U.S. patent number 3,575,640 [Application Number 04/777,253] was granted by the patent office on 1971-04-20 for automatic water supply system.
This patent grant is currently assigned to Omron Tateisi Electronics Co.. Invention is credited to Tadayuki Ishikawa.
United States Patent |
3,575,640 |
Ishikawa |
April 20, 1971 |
AUTOMATIC WATER SUPPLY SYSTEM
Abstract
An automatic water supply control system for a toilet facility,
wash basin or the like which features a capacity-sensitive antenna
positioned to sense the approach of a user and cause a valve
actuator signal to be produced, coupled with a circuit for
compensating for slow changes in antenna capacity caused by changes
in ambient conditions, such as humidity. The system includes timing
and delay circuitry which permit the system to allow for minor
movements of the user adjacent to the facility and to shut off
after a predetermined period of operation.
Inventors: |
Ishikawa; Tadayuki (Kyoto,
JA) |
Assignee: |
Omron Tateisi Electronics Co.,
(Kyoto, JA)
|
Family
ID: |
13601837 |
Appl.
No.: |
04/777,253 |
Filed: |
November 20, 1968 |
Foreign Application Priority Data
|
|
|
|
|
Nov 27, 1967 [JA] |
|
|
42-76312 |
|
Current U.S.
Class: |
361/181; 4/313;
361/203; 4/304; 4/623 |
Current CPC
Class: |
H03K
17/955 (20130101); H03B 5/1243 (20130101); H03B
5/1203 (20130101); H03B 5/1296 (20130101); H03B
5/1231 (20130101); H03B 2200/0066 (20130101); H03K
2017/9606 (20130101); H03B 2200/0034 (20130101) |
Current International
Class: |
H03K
17/94 (20060101); H03B 5/12 (20060101); H03B
5/08 (20060101); H03K 17/955 (20060101); H01h
047/12 () |
Field of
Search: |
;4/1,100,101
;317/146,148.5 ;251/129 ;340/258 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: O'Dea; William F.
Assistant Examiner: Smith; Robert I.
Claims
I claim:
1. An automatic water supply control system for a toilet facility
or the like comprising:
a. a detector circuit including a capacity-sensitive antenna
positioned to respond to the approach of a user of the facility and
means responsive to a change in antenna capacity to produce an
output signal;
b. a compensator circuit coupled to said detector circuit and
including means sensitive to the rate of change of said output
signal and operable in response to rates of change below a
predetermined rate to cancel said change and maintain said output
signal at a predetermined level;
c. water valve control means;
d. means for actuating said valve control means including circuit
means operable in response to output signal changes not cancelled
by said compensating circuit to produce a valve actuating signal;
and
e. means responsive to said valve actuating signal for deactivating
said compensator circuit.
2. The system of claim 1 further including delay means coupled to
said deactivating means to maintain the same in its deactivating
condition for a predetermined period following termination of said
valve actuating signal.
3. The system of claim 1 further including timing means triggered
by said valve actuating signal and operable after a predetermined
period of delay to reactivate said compensator circuit.
4. The system of claim 3 further including delay means coupled to
said deactivating means to maintain the same in its deactivating
condition for a predetermined period following termination of said
valve actuating signal.
5. The system of claim 4 wherein said deactivating means comprises
a relay having a normally closed contact coupled between said
detector and compensator circuits, said relay being energized by
said actuator signal to open said contact.
6. The system of claim 5 wherein said reactivating means comprises
means responsive to termination of said valve actuating signal to
deenergize said relay and a delay circuit coupled to said relay to
delay deenergization thereof for said predetermined period.
7. The system of claim 5 wherein said reactivating means comprises
an RC circuit charged toward a predetermined voltage level in
response to said activating signal, and circuit means coupled to
the detector circuit and operable when said RC circuit becomes
charged to said voltage level to produce a detector circuit output
signal corresponding to the absence of a user of said facility,
thereby deenergizing said relay and reactivating said compensator
circuit.
8. The system of claim 3 wherein said compensator circuit includes
a capacitor charged to a level determined by the capacity of said
antenna for its ambient conditions, and means for maintaining said
level of charge during the period of deactivation of said
compensator circuit.
Description
This invention relates to an automatic water supply system and,
more particularly to an apparatus operable in response to the
electrostatic capacity of an object approaching thereto such as a
human body or hands to flow water.
Such automatic water supply systems generally include a proximity
detector which may comprise a high frequency oscillating circuit,
one of the component parts of which is the antenna provided
adjacent a wash basin, a stool or a urinal. When a human body or a
portion thereof enters the field of the antenna, the oscillating
condition of the oscillator changes. Therefore, the presence or
absence of a human body or hands can be detected by such a change
in the oscillating output of the oscillator. When a human body or
hands enter the field of the antenna, the electrostatic capacity of
the antenna changes, with a resulting change in the oscillating
output of the oscillator. The electrostatic capacity of the
antenna, however, is changed by other causes than the approach
thereto of a human body or a portion thereof, so that sometimes the
system will erroneously operate in the absence of any user of the
toilet. Moisture may be the most important among such other causes,
and a toilet is a place which is very likely to be exposed to
moisture.
In order to prevent the erroneous operation of the system caused by
change in the ambient conditions, it is well known to provide the
oscillator with a compensating circuit having a delay element.
Generally, Generally, the change in the oscillating output
condition of the oscillator caused by change in the ambient
condition takes place far more slowly than that caused by the
approach or removable of a human body or a portion thereof. To put
it in detail, when a human body approaches the antenna, the
oscillating condition of the oscillator changes within the delay
time provided by the delay element, whereas when the ambient
condition, say, the humidity of the air around the antenna changes,
the oscillating condition of the oscillator continues changing even
after lapse of the delay time. Therefore, in the former case, the
change in the oscillating condition of the oscillator finishes
before the compensating circuit operates, so that the presence of a
human body in the antenna field can be detected. In the latter
case, however, the compensating circuit operates in response to the
change in the oscillating output condition of the oscillator.
Therefore, if the arrangement is such that upon operation of the
compensating circuit, the oscillating output of the oscillator is
fed back to the oscillator to compensate for any change in the
oscillating output level, the oscillating output condition remains
substantially unchanged, regardless of the change in the ambient
condition, so that the system will not unnecessarily operate.
A new problem, however, has been posed by the provision of such a
compensating circuit. Suppose that after the antenna has detected
the body or hands of a user, the user continues to stay there in
the field of the antenna even after lapse of the delay time
provided by the delay element in the compensating circuit. The
compensating circuit will then operate as if there were no human
body in the field of the detector. This certainly is very
inconvenient.
The problem may be solved by so arranging that when the detector
has detected a human body or portions thereof, the compensating
circuit will not operate. However, this is not a perfect solution.
In the case of a wash basin, for example, water must flow when
hands are positioned below the faucet (that is, near the antenna)
and then stop when the hands are removed therefrom. If the user has
left the basin, however, forgetting a handbag or something placed
near the faucet, water continues to flow out. In the case of a
stool or a urinal, the arrangement must be such that the stool or
urinal must be flushed after use. However, if the user has left the
place, forgetting a baggage or something placed near the antenna,
no water will flow. This is a very foul, insanitary and offensive,
In short, the problem can not be solved by the prior art
arrangement that the compensating circuit is rendered inoperative
upon actuation of the detector.
Accordingly, it is one object of the invention to provide an
automatic water supply system for the toilet or the like including
an oscillator and a compensating circuit, wherein when the ambient
condition of the detector changes, the compensating circuit
operates to compensate for any change in the oscillating output of
the oscillator thereby to prevent water from flowing out, whereas
upon detection of an object to be detected such as a human body or
hands, the compensating circuit is rendered inoperative.
Another object of the invention is to provide such an automatic
water supply system as aforesaid, wherein if the object detecting
condition of the system lasts longer than a predetermined period of
time, for example, the period of time required for using a wash
basin, a stool or a urinal, the nonobject detecting condition of
the system is forcedly restored.
The system of the invention comprises a detecting circuit such as
an oscillator, the output condition of which varies upon entrance
of an object to be detected into the field of a capacity sensitive
antenna included in the oscillator, and a compensating circuit so
arranged that the output of said detecting circuit is fed back to
the detecting circuit to compensate for any change in the output
thereof caused by the capacity change of the antenna. The
compensating circuit includes a delay element having a time
constant longer than that required for a change to occur in the
output of the detecting circuit due to entrance of an object to be
detected into the field of the antenna. The detection signal from
the detecting circuit, that is, the above-mentioned change in the
output thereof, is used to actuate a detection signal responsive
circuit to produce a signal for actuating a control circuit for a
valve thereby to make water flow out.
On the other hand, upon actuation of the detection signal
responsive circuit, the compensating circuit is rendered
inoperative. So long as the compensating circuit is kept
inoperative, it never happens that the detection signal from the
detecting circuit is caused to disappear by the operation of the
compensating circuit despite the presence of an object in the field
of the detector.
Any change in, say, the moisture content of the air around the
detector may result in a change in the output of the detecting
circuit, but such an output change gradually takes place so that
the delay time provided by the delay element in the compensating
circuit elapses before the output change of the detecting circuit
reaches a level sufficient to actuate the detection signal
responsive circuit. Consequently, the compensating circuit operates
to compensate for such change in the output of the detecting
circuit. This means that no detection signal is produced by the
detecting circuit when moisture or other ambient conditions have
changed the capacity of the antenna.
The system of the invention is also provided with a timer arranged
to begin operating when the compensating circuit is rendered
inoperative. The delay time provided by the timer is set to a
predetermined period of time which is longer than the period of
time required for the use of a wash basin, a stool or a urinal. In
the case of a wash basin, the delay time may be set to 30 seconds
and in the case of a stool or a urinal, it may be set to 2 to 5
minutes.
When the delay time is up, the operative condition of the
compensating circuit is restored so that the detection signal from
the detecting circuit is caused to disappear despite the object
existing within the field of the detector.
The timer is provided for the following reason: To take a wash
basin for example, when a user's body approaches the antenna, water
flows out of the faucet and the compensating circuit is rendered
inoperative. When the body is moved away from the field of the
antenna, the flowing water stops. Suppose, however, that the user
happens to have placed a handbag or something near the antenna and
has gone out of the place, leaving the handbag there. The system
will then operate as if it were still detecting the body so that
water continues flowing out even after the user has left the basin.
However, this condition lasts only 30 seconds after water started
to flow out until the delay time is up, whereupon the compensating
circuit is restored to the operative condition so that the flowing
water is stopped.
In the case of a stool or a urinal, when the antenna detects a
human body, the stool or urinal is initially flushed for a
predetermined period of time, and at the same time the compensating
circuit is rendered inoperative. When the person has left the place
after use, the detection signal disappears so that the stool or
urinal is again flushed for a predetermined period of time.
However, if the user has gone out without taking up a bag or
something placed near the antenna, the detecting signal continues
so that the stool or urinal is not flushed again. However, when the
delay time is up, that is, 2--5 minutes after the initial flushing,
the compensating circuit is restored to the operative condition to
cause the stool or urinal to be flushed again.
The invention will be better understood from the following detailed
description of preferred embodiments thereof with reference to the
accompanying drawings, wherein like reference symbols and numerals
denote corresponding parts and wherein:
FIG. 1 is an electrical circuit diagram of one embodiment of the
invention;
FIG. 2 is a diagram similar to FIG. 1 but showing a different
embodiment of the invention;
FIG. 3 is a block diagram of part of still another embodiment of
the invention;
FIG. 4 is a schematic perspective view of a urinal to which the
invention is applied; and
FIG. 5 is a schematic side view of a wash basin to which the system
of the invention is applied.
Now referring to the drawings, first to FIG. 1, there is shown a
detecting circuit in the form of an oscillator 10 of the Coplitts
type comprising a plurality of condensers, resistors, and
inductance coils and a transistor Trl. In a condenser circuit of
the oscillator there are connected a variable capacity diode CV and
a capacity sensitive, object detecting antenna 12. The diode CV and
the antenna 12 provide part of the capacity required for the
oscillating circuit. The diode CV receives a control voltage from a
compensating circuit to be described below, so that when the
voltage thereon increases, the capacity of the diode decreases,
with a resulting decrease in the amplitude of the oscillating
output of the oscillator 10, and vice versa. On the other hand,
when an object such as a human body or a portion thereof enters the
field of the antenna 12, its capacitance increases so that the
oscillating output condition changes whereby the amplitude of the
output of the oscillator decreases. The antenna 12 may be mounted
on the front wall of a casing 16 containing the various component
elements of the system and disposed above a urinal 14 as shown in
FIG. 4. The antenna may also be provided in the front wall of a
basin 18 fixed to a wall 24 of a room as shown in FIG. 5. A faucet
18 is disposed over the basin, at the bottom of which there is a
drain pipe 20. In this instance, the casing 16 may be fixed to the
drain pipe with a lead line 22 connecting the antenna to the
circuit in the casing 16.
The oscillating output from the oscillator 10 is applied to an
amplifier 30 comprising a transistor Tr2 through a transformer T
and a rectifier comprising a condenser C1 and a diode D1, so that
the amplifier 30 produces a direct current voltage corresponding to
the oscillating output of the oscillator 10. The amplified output,
that is, a detection signal appears at a terminal a. To this
terminal there is connected a compensating circuit 32 including a
condenser C2, charging resistors R1 and R2, and a normally closed
contact S1. The terminal voltage of the condenser C2 is impressed
through a line L1 across the previously mentioned variable capacity
diode CV.
To the terminal a there is also connected a line L2 leading to a
detection signal responsive circuit 34, so that a voltage at the
terminal a is applied as an input to the circuit 34. The circuit 34
includes a pair of transistors Tr3 and Tr4. A line L3 is connected
to the collector of the transistor Tr4 so that the collector
voltage appears on the line L3 as a control signal so to be used to
open a valve as will be described later in detail.
When the transistor Tr4 becomes nonconductive upon entrance of a
human body in the field of the antenna, a condenser C3 is instantly
charged through a resistor R3. The condenser C3 is connected in
parallel with a resistor R4 to form a delay circuit. When the
condenser C3 has been charged to a predetermined voltage level, a
transistor Tr5 is rendered conductive, thereby energizing a relay
RY. The previously mentioned contact S1 in the compensating circuit
32 is one of the three contacts of this relay RY, the other
contacts being a normally open contact S2 and a second normally
closed contact S3. These latter two contacts control the operation
of a timer 38 included in a timer circuit 36. The timer 38
comprises a condenser C4 and a charging resistor R5, and the delay
time provided by the timer 38 may be 30 seconds for a wash basin
and 5 or 2 minutes for a stool or urinal.
When the relay RY is energized, the contact S3 is opened and the
contact S2, closed so that the condenser C4 begins to be charged
through the resistor R5. When the relay RY is deenergized, the
contact S3 is closed again so that the condenser C4 instantly
discharged through a resistor R6.
The timer circuit 36 includes another timer consisting of a
monostable multivibrator 40 made up of a pair of transistors Tr6
and Tr7 with a condenser and resistors. The terminal voltage of the
condenser C4 is applied to the base of the transistor Tr6.
When the monostable multivibrator 40 operates, that is, when the
transistor Tr7 becomes nonconductive, the circuit 40 produces an
output voltage to be applied to the base of a transistor Tr8
constituting a gate circuit 42 to render the transistor Tr8 has its
emitter grounded and its collector connected through a line L4 to
the base point b of the previously mentioned transistor Tr5.
Therefore, when the transistor Tr8 becomes conductive, the base
voltage of the transistor Tr5 is reduced to the ground potential,
so that the transistor Tr5 is forcedly rendered nonconductive.
Now suppose that it is a urinal the flushing of which is to be
controlled. The signal So on the line L3 is applied to an on-off
delay timer 44. If the signal So continues for a less period of
time than the delay time provided by the timer 44, such as when a
person merely passes by the urinal, the timer 44 does not respond
to the signal So, thereby preventing the urinal from being flushed
by such an occasional passerby. On the contrary, when the signal So
lasts longer than the delay time, the timer 44 produces an output
to be applied to an amplifier 56 through a differentiator 46 and a
monostable multivibrator 48 on the one hand and through a NOT
element 50, a differentiator 52 and a monostable multivibrator 54
on the other. The output from the amplifier 56 energizes an
electromagnetic valve 58 to flush the urinal.
Normally, the compensating circuit 32 operates in the following
manner: When the ambient conditions of the antenna change, the
capacity thereof varies relatively slowly as previously mentioned.
The change in the antenna capacity results in a corresponding
change in the amplitude of the oscillating output of the oscillator
10 and, consequently, the output voltage at the terminal a. Let if
be assumed that the humidity in the atmosphere surrounding the
antenna 12 has decreased. This reduces the antenna capacity so that
the voltage at the terminal a increases. The increased voltage
charges the condenser C2 through the normally closed contact S1,
resistors R1 and R2, so that the terminal voltage of the condenser
C2 increases. This results in a corresponding increase in the
voltage impressed across the variable capacity diode CV with a
resulting decrease in the capacity of the diode CV. This causes the
amplitude of the oscillating output of the oscillator 10 and,
consequently, the voltage at the terminal a to decrease to the
original potential level. It will be easily seen that if the
capacity of the antenna gradually increases so that the voltage at
the terminal a decreases, this change is compensated for in the
manner opposite to that described just above. Thus, any gradual
change in the potential level at the terminal a caused by the
change in the ambient conditions of the antenna 12 can be
compensated for completely.
When a person approaches the urinal 14 to use it, the capacity of
the antenna increases so that the voltage at the terminal a
decreases. This change takes place more rapidly than that caused by
the gradual change in the ambient conditions of the antenna 12.
Therefore, before the condenser C2 is sufficiently discharged to
increase the capacity of the variable capacity diode CV, the
decreased voltage at the terminal a enters as a detection signal
the detection signal responsive circuit 34 via the line L2 so as to
render the transistor Tr4 nonconductive. This causes the signal So
to appear on the line L3 to be applied to the on-off delay timer
44. The output from the timer 44 is applied to the amplifier 56
through the differentiator 46 and the monostable circuit 48. The
amplified output from the amplifier 56 energizes the solenoid 58 to
open the valve for the urinal 14. Thus, when a person stands in
front of the urinal, water flushes it for a period of time as
determined by the output pulse width of the monostable
multivibrator 48.
The collector voltage of the transistor Tr4 also charges the
condenser C3 and at the same time renders the transistor Tr5
conductive, thereby energizing the relay RY. This opens the closed
contact S1 in the compensating circuit 32, thereby breaking the
connection between the circuit 32 and the terminal a. This renders
the compensating circuit 32 inoperative, so that the condenser C2
therein is neither further charged or discharged, but maintained at
the potential level of the terminal a before the approach of the
user to the urinal.
When the person has left the urinal within the delay time provided
by the timer 36, the oscillating output of the detecting circuit 10
is restored to the original amplitude, so that the voltage at the
terminal a is raised to the original level. This causes the
transistor Tr4 to become conductive and, consequently, the signal
So to disappear, whereupon the NOT element 50 produces an output to
be applied to the differentiator 52. The output pulse from the
differentiator 50 triggers the monostable multivibrator 54 to
produce an output of a predetermined pulse width. This pulse is
amplified by the amplifier 56 to energize the electromagnetic valve
58, which flushes the urinal 14 for a posterior cleaning.
When the signal So disappears, the relay RY is deenergized to close
the contact S1 again, thereby connecting the compensating circuit
32 between the terminal a and the variable capacity diode CV to
restore the operative condition of the circuit 32.
It must be mentioned, however, that when the signal So disappears,
the relay RY is not instantly deenergized but only after lapse of
the delay time provided by the delay element consisting of the
resistor R4 and the condenser C3. The delay element is provided for
the following reason: While a person is using a urinal, his body
does not always remain stationary but moves to and fro due to, say,
breathing. In other words, the distance between the antenna 12 and
the body of the user always varies. On the other hand, if the
detector has a very high degree of sensitivity, when a person
approaches the antenna to operate the system (with the voltage at
the terminal a dropping from, say, 6 volts to zero volt and the
voltage on the condenser C2 being maintained at the level of 6
volts) and then moves a little away from the antenna, the voltage
at the terminal a may increase from zero volt to, say, 1 volt. This
may cause the transistors Tr3 and Tr4 to become conductive so that
the relay RY would be deenergized to close the contact S1. As a
result, the condenser C2 that had until then maintained at 6 volts
would be discharged to about 1--2 volts, thereby increasing the
capacity of the diode CV and consequently the voltage at the
terminal a to the previous high level of 6 volts. Then the system
would no longer respond to the body even when it moves again into
the previous position near the antenna. In other words, the system
would not work any longer unless the body approaches nearer to the
antenna than it was when the system initially operated.
The positional change of the body while a person is using a urinal,
however, usually does not last very long, but ends in a fraction of
time. That is, the user's body will soon occupy the original
position in the field of the antenna again. Therefore, if the delay
time provided by the timer comprising the resistor R4 and condenser
C3 is set to a period of time a little longer than that generally
required for such positional restoration of the user's body, such
positional change of body relative to the antenna will not cause
the compensating circuit 32 to operate, so that the above-mentioned
defect is eliminated.
Suppose that a user has happened to place a bag or something near
the antenna. If the owner has gone out of the place, leaving the
bag there within the antenna field, the signal So continues to
exist on the line L3, so that water continues flowing out or the
urinal will not be flushed posteriorly. To avoid this, the system
of the invention is so arranged that the signal So is forcedly
caused to disappear after a predetermined period of time, whether
the user has left the urinal or not. This is accomplished by
providing a timer circuit 36 including a timer 38 and a monostable
multivibrator 40. The timer 38 comprises a condenser C4 and a
resistor R5; and the monostable multivibrator 40, a pair of
transistors Tr6 and Tr7.
When the relay RY is energized upon detection of a person, the
relay contact S2 is closed so that the condenser C4 is charged
through a resistor R5 until the charged voltage of the condenser C4
reaches a predetermined level, whereupon the transistor Tr6 is
triggered to become conductive. This renders the transistor Tr7
nonconductive, so that the transistor Tr8 of the gate circuit 42
becomes conductive. The conduction of the transistor Tr8 results in
a sudden drop of voltage at the base point b of the transistor Tr5
to substantially zero potential. This renders the transistor Tr5
nonconductive, so that the relay RY is deenergized to close the
contact S1, whereupon the compensating circuit 32 is restored to
the operative condition. The operation of the compensating circuit
32 causes the voltage at the terminal a to increase, just as in the
case where the ambient conditions of the antenna change, thereby
bringing the detecting circuit 10 to the nonobject detecting
condition, that is, as if there were nothing to be detected within
the field of the antenna 12. The circuit 40 is so designed that its
metastable state lasts for a period of time during which the
operation of the compensating circuit 32 is finished, whereupon the
circuit 40 is restored to its stable state.
If the system of FIG. 1 is to control a wash basin, the signal So
may be directly applied to the amplifier 56, so that water flows so
long as a user stands near the antenna.
FIG. 2 shows a different embodiment of the invention, the same
reference numerals and symbols as used in FIG. 1 denoting
corresponding parts. In FIG. 1, to render the compensating circuit
32 operative again a predetermined period of time after the urinal
was initially flushed, the base voltage of the transistor Tr5 is
reduced to the ground potential, thereby deenergizing the relay RY
so that the contact S1 is closed again. In FIG. 2, to accomplish
the same result, the terminal voltage of the condenser C4 is
applied through a Zener diode ZD to the base of the transistor Tr8
which is connected across the condenser C2 by a line L4. Just as in
the case of FIG. 1, when the delay time provided by the timer 38 is
over, the transistor Tr8 becomes conductive, whereupon the
condenser C2 discharges through the conducting transistor Tr8, so
that the capacity of the diode CV increases, thereby increasing the
voltage level at the terminal a of the detecting circuit 10 as if
there were nothing present in the field of the antenna 12. As a
result, the relay RY is deenergized to restore the original
condition of the system.
In FIG. 1, the signal So is taken out from the collector of the
transistor Tr4, while in FIG. 2 it is taken out from the collector
of the transistor Tr5. In the latter case, the circuit connection
is such that the collector output of the transistor Tr5 is
controlled by the timer including the condenser C3. Therefore, such
an on-off delay timer as shown at 44 in FIG. 1 can be dispensed
with in FIG. 2 if a similar valve control circuit is to be
connected to the line L3.
In FIGS. 1 and 2, the signal So is taken out of the collectors of
the transistors Tr4 and Tr5, respectively. Alternatively, the line
L3 may be removed and, instead, the relay RY may be additionally
provided with a normally closed contact S4 and a normally open
contact S5 as shown in FIG. 3 so that a signal produced upon
operation of the contact S4 may be used as the control signal So in
the following manner: FIG. 3 may be combined with either FIG. 1 or
FIG. 2, the line L3 and also the blocks in FIG. 1 being removed
therefrom. When a person enters the field of the antenna 12, the
relay RY is energized so that the contact S4 is opened and the
contact S5, closed to complete a discharge path for the condenser
of a differentiator 62. When the person has gone out of the antenna
field, the relay RY is deenergized so that the contact S5 is again
opened and the contact S4, again closed, whereupon the
differentiator 62 produces an output pulse, which triggers a
monostable multivibrator 63 to produce an output of a predetermined
pulse width. This pulse is amplified by an amplifier 64 and
energizes a solenoid 65 for opening a valve. It will be seen that
in FIG. 3, the urinal is flushed only after it has been used.
* * * * *