the flashtube to only what
is necessary. The trigger circuit for the flashtube includes a
resistor R10 connected in series with the combination of a switch
Q2, which in this embodiment is an SCR, connected in parallel with
the series combination of a capacitor C1 and the primary winding of
an autotransformer T1, the secondary of which is connected to the
trigger band of the flashtube. When switch Q2 is turned "on" in a
manner to be described presently, capacitor C1 discharges through
the primary of transformer T1 and induces a high voltage in the
secondary winding which, if the voltage on capacitor C6 equals the
threshold firing voltage of the tube, causes the flashtube to
conduct and quickly discharge capacitor C6.
In this embodiment, switch Q2 is turned "on" in both the
synchronous and self-timed modes of operation by an integrated
circuit timer U1 which, in this embodiment is a KS555 timer. The
KS555 is a stable timer capable of producing accurate time delays
or frequencies, which for stable operation as an oscillator, as
here used, the free-running frequency and the duty cycle are both
accurately controlled by two resistors R3 and R2 and a capacitor C3
connected in series in that order between the junction of a
resistor R6 connected in series with a Zener diode D3 and the
negative side of the D.C. supply. The Zener D3 regulates the
voltage applied to the V.sub.cc terminal of the timer and to the
junction between resistors R6 and R3. The "THRES" and "TRIG"
terminals of the timer are connected to the junction between
resistor R2 and capacitor C3 and the DISCHARGE terminal is
connected to the junction of resistors R3 and R2. The RESET
terminal is connected to the junction between a resistor R7 and a
capacitor C5 connected in series across the D.C. supply, and the
OUTPUT terminal is connected to the base electrode of a switch Q1,
which in this embodiment is a transistor. The junction between
resistor R7 and capacitor C5 is also connected via a diode D4 to
the V.sub.cc terminal.
In this embodiment, resistors R2 and R3 have resistance values of
100 ohms and 150 K ohms, respectively, and capacitor C3 has a value
of 15 .mu.F. When operating in the non-synchronous (i.e.,
self-timed) mode, capacitor C3 is charged through resistors R3 and
R2 until it has charged to 2/3 V of the Zener voltage of diode D3.
During charging, the "OUT" Pin 3 of the timer is high, causing
transistor Q1 to conduct which, in turn, by reason of a connection
from its collector electrode to the gate electrode of SCR Q2, turns
the latter "Off". Once capacitor C3 has charged to 2/3 V, the
voltage at Pin 7 causes Pin 3 to go low, which initiates a
discharge cycle. Capacitor C3 discharges through resistor R2 only
until its voltage reaches 1/3 of the voltage on D3, which because
of the small resistance of R2 occurs in a very brief time period.
During this brief period, switch Q1 is turned "off" and applies a
pulse to switch Q2 to turn it "on" and the flashtube is fired The
timer provides greater control over the flash rate in the
non-synchronous mode than does the circuit shown in FIGS. 5,
potentially at less than 3 seconds intervals.
When operating in the synchronous mode, the timer U2 is in its
charging or "on" state; when a sync pulse arrives the D.C. power is
interrupted by Pin 4 (RESET) of the timer being pulled to ground
through the action of the series-connected resistor R7 and
capacitor C5, the potential at the junction of which is coupled to
Pin 4 (RESET) and also through diode D4 to the V.sub.cc terminal of
the timer. Grounding of Pin 4 resets the timer, turning switch Q1
"off" which, in turn, turns switch Q2 "on" to fire the flashtube.
Upon termination of the sync signal, which it will be recalled has
a period in the range from 10 to 30 milliseconds, capacitor C3 is
again charged through resistors R6, R3 and R2 to ready the timer
for arrival of the next sync signal. In case a sync signal does not
arrive 2.9 seconds later the timer will automatically go into the
described non-synchronous self-timed mode.
By way of example, the following parameters may be used for the
components of the FIG. 7 circuit, having a V.sub.in of 24 V D.C.,
to obtain the indicated flash frequencies:
ELEMENT VALUE OR NO. C1 CAP., 0.047 .mu.F, 400 V C2, C3 CAP., 15
.mu.F, 16 V C4 CAP., 0.01 .mu.F C5 CAP., 0.1 .mu.F C6 CAP., 47
.mu.F, 250 V D1 DIODE, 1N4007 D2 ZENER DIODE, 240 V D3 ZENER DIODE,
1N5239 D4 DIODE 1N914 D5 DIODE HER106 Q1 TRANSISTOR, 2N4401 Q2 SCR,
7 Q3 TRANSISTOR, IRF710 L1 INDUCTOR 8.7 mH R1 RES., 22 k R2 RES.,
100 R3 RES., 150 K R4, R5 RES., 10 K R6 RES., 4.7 K R7 RES., 10 K
R8 RES., 16.9 R9 RES., 33 K R10 RES., 220 K, 1 W R11 RES., 180, 1 W
U1 TIMER, KS555 U2 OPTCOUPLER, 4N35
FIG. 8 is a circuit diagram of a microcontroller strobe circuit
similar to that disclosed and claimed in applicants' copending
application Ser. No. 08/061,965 filed May 14, 1993, the flashing of
which also may be synchronized by the sync control circuit 18 of
FIG. 3. The circuit is connected across the D.C. voltage source,
supplied via the sync control circuit 18 as previously described,
having a voltage V.sub.in. The voltage is applied through a diode
D1, which typically has a voltage drop of 0.7 volt, to a regulator
which includes resistors R10, R11, R12 and R13, a switch Q2 and an
integrated circuit U1 for providing a regulated 5.00.+-.1% volts
input to the V.sub.cc terminal of a microcontroller U2. A precise
V.sub.cc input voltage is vital for the analog-to-digital reference
input of microcontroller U2. Resistors R10 and R11 are connected in
series between the cathode of diode D1 and the base electrode of
switch Q1, which in this case is a transistor, and also to the
cathode of integrated circuit U1, which acts as a controlled Zener
for providing 5.00 volts.+-.1%. Resistors R12 and R13 are connected
in series between the emitter of transistor Q2 and the negative
side of the voltage source, and their junction is connected to the
control electrode of integrated circuit U1. Resistors R12 and R13
are of equal value for biasing integrated circuit U1.
A reset circuit includes a diode D4, and a capacitor C5 connected
in series between the emitter electrode of switch Q2 and the
negative side of the D.C. source, and a resistor R3 connected in
parallel with diode D4. The junction between diode D4 and capacitor
C5 is connected to the "CLEAR" terminal of microcontroller U2. As
stated above, microcontroller U2 is supplied with a regulated 5
volt supply at V.sub.cc ; the V.sub.ss terminal is connected to the
negative side of the source. A capacitor C8 connected across
V.sub.cc and V.sub.ss acts as a filter. A resistor R7 connected
between one of the analog-to-digital input terminals (PAO, Pin 17)
of microcontroller U2 and the negative side of the source acts as a
shield for the controller. Oscillations at a frequency of 4 MHz are
applied to terminals OSC1 and OSC2 of the microcontroller by a
resonator circuit consisting of an oscillator Y1 and a pair of
capacitors C1 and C2 connected between the negative side of the
source and the first and second oscillator inputs,
respectively.
A voltage level proportional to the supply voltage, V.sub.in, is
supplied to a different analog-to-digital input terminal of the
microcontroller, for example, the PA1 terminal (Pin 18) by a
voltage divider network consisting of a potentiometer R15, a
resistor R9 and a resistor R4 connected in series between the
junction of diode D1 and resistor R10 and the negative side of the
D.C. source, and a capacitor C6 connected in parallel with resistor
R4. The voltage developed at the junction between resistors R9 and
R4, which may be fine-tuned by the potentiometer R15, is applied to
the PA1 terminal.
The microcontroller U2 controls the opening and closing of a switch
Q1, which in this embodiment is a MOSFET, by coupling a signal
developed at an output terminal PB3 (Pin 9) via a voltage divider
consisting of resistors R6 and R8 to the gate electrode of switch
Q1. Switch Q1 is connected in series with an inductor L1 and a
diode D2, and when closed connects the inductor across the voltage
source, V.sub.in. With switch Q1 closed, inductor L1 stores energy
until a steady state level is reached, or the switch is opened.
When switch Q1 is opened, the energy stored in inductor L1 is at
least partially transferred through a diode D3 and a resistor R14
to a storage capacitor C7 connected in parallel with a flashtube.
By controlling the opening and closing of switch Q1, the rate at
which energy is stored in inductor L1 is regulated, thereby
regulating the energy transferred to storage capacitor C7. Diode D3
permits current flow into the flash unit but prevents discharge of
capacitor C7 when the potential across it is higher than V.sub.in
or the potential across inductor L1. The flashtube is shunted by a
trigger circuit which includes a resistor R1 connected in series
with the combination of a switch Q3, which in this embodiment is an
SCR, connected in parallel with the series combination of a
capacitor C3 and the primary winding of an autotransformer, the
secondary winding of which is connected to the trigger band of the
flashtube. When, at the appropriate time, a signal produced at the
PA2 output of microcontroller U2 is applied via a resistor R5 to
the gate of the SCR (Q3), the SCR is fired and causes capacitor C3
to discharge through the primary winding of the transformer,
inducing a high voltage pulse in the secondary winding which
ionizes the gas in the flashtube and causes it to flash, provided
the voltage thereacross equals or exceeds the threshold firing
voltage. A resistor R2 connected between the gate electrode of the
SCR and the negative side of the D.C. supply isolates the SCR from
noise.
Microcontroller U2, which in this embodiment is a PIC16C71
microcontroller having a built-in analog-to-digital converter with
8-bit resolution, uses the A/D converter to arrive at a digital
equivalent of the supply voltage and then uses this digitized
information to control the opening and closing of switch Q1, and
thus the charging of inductor L1 and the transfer of energy from
the inductor to capacitor C7, so that the output PA2 triggers
switch Q3 to fire the flashtube at the same time that the potential
across the capacitor C7 has attained the desired value. More
particularly, the A/D converter measures the supply voltage in 256
steps of approximately 1/4 volt each. The microcontroller program
U2 equates each step with a location in a look up table. One
conversion or measurement is made for each cycle of the switch Q1,
a new value being read from the lookup table each time. These
values control the ON time of switch Q2. The ON time for each value
in the lookup table is empirically derived; for low voltages, the
ON time is long, and for high voltages, the ON time is shorter,
whereby the energy stored throughout a flash cycle is kept somewhat
constant.
The switching frequency of switch Q1 is in the range of
approximately 3 kHz to 30 kHz and has a high duty cycle (roughly
50% to 90%). Each value in the lookup table equates to a switching
frequency for ensuring that switch Q2 will be ON for sufficient
time to charge capacitor C7 to the precise amount needed for the
minimum required intensity of once per three seconds flash, for
example. The high duty cycle results in storing of the energy in
inductor L1 for most of the three seconds interval between flashes.
This means that peak currents are lower than if the routine
utilized a low duty cycle in which inductor L1 was charged for a
relatively shorter period during each flash cycle.
If the supply voltage sensed is below a minimum (e.g., less than 13
volts, below which it may be impossible to obtain the precise 5.00
volts.+-.1%) microcontroller U2 turns switch Q1 OFF and waits for
the level to rise above the preset start up voltage (e.g., 14
volts).
Microcontroller U2 has an interrupt, a real time clock and a
prescaler which are used to produce an accurate, one per three
seconds flash rate. The real time clock and prescaler generate a
one-fifteenth of a second interrupt. The interrupt service routine
then counts these pulses. When fifteen pulses have occurred, a
pulse is sent to the SCR Q3 and the flashtube is triggered. The
interrupt routine additionally controls the variable OFF time
function. The OFF time of switch Q1 is programmed to be a different
predetermined value dependent on the number of cycles completed in
the fifteen hertz rate of the interrupt (i.e., dependent on the
time since the last flash). A high value of OFF time is used after
a trigger event, followed by several progressively lower values.
This helps to minimize current anomalies during and immediately
after a flash.
By way of example, the following parameters may be used for the
elements of the FIG. 8 circuit to obtain a flash frequency of one
flash per three seconds:
ELEMENT VALUE OR NO. C1, C2 CAP., 33 pF, 200 V C3 CAP., .047 .mu.F,
400 V C5 CAP., 47 .mu.F C6 CAP., 1 .mu.F C7 CAP., 150 .mu.F, 250 V.
C8 CAP., 15 .mu.F, 16 V D1, D2 DIODE 1N4007 D3 DIODE HER106 D4
DIODE 1N914 L1 INDUCTOR, 8.7 mH Q1 TRANSISTOR, IRF740 Q2
TRANSISTOR, 2N5550 Q3 SCR. EC103D R1 RES., 220 K R2 RES., 10 K R3
RES., 39 K R4, R5 RES., 1 K R6 RES., 220 R7 RES., 100 R8 RES., 100
K R9 RES., 11.3 K R10 RES., 330 R11 RES., 4.7 K R12, R13 RES., 10 K
R14 RES., 120 R15 POT., 1 K T1 TRANSFORMER, TRIGGER U1 LC., TL431A
U2 LC., PIC16C71 Y1 CERAMIC RES., 4 MHz
While up to this point the invention has been described in
association with a fire alarm system including a fire alarm control
panel which controls multiple strobes connected in a single loop,
conventional fire alarm control panels may, and often do, control
more than one loop of multiple strobes. The several loops may, for
example, be installed in different zones or sections of a building,
in which case it would not be necessary to synchronize flashing of
the strobes in all of the loops, but in other situations it may be
desirable to synchronize flashing in one or more of loops
presenting an alarm condition. The control unit illustrated in FIG.
3 could not by itself perform these functions, yet in the interest
of cost it is desirable to avoid having to provide a separate
controller for each of the loops. The control circuit shown in
FIGS. 9 and 10 enables one microcontroller to control up to four
separate loops or zones, and may be expanded to control one or more
additional controllers each capable of controlling an additional
four loops of strobes. Referring to FIGS. 9 and 10, in which
components common to FIG. 3 are correspondingly identified, a
single microcontroller U2, which may be a PIC16C54, is capable of
controlling up to four loops of strobes (not shown) which are
connected to the positive and negative OUTPUT terminals of four
relay circuits labeled ZONE 1, ZONE 2, ZONE 3 and ZONE 4,
respectively. When and only when an alarm condition is present in a
zone, a D.C. voltage, typically 24 volts, is applied across its
positive and negative INPUT terminals, and a relay K connected to
the positive terminal when in the condition shown in FIG. 9,
supplies this voltage to the strobes connected in a loop to that
zone. As will be described presently, the microcontroller U2
produces signals at its output pins 6, 7, 8 and 9 which are applied
to control circuitry in ZONES 1, 2, 3 and 4, respectively, which
momentarily open a corresponding relay K, for a period of 10-30
milliseconds, thereby interrupting power to and triggering flashing
of the strobes powered through that relay.
Referring in detail to FIG. 9 and the ZONE 1 circuitry, the
positive side of the D.C. input voltage is coupled through a diode
D10 to a terminal labeled "V+" and a negative side is coupled
through a diode D12, the emitter-collector path of a bipolar NPN
transistor Q4 and a diode D14 to a terminal labeled "V-". A
potential exists between these V+ and V- terminal only when a D.C.
potential, V.sub.in, is applied to the ZONE 1 input terminals. The
same is true of the ZONE 2, ZONE 3 and ZONE 4 circuits, namely,
that a potential appears across their V+ and V- terminals when, and
only when, a D.C. potential indicating an alarm condition is
applied to their input terminals. The terminals labeled "V+" in all
four zones are actually internally connected together and to a
similarly labeled terminal of a power regulator circuit (FIG. 10)
and the terminals labeled "V-" in all four zones are internally
connected together and to the negative side of the power regulator
circuit. Thus, a potential is applied across the "V+" and "V-"
terminals of the power regulator only if one or more of the four
zones is energized.
To enable the microcontroller to determine which of the four zones
is energized, particularly when more than one are energized at the
same time, each is isolated from the others by an isolation circuit
including the aforementioned diodes D10, D12, D14 and transistor Q4
and a resistor R15 connected between the positive side of the D.C.
input voltage and the base electrode of transistor Q4. Diode D10 is
a blocking diode which prevents current flow from the
commonly-connected "V+" terminals to other zones and also prevents
current from such common circuit from forward-biasing transistor Q4
when a zone, say ZONE 1, is energized. The negative side of the
input D.C. is coupled via diode D12, transistor Q4 and another
diode D16 onto a respective ZONE INPUT line to a respective one of
four inputs to microcontroller U2 labeled PB0, PB1, PB2 and PB3,
respectively. Each of these ZONE INPUT lines is connected via a
respective resistor R to a regulated +5.00 volts supply (to be
described) and via a respective capacitor C to the negative side of
the supply.
Regulated voltages for operating the system are supplied by the
POWER REGULATORS shown in FIG. 10 when, and only when, one or more
of the zones are actuated so as to provide a potential, typically
24 volts, between the internally connected terminals labeled "V+"
and "V-". A voltage of 5.0 volts .+-.1% is produced at an output
terminal labeled "+5 V" by a regulator which includes a diode D1,
resistors R4 and R5 and an integrated circuit U1 which acts as a
controlled Zener, connected in series in that order from the V+
terminal to the V- terminal of the supply, a transistor Q1 having
its base electrode connected to the junction of resistor R5 and
integrated circuit U1, its collector connected to the junction of
resistors R4 and R5, and its emitter connected through
series-connected resistors R7 and R6 to the V- terminal of the
power supply. The junction of resistors R6 and R7 is connected to
the control pin of integrated circuit U1. A regulated potential of
5.0 volts produced at the emitter of transistor Q1 is filtered by a
capacitor C8, and applied via an internally connected terminal,
also labeled "+5 V" to the V.sub.cc input of the microcontroller.
The V.sub.ss input of the controller is connected to the V-
terminal of the power supply.
A regulator for producing a potential of 12 volts required for
operation of ZONE and EXPANSION relays includes a resistor R8 and a
Zener diode D4 connected in series across the supply, and a
Darlington transistor pair Q3 connected in parallel with resistor
R8 and in series with a filter capacitor C9. The regulated 12 volts
produced at the output emitter of the Darlington pair appears at a
terminal labeled "+12 V" which is internally connected to a
similarly labeled terminal in each of the ZONE circuits and also in
the EXPANSION circuit. It is again emphasized that the controller
is powered only when at least one ZONE is energized.
The clock frequency of the microcontroller is determined by a 4 MHz
resonator Y1 and a pair of capacitors C1 and C2 connected to the
OSC1 and OSC2 terminals, respectively, of the controller. When
energized upon the occurrence of an alarm condition in a ZONE, the
microcontroller is programmed to monitor the ZONE INPUTS and
ascertain which of them is activated, and then toggles a relay K in
the circuitry for the corresponding ZONE for a period in the range
from 10 to 30 milliseconds, thereby briefly interrupting the
application flow of power to the strobes associated with that
ZONE.
More particularly, and assuming that the microcontroller has sensed
that ZONE 1 has been energized, after a delay of 2.9 seconds
following initial sensing of the alarm condition, a +5.00 volts
signal is produced at output terminal PA0 (Pin 17) and coupled via
a respective RELAY OUTPUT line to the gate electrode of a MOSFET Q5
via a voltage divider including resistors R16 and R17 connected in
series and to the terminal "V-". The junction of resistors R16 and
R17 is connected to the gate electrode of Q5, the source and drain
electrodes of which are connected in series with the coil of relay
K across the power supply represented by terminals "V+" and "V-".
When switch Q5 is turned "ON" by the signal from Pin 17, relay K is
activated, thereby interrupting power flow to the strobes for a
short, hardly noticeable, interval. An optional diode D18 connected
across the relay coil suppresses the reverse EMF spike that is
generated when switch Q5 is opened, but may be omitted in the
interest of increasing the switching speed of the relay.
If, for example, the controller also senses an alarm condition in
ZONE 4, a +5.00 volts signal is also produced at output terminal
PA3 (Pin 2) which turns "ON" the MOSFET and actuates the relay K in
the ZONE 4 circuit in synchronism with actuation of the relay in
the ZONE 1 circuit, whereby the strobes in the loops associated
with both zones will be fired at the same time. Alternatively, to
preclude the creation of possible anomalies in current flow that
might result from all strobes in the four loops flashing at the
same time, the microcontroller may be programmed to interrupt the
power in the four loops at staggered times within the 2.9 seconds
interval. That is to say, the 2.9 seconds interval may be divided
into four time slots of approximately 0.75 second each in which
triggering of the four zones is initiated sequentially. The
flashing would be harmonious, if not synchronous, but would meet
Underwriters Laboratories' specifications for flash rates.
In accordance with another aspect of the invention, synchronized
firing of the strobes in more than four loops can be controlled by
providing the controller with an EXPANSION circuit having EXPANSION
INPUT and EXPANSION OUTPUT terminals, as shown in the lower
right-hand portion of FIG. 10, which are connected in "daisy-chain"
fashion as depicted in FIG. 13, to the EXPANSION INPUT and
EXPANSION OUTPUT terminals of one or more similarly equipped
controller of the kind just described, each for controlling four
loops of flash units. More particularly, the expansion output
terminals of a first controller, labeled "CONT. #1" are connected
to the expansion input terminals of a second controller, CONT. #2,
the expansion output terminals of which are connected to the
expansion input terminals of a third controller, and so on, with
the expansion output terminals of the last controller of the chain
connected back to the expansion input terminals of the first. By
connecting multiple controllers in this way, sync signals generated
by one controller in the chain as a consequence of an alarm
condition occurring in at least one of its associated ZONES, may be
transferred to the other controllers in the chain. Because each of
the interconnected controllers is equally likely to experience an
alarm condition, and there is no way of knowing when, if ever, a
particular controller will be energized by occurrence of an alarm
condition, the EXPANSION circuit of each controller must be able to
transfer sync signals from the EXPANSION INPUT terminals to the
EXPANSION OUTPUT terminals whether the controller is powered or
not.
To this end, the EXPANSION circuit includes a relay K, the coil of
which is connected between the "+5 V" and "V-" terminals of the
microcontroller and shunted by a diode D20 for suppressing the back
EMF spike created when current through the coil is turned off. In
the event of no power on any of the four zones, with the
consequence that the microcontroller U2 is not energized, the relay
contacts are in the illustrated non-energized position and
accordingly by-pass the controller. That is, contact 2 and
contactor 3 and contact 9 and contactor 8 respectively directly
connect positive and negative EXPANSION INPUT terminals to positive
and negative EXPANSION OUTPUT terminals.
however, when an alarm condition occurs in at least one ZONE to
cause powering of the controller, current flows through the relay
coil from the +5 V bus to the negative side of the supply and
actuates the relay, whereby a +12 V potential is coupled through
contact 4 and contractor 3 to the positive EXPANSION OUTPUT
terminal and the drain electrode of a MOSFET Q6 is coupled through
contact 7 and contactor 8 to the negative EXPANSION OUTPUT
terminal, and the positive and negative EXPANSION INPUT terminals
are both disconnected. As a consequence the relay K no longer
by-passes the controller to transfer any sync signal generated by
another controller in the chain and appearing on the EXPANSION
INPUT line to the next successive controller. The by-pass function
is restored by a circuit including an optocoupler U3, the light
emitting diode of which is connected in series with a resistor 22
across the EXPANSION INPUT lines, and the transistor output portion
of which is connected in series with a resistor R23 between the "+5
V" and "V-"terminals of the POWER REGULATORS. The junction between
resistor R23 and the collector of the transistor is connected to
terminal PB6 (Pin 12) of controller U2. If at least one ZONE
associated within another interconnected controller is energized,
there will be a 12 volt D.C. potential across the EXPANSION INPUT
lines, causing the optocoupler diode to conduct and turn "on" the
transistor portion. Conduction of the transistor portion pulls the
potential on Pin 12 of the controller from +5 V to zero, which the
controller is programmed to sense and cause terminal PB7 (Pin 13)
to go "high". This voltage pulse is applied to the gate electrode
MOSFET Q6 via a voltage divider including resistors R18 and R20,
which turns Q6 "on" and causes current flow in the diode portion of
the optocoupler connected to the EXPANSION INPUT terminals of the
next controller in the chain. Thus, when the controller is powered,
the "expansion" sync signal is received through the optocoupler and
under control of the microcontroller is forwarded via switch Q6 to
the next controller.
Referring now to the flow chart of FIG. 12, following START the
controller initially turns "off" all relays, that is, the relay in
each of the ZONE circuits, and also turns "OFF" the "expansion
output pulse" to MOSFET Q6. Following a short delay of about 1
second, a counter is started which counts for about 2 seconds after
which Pin 12 is read to determine whether it is at +5 volts,
indicating no expansion input, or zero in case there is an input.
If the answer is "No" the count of the counter is checked to
ascertain whether the 2 seconds has elapsed and, if not, pin 12 is
again read. A "Yes" decision from either diamond turns "ON" the
expansion output pulse to MOSFET Q6 to pass a signal on to the next
controller. Then, the four zone inputs (Pins 6, 7, 8 and 9) are
scanned to determine which is "ON" or energized; it will be
recalled that at least one must be on, otherwise there will be no
operating power for the controller. When the "ON" zone or zones
have been identified, a relay output signal is applied to and turns
on the corresponding zone relays and thereby interrupt power to the
associated loop-connected strobes for a short period, in the range
from 10 to 30 milliseconds, following which the cycle is
repeated.
As noted earlier, to preclude the creation of possible anomalies in
current flow that might result should all of the strobes in all of
the loops be flashing at the same time, the microcontroller may be
programmed to interrupt the power supplied to the loops at
staggered times within the 2.9 seconds interval. Referring to the
simplified flow chart of FIG. 14 which outlines the program,
following START the controller initializes parameters and then
turns "off" all relays, namely, the relay in each of the ZONE
circuits, and also turns "OFF" the "expansion output pulse" to
switch Q6. Following a short delay of about 60 milliseconds, a
counter is started which counts for about 3/4 second after which
Pin 12 is read to determine whether it is at 5 volts indicating no
expansion pulse input, or zero in case there is an input. If the
answer is "No" the count is checked to ascertain whether the 3/4
second has elapsed and if not, Pin 12 is again read. A "Yes"
decision from either diamond turns on the expansion output pulse to
switch Q6 to pass a sync signal to the next controller. Then a
first of the four zone inputs (e.g., Pin 6) is scanned to determine
if it is "ON" and if energized, a relay output signal is applied to
and turns on that zone relay and thereby interrupts power to the
associated strobes for a period in the range from 10 to 30
milliseconds. Next the microcontroller repeats the process
successively scanning the remaining three zone inputs and applying
relay output signals to appropriate zone relays. The net result is
that the energized flash units in the four zones are triggered
sequentially at 3/4 second intervals within a period of about 3
seconds.
* * * * *