U.S. patent application number 09/728208 was filed with the patent office on 2001-06-14 for electronically commutated dc motor.
Invention is credited to Lukenich, Stefan, Schmider, Fritz.
Application Number | 20010003412 09/728208 |
Document ID | / |
Family ID | 8082399 |
Filed Date | 2001-06-14 |
United States Patent
Application |
20010003412 |
Kind Code |
A1 |
Schmider, Fritz ; et
al. |
June 14, 2001 |
Electronically commutated DC motor
Abstract
An electronically commutated motor (4) has a stator (14) with
two winding phases (25, 26) which are alternatingly supplied with
current during one rotor rotation through 360.degree. cl. The motor
also has a permanent-magnet rotor (28) which, when the motor (4) is
currentless, assumes at least one predefined rotational position
from which the rotor starts in a desired rotation direction upon
excitation of a predefined winding phase. A bistable multivibrator
(64), which is controlled by the voltage that is induced by the
rotor in the instantaneously currentless winding phase, is provided
for alternatingly switching on the two winding phases. The bistable
multivibrator (64) has an electrical preferred position (92) that
it assumes when the motor (4) is switched on, in order to supply
power, during the switching-on operation, to the predefined winding
phase and thereby to allow the rotor to start in the desired
rotation direction. The motor current can be temporarily increased
at startup in order to increase the torque at startup.
Inventors: |
Schmider, Fritz; (Hornberg,
DE) ; Lukenich, Stefan; (Singen, DE) |
Correspondence
Address: |
WARE FRESSOLA VAN DER SLUYS &
ADOLPHSON, LLP
BRADFORD GREEN BUILDING 5
755 MAIN STREET, P O BOX 224
MONROE
CT
06468
US
|
Family ID: |
8082399 |
Appl. No.: |
09/728208 |
Filed: |
November 30, 2000 |
Current U.S.
Class: |
318/400.11 |
Current CPC
Class: |
H02P 6/22 20130101; H02K
5/225 20130101 |
Class at
Publication: |
318/254 |
International
Class: |
H02K 023/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 1, 1999 |
DE |
299 21 161.4 |
Claims
What is claimed is:
1. An electronically commutated motor (4) comprising: a stator (14)
that has two winding phases (25, 26), of which, during one rotor
rotation of 360.degree. cl., firstly current is delivered to the
one winding phase (25) within a first rotation angle ranger via an
associated first semiconductor switch (56), and within a subsequent
second rotation angle range, current is delivered to the other
winding phase (26) via an associated second semiconductor switch
(62); a permanent-magnet rotor (28) which, when the motor (4) is
currentless, assumes at least one predefined rotational position,
from which the rotor (28) starts in a desired rotation direction
upon excitation of a predefined winding phase; a commutation
apparatus for alternatingly switching on the first semiconductor
switch (56) or the second semiconductor switch (62), said
commutation apparatus comprising a bistable multivibrator (64)
whose switching state is controlled by the voltages that are
induced, respectively, by the permanent-magnet rotor (28) in that
winding phase (25 or 26) which is currentless at that instant and
which, in the instantaneous rotation angle range of the rotor (28),
in not being supplied with current via its associated semiconductor
switch (56 or 62); the bistable multivibrator (64) having an
electrical preferred position (92) that it assumes when the motor
(4) is switched on, in order to supply power, during the
switching-on operation, to the predefined winding phase.
2. The motor according to claim 1, wherein the voltage induced in
the currentless winding phase is transformed via a pulse-shaper
stage (80, 86) into a switching pulse (76, 78) for switching over
the bistable multivibrator (64).
3. The motor according to claim 1, further comprising a current
regulator (58) which regulates the current (I) through the winding
phases (25, 26) to a predefined value.
4. The motor according to claim 3, further comprising an
arrangement (94) which deactivates the current regulator (58)
during a predefined time period after the motor (4) is switched on,
in order to allow an increased starting current.
5. The motor according to claim 4, wherein the arrangement (94) has
a switching member (132) which is switched on during a predefined
time period after the motor (4) is switched on and, in that
context, bypasses the current regulator (58) in order to allow an
increased starting current through the predefined winding
phase.
6. The motor according to claim 3, wherein the semiconductor
switches are configured as power transistors (56, 62); and each
power transistor has, associated with it, a transistor (120, 124)
which becomes more conductive as the motor current (I) increases
and thus reduces the base current of the power transistor (56, 62)
associated with it, so as thereby to keep the motor current (I)
substantially constant during operation.
7. The motor according to claim 3, wherein the current (I) through
the winding phases (25 or 26) is regulated to a substantially
constant value when the motor is running.
8. The motor according to claim 1, wherein there is provided, for
each winding phase (25, 26), a diode (82, 88) which is polarized in
such a way that it decouples the induced voltage from that winding
phase which, in the instantaneous rotation angle range of the rotor
(28), is not being supplied with current via its associated
semiconductor switch (56 or 62).
9. The motor according to claim 8, wherein the decoupled induced
voltage (FIG. 5) is transformed into a substantially square-wave
signal; and the switchover of the bistable multivibrator (64) is
controlled by an edge of that signal.
10. The motor according to claim 1, wherein a terminal (S) is
provided at which, when the motor is rotating, a signal (194) can
be picked off, whose frequency is determined by a voltage that is
induced by the permanent-magnet rotor (28) in a currentless winding
phase (25 or 26) that, in the instantaneous rotation angle range of
the rotor (28), is not being supplied with power via its associated
semiconductor switch (56 or 62).
11. The motor according to claim 1, wherein the bistable
multivibrator (64) is brought into an electrical preferred position
by way of the switching-on operation of the motor (4).
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to an electronically
commutated direct-current motor (ECM).
BACKGROUND
[0002] Motors of this kind are used, inter alia, to drive miniature
fans (cf. EP-A1-0 908 630 and corresponding U.S. Pat. No.
6,013,966, FEHRENBACHER et al). For various reasons, it may be
desirable to operate such a motor without a Hall generator, and for
that purpose to commutate it with the voltage that is induced,
during operation, by the rotor in the stator winding. This is
known, for example, from U.S. Pat. No. 4,156,168. VOGEL, but in the
case of this known motor the direction in which it will start after
being switched on is not certain, and this known motor is therefore
suitable only for specific applications in which rotation direction
is not important.
SUMMARY OF THE INVENTION
[0003] One object or the invention is therefore to provide new
electronically commutated motor whose startup rotation direction is
certain. In accordance with the invention, the motor used is one
having a rotor that, when the motor is currentless, has at least
one mechanical preferred position. The current in the motor is
controlled using a bistable multivibrator that has, at startup, an
electrical preferred position which is adapted to the mechanical
preferred position of the rotor. At startup, the result of the
electrical preferred position is that the stator is excited in such
a way that the rotor starts, from its mechanical preferred
position, in the correct rotation direction. Because a separate
rotor position sensor is eliminated, a motor of this kind has a
simple configuration with good efficiency, since the power
consumption for a rotor position sensor is eliminated. The
invention is therefore particularly advantageous for miniature and
subminiature motors in which the power consumption of a rotor
position sensor, for example a Hall TC, would greatly reduce the
electrical efficiency; and it is highly suitable, for example, for
motors in which the electronic components are arranged separately
from the actual motor (i.e. stator with stator winding, and
rotor).
[0004] Further details and advantageous developments of the
invention are evident from the exemplary embodiment described below
and shown in the drawings, which is in no way to be understood as a
limitation of the invention.
BRIEF FIGURE DESCRIPTION
[0005] FIG. 1 is a longitudinal section through a fan 1 that is
driven by an electronically commutated motor 4;
[0006] FIG. 2 is a plan view at the fan of FIG. 1, viewed in the
direction of arrow II of FIG. 1;
[0007] FIG. 3 is a schematic circuit diagram of a motor according
to the present invention;
[0008] FIG. 4 shows a preferred exemplary embodiment of a circuit
corresponding to FIG. 3, with further details:
[0009] FIG. 5 is a graph of the voltage that occurs during
operation at winding phase 25 of FIG. 4, i.e. between points 3A and
3B;
[0010] FIG. 6 is a graph of the total current T for the arrangement
shown in FIG. 4;
[0011] FIG. 7 is a graph of the voltage at an output S of the
circuit of FIG. 4 when the motor is rotating; and
[0012] FIG. 8 is a graph of the voltage at output S of FIG. 4 when
rotor 6 is jammed or blocked from rotating.
DETAILED DESCRIPTION
[0013] FIGS. 1 and 2 show, purely by way of example, a radial fan 1
as known from U.S. Pat. No. 6,013,966. This has a fan wheel 2 and
an electronically commutated external-rotor claw polo motor 4 which
directly drives fan wheel 2. Motor 4 has a permanent magnet
external rotor 6. As shown in FIG. 2, two diametrically opposite
positioning magnets 8 are provided, when motor 4 is at a
standstill, these rotate rotor 6 into a preferred position (also
called the "starting position") from which it can easily start up.
Magnets 8 are arranged in pocket 12 of fan housing 10.
[0014] Motor 4 has a stator 14 with two opposing claw-pole pieces
18, 19 between which, as shown, is located an annular winding 16 on
a winding body 15. Winding 16 is wound in bifilar fashion and has
two winding phases 25 and 26 which are also shown in FIGS. 3 and 4.
Phase 25 has two terminals 3A and 3B which are shown in FIGS. 2, 3,
and 4, and phase 26 has two terminals 3C and 3D.
[0015] Claw-pole pieces 18, 19 have claw poles 20 which extend in
an axial direction (cf. FIG. 1). The rotor magnet is labeled 28,
and can be a so-called "rubber magnet," i.e. a mixture of rubber
and hard ferrite. It is located in a support piece 29 that is
configured integrally with fan wheel 2 and in which a shaft 30 is
also mounted. The latter runs in a radial plain bearing 32, and its
free end is axially braced against a thrust bearing 34. Rotor 6 is
axially offset with respect to stator 14 in order to generate a
force F directed toward bearing 34.
[0016] Fan wheel 2 has radially extending fan blades 36. An axial
air intake opening is labeled 38. Located in it is an NTC (Negative
Temperature Coefficient) resistor 40 that serves an a temperature
sensor and is connected to two terminals K1 and K6 (FIG. 2).
[0017] Terminals K1, K6, and 3A through 3D extend axially downward
in the form of elongated pine 44 whose lower ends 46 can be
soldered, as shown at 49, onto a circuit board 47 indicated with
dot-dash lines. Mounts 48 for attaching fan 1 are also provided.
With these mounts, the fan can ba attached, for example, to circuit
board 47.
[0018] Fans of this kind are particularly suitable for use as
so-called "circuit board fans," i.e. for direct placement on a
circuit board in order to cool components present thereon.
Reference is made to U.S. Pat. No. 6,013,966 for further
details.
[0019] The electronic components B for operation of such a fan are
often mounted by the customer on his own circuit board 47, as
symbolically indicated in FIG. 1, and the customer purchases only a
"naked" fan 1 and installs it on his circuit board, so that an
operable motor is created only by such installation. This kind of
"motor manufacture" generally makes it impossible to use rotor
position sensors, for example a Hall generator, which is otherwise
often used in electronically commutated motors to control
commutation.
[0020] Since rotor magnet 28 is located, because of the effect of
stationary magnets 8, in a predefined starting position or in one
of a plurality of predefined starting positions when the motor
starts, a predefined winding phase of stator winding 16 must
receive a starting current in a predefined direction upon switching
on. The circuit shown in FIGS. 3 and 4 serves to switch on this
starting current. As a result of this starting current, rotor
magnet 28 is caused to rotate in the desired direction and thereby
induces voltages in the two winding phases 25 and 26; these
voltages, after suitable pulse shaping, cause commutation of the
current through the two winding phases 25 and 26. This is also
known in the art as "commutation with the induced voltage."
[0021] Instead of the motor defined in U.S. Pat. No. 6,013,966, it
is of course possible to use in the same fashion, for example, a
motor as defined in German Utility Model DE U1 295,7 or in German
Utility Model DE-U1 8 702 271.0. FIGS. 1 and 2 thus represent only
a preferred exemplary embodiment whose purpose is to allow a better
comprehension of the invention since, without such an example, the
invention might possibly be difficult to understand.
[0022] FIG. 3 is an overview circuit diagram to explain basic
functions of the present invention.
[0023] As show in FIG. 3, winding phase 25 is connected at its
terminal 3A to a positive line 52 that can be connected via a
switch 54 to a voltage source (not shown), usually to the battery
of a vehicle with a voltage between 8 and 16 V. The other terminal
3B of winding phase 25 is connected to a first semiconductor switch
56 that in turn is connected via a node 57 and a current regulator
58 to a negative line 60 (ground).
[0024] Second winding phase 26 is connected at its terminal 3C to
positive line 52, and its terminal 3D is connected via a second
semiconductor switch 62 to node 57.
[0025] Semiconductor switches 56, 62 are controlled via a bistable
flip-flop 64, which during operation generates first square-wave
commutation signals 66 which are fed via a delay circuit 68 to
first semiconductor switch 56, and second square-wave commutation
signals 70 which are opposite in phase to first square-wave
commutation signals 66 and are fed via a delay circuit 72 to second
semiconductor switch 62.
[0026] The function of delay circuits 68, 72 is to delay the
switching on and off of semiconductor switches 56 and 62,
respectively, and to make those operations less abrupt, so that
motor 4 runs particularly quietly.
[0027] Pulses 76, 78 serve to reverse flip-flop 64. Pulses 76 are
generated by an arrangement 80 which has conveyed to it, via a
diode 82, the so-called "induced voltages" or "counter-EMF" that is
induced by rotor magnet 28 in the currentless winding phase 25.
Thin voltage is converted in arrangement 80 into a square-wave
signal, and its edges are differentiated by a capacitor 84 and
generate the pulses 76 which commutate flip flop 64 into the one
direction.
[0028] Pulses 78, which are offset in time with respect to pulses
76, are generated by an arrangement 86 which has applied to it, via
a diode 88, the voltage that is induced by rotor magnet 26 in the
currentless winding phase 26. That voltage is converted in
arrangement 86 into a square-wave signal, and its edges are
differentiated by a capacitor 90 and generate pulses 70 which
commutate flip-flop 64 into the other direction.
[0029] For starting, flip-flop 64 acquires a specific electrical
position due to a starting apparatus 92.
[0030] Since the operating voltage in a motor vehicle can be, for
example, between 8 and 16 V, current regulator 58 regulates motor
current I (FIG. 3) to a predefined value that corresponds, for
example for a specific fan 1, to a rotation speed of 2800 RPM.
Directly after switch 54 switches on, current regulator 58 is
deactivated by a timer 94 for a predefined time period so that
motor 4 can start up with its maximum performance.
[0031] Mode of_operation (FIG. 3)
[0032] At startup, constant-current regulator 58 is deactivated by
timer 94 for a predefined time. e.g. for 0.5 second, so that motor
4 can start at maximum current. At the same time, switching member
92 brings flip-flop 64 into a suitable electrical position so that,
for example, first semiconductor switch 56 is switched on and first
winding phase 25 receives current, with the result that rotor
magnet 28 begins to rotate at high acceleration in the desired
rotation direction.
[0033] During that rotation, an alternating voltage is induced by
rotor magnet 28 in each of winding phases 25 and 26 (cf FIG. 5).
The positive part of the alternating voltage in winding phase 25 is
fed via diode 82 to arrangement 80, and the positive part of the
alternating voltage in winding phase 26 is fed via diode 88 to
arrangement 86.
[0034] In arrangements 80, 86, the relevant voltages are converted
into square-wave signals, and the latter are differentiated by
capacitors 84 and 90, respectively, thereby creating pulses 76 and
78, respectively, which switch flip-flop 64 between its bistable
positions.
[0035] The result is to create pulse sequences 68, 70 which, as
rotor magnet 28 rotates, effect commutation of motor 4, i.e. the
switching on and off of semiconductor switches 56 and 62,
respectively.
[0036] When motor 4 begins to reach its operating speed current
regulator 58 is activated by timer 94 and controls current I to a
predefined value that is independent of the operating voltage. In a
motor vehicle, the latter can vary at ratio of 1:2. In the case of
a defined load, e.g. when a fan is being driven, current I
represents an indirect indication of the rotation speed, in other
words, if current is controlled to a predefined value, then the
rotation speed is thereby kept at a predefined value.
[0037] FIG. 4 shows a preferred exemplary embodiment of the
invention. Identical or functionally identical parts are labeled
with the same reference characters as in the preceding figures, and
usually are not described again.
[0038] Bistable flip flop 64 contains two npn transistors 100, 102
whose emitters are connected to negative line 60 and whose
collectors are connected via respective resistors 104 and 106 to
positive line 52. The base of transistor 100 is connected via a
resistor 108 to the collector of transistor 102, and the base of
transistor 102 is connected via a resistor 110 to the collector of
transistor 100.
[0039] If transistor 100 is conductive, the base of transistor 102
has a low potential and that transistor is blocked, so that
transistor 100 receives a base current via resistor 108. Because of
the symmetry of the circuit, the converse is equally true,
Flip-flop 64 thus has two stable states, and it can be switched
back and forth between those stable states by way of electrical
pulses. This switching back and forth occurs at the time of each
zero crossing of the negative edges of the induced voltage.
[0040] When transistor 100 is conductive, the base of npn
transistor 62 (which serves as the second semiconductor switch)
acquires a low potential via a resistor 112, and that transistor is
blocked. Transistor 102 is inhibited, and npn transistor 56, which
serves as the first semiconductor switch, therefore acquires--via
resistor 106 and a resistor 114--a positive potential at its base
and becomes conductive, so that a current flows through winding
phase 25. That current I is regulated by current regulator 58 to an
approximately constant value (cf. FIG. 6).
[0041] Current I flows through a shared emitter resistor 116 of
transistors 56 and 62, and voltage U at that resistor 116 is fed
via a resistor 118 to the base of an npn transistor 120, and via a
resistor 122 to the base or an npn transistor 124. The collector of
transistor 120 is connected to the base of transistor 56, and the
collector or transistor 124 to the base of transistor 62. The
emitters of transistors 120, 124 are connected to negative line
60.
[0042] When current I rises, transistors 120 and 124 become more
conductive, so that the base current of transistor 56 or 62 that is
conductive at that instant is correspondingly reduced, bringing
about a decrease in current I. The latter is thereby kept at a
constant value (cf. the oscillogram in FIG. 6).
[0043] Each at transistors 56, 62 is equipped with a so-called
Miller capacitor 126, 128 between its collector and its base.
Coacting with base resistors 114 and 112, respectively, these
capacitors effect a delay in the rise and fall of current in the
transistor in question, and thus make motor 4 run particularly
quietly. Miller capacitors 126, 128 and resistors 112, 114 thus
represent an embodiment of delay circuits 68, 72 of FIG. 3.
[0044] The purpose of timer 94 is to deactivate current regulator
58, for a period of, for example, 0.5 seconds after motor 4 is
switched on, by bypassing current controller 58 via an npn
transistor 132.
[0045] Transistor 132 is controlled by a pnp transistor 136 whose
collector is connected via a resistor 134 to the base of transistor
132, whose emitter is connected to positive line 52, and whose base
is connected via a resistor 140 to a node 142 that is connected via
a resistor 144 to positive line 52 and via a capacitor 146 to
negative line 60.
[0046] Capacitor 146 is discharged when motor 4 is switched on, so
that transistor 136 has a negative base potential and conducts.
Transistor 132 thereby receives a base current and is also
conductive, so that it bypasses current regulator 58.
[0047] Capacitor 146 then charges through resistor 144, with the
result that, after about 0.5 second, the two transistors 136 and
132 are inhibited, so that current regulator 58 is activated. At
this point in time, motor 4 has usually reached its operating
speed.
[0048] Diode 82 is connected at its anode to terminal 3B of first
winding phase 25, and at its cathode to the emitter of a pnp
transistor 150 whose base is connected to a node 152 and whose
collector is connected via a resistor 154 to negative line 60 end
via a resistor 156 to the base of an npn transistor 158, whose
emitter is connected to negative line 60 and whose collector is
connected via a resistor 160 to positive line 52 and, via capacitor
84 (cf. FIG. 3), to the base of transistor 100.
[0049] Node 152 is connected via series circuit 164 of two diodes
(e.g. BAV99) to positive line 52, and via a resistor 166 (e.g. 51
k.OMEGA.) to negative line 60. Node 152 thus has a potential that
is more negative, by an amount equal to a substantially constant
voltage, than the potential of positive line 52. Transistors 150,
170 are thereby brought to their switching threshold, so that
transistor 150 senses the temporally later zero crossing (at
approximately 200 in FIG. 5) of the positive voltage induced in
winding 25, and transistor 170 senses the temporally later zero
crossing of the positive voltage which is induced in winding
26.
[0050] Diode 88 is connected at its anode to terminal 3D) of second
winding phase 26, and at its cathode to the emitter of a pnp
transistor 170 whose base is connected to node 152 and whose
collector is connected via a resistor 172 to negative line 60 and
via a resistor 174 to the base of an npn transistor 176 whose
emitter is connected to negative line 60 and whose collector is
connected via a resistor 178 to positive line 52 and via capacitor
90 (cf. FIG. 3) to the base of transistor 102.
[0051] When transistor 56 is conductive, point 3B has a low
potential and diode 82 is blocked. When transistor 56 is inhibited
by commutation, winding 25 is currentless and rotor 19 induces in
winding 25 a positive voltage half-wave 202 (FIG. 5) that is more
positive than the potential at node 152, so that diode 82 becomes
conductive and transistor 150 receives a base current, also becomes
conductive, and in turn makes transistor 158 conductive, so that by
way of capacitor 84, transistor 100 of flip-flop 64 is kept
blocked, and by way of resistor 112, transistor 62 receives a base
current and allows a current to flow through second winding phase
26.
[0052] After a rotor rotation of approximately 180.degree. el., the
potential at point 3B drops below the potential at node 152, so
that diode 82, transistor 150, and transistor 158 are inhibited,
i.e the voltage at the collector of transistor 158 suddenly becomes
more positive, and capacitor 84 transfers that change in potential
to the base of transistor 100 in flip-flop 64, so that transistor
100 becomes conductive and consequently, via transistor 110,
transistor 102 is inhibited.
[0053] The switchover of flip-flop 64 is thus brought about by the
trailing edge (labeled 200 in FIG. 5) of positive portion 202 of
the voltage the induced voltage U.sub.3A-3B, which causes flip-flop
64 to switch over approximately at its zero crossing, (Rising edge
201 in FIG. 5 occurs directly after a switchover of flip-flop 64,
when the corresponding output-stage transistor 56 is
inhibited.)
[0054] When motor 4 is switched on, the different values of
capacitors 84 (e.g. 6.8 nF) and 90 (e.g. 3.3 nF) mean that
transistor 100 becomes conductive, so that at startup, winding
phase 25 is always the first to receive current via its transistor
56, and motor 4 thus starts in the correct rotation direction from
its starting position that is brought about by magnets 8 in FIG. 2.
Flip-flop 64 thus, when switching on occurs, acquires an electrical
preferred position which is correctly associated with the starting
position of rotor magnet 28.
[0055] Since transistor 100 has become conductive as a result of
this switchover pulse, transistor 62 is inhibited via resistor 112,
and conversely transistor 56 is switched on via resistor 114
because transistor 102 is inhibited, so that winding phase 25 now
receives current.
[0056] The switching on of transistor 56 is delayed by resistor 114
and capacitor 126, and the switching off of transistor 62 is
similarly delayed by resistor 112 and capacitor 128, so that
despite the abrupt switchover of flip-flop 64, the switching
operations proceed smoothly and no unpleasant motor noise is
created by rapid switching operations.
[0057] Because of the symmetry of the circuit, commutation in the
opposite direction, i.e. from transistor 56 (becomes inhibited) to
transistor 62 (becomes conductive) does not need to be describe,
since the operations occur as the inverse of the operations just
described.
[0058] The positive induced voltage in a currentless winding phase
25 or 26 is thus converted by the above-described circuit into a
square-wave signal, and the edge at the end of that square wave
causes a switchover pulse for flip-flop 64 which causes the
previously currentless transistor (56 or 62) to be switched on and
the previously conductive transistor (62 or 56) to be switched off.
This results in secure and reliable commutation by way of the
induced voltage, smooth and low-noise commutation being achieved
due to the above-described delay circuit elements, despite the
abrupt switchover of flip-flop 64.
[0059] An external terminal S is connected via a resistor 190 to
the collector of transistor 150. The signal at that collector,
shown in FIGS. 7 and 8, indicates whether motor 4 is rotating or is
jammed or blocked. If motor 4 is rotating, pulses 194 are obtained
at terminal S at a frequency that is proportional to the motor
rotation speed. This slate is shown in FIG. 7. If the motor is
jammed, what is received at output S are pulses 196 at a very high
frequency, or alternatively a zero frequency. The state with the
high frequency is shown in FIG. 8. This makes it easy to monitor
whether motor 4 is running or is jammed.
[0060] Preferred values of the components in FIG. 4
1 Motor: Operating voltage 8 to 16 V Power consumption 0.5 W
Rotation speed 2800 RPM Transistors 56, 62 BC817/40 Transistors
136, 150, 170 1/2 BC857BS Other transistors 1/2 BC847BS Diodes 164
BAV99 Diodes 82, 88 BAS216 Capacitors 126, 128 4'/ nF Capacitor 84
6.8 nF Capacitor 90 3.3 nF Capacitor 146 220 nF Resistors 104, 106,
118, 122, 134, 154, 172 10 k.OMEGA. Resistors 108, 110, 156, 160,
174, 178, 190 100 k.OMEGA. Resistors 112, 114 15 k.OMEGA. Resistor
166 51 k.OMEGA. Resistor 116 39 .OMEGA. Resistors 140, 144 1
M.OMEGA.
[0061] Many variants and modifications are of course possible
within the scope of the present invention. Therefore, the invention
is not limited to the particular embodiments shown and described,
but rather is defined by the following claims.
* * * * *