JPH01157221A - Automatic stopping circuit for dc motor - Google Patents

Abstract

PURPOSE:To prevent a motor from burning, by contriving the output of a rotation detecting transistor connected to the terminal of the DC motor, to be turned OFF when the rotation of the DC motor is constrained, and by turning OFF a motor driving transistor. CONSTITUTION:When a resistor R1, a transistor(Tr)Q1, and a resistor R2 are connected to the terminals T1, T2 of a DC motor M and the motor M is rotated forward by an external force, then an induced electromotive force(En) is generated. When the electromotive force exceeds the base/emitter forward-voltage of the TrQ1, then base current flows to the TrQ1, and the TrQ1 is turned ON, and a TrQ2 is also turned ON, and the forward rotation is continuously kept. When the rotation of the motor M is constrained due to any reason in this state, then negative pulse is generated from the motor M, and the TrQ1 is turned OFF, and the TrQ2 is also turned OFF. In this case, when a speed is lowered to a rotational speed approximate to stop, then the electromotive force En is also set to be extremely less, and the TrQ1 is turned ON no longer. As a result, the motor M is automatically stopped, and is prevented from burning. A device is adequate for radio control.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an automatic stop circuit for a DC motor.

[Summary of the invention]

A rotation detection transistor is connected to the terminal of the DC motor and turned on by an induced electromotive force, and momentarily turned off by a pulse generated in the armature winding of the DC motor, and the output current of this rotation detection transistor becomes a control current. A drive transistor is provided which turns on when the rotation detection transistor is turned on and supplies a drive voltage to the DC motor to cut off the power supply when the motor is restrained, and a drive transistor is provided between the rotation detection transistor and the drive transistor. , an automatic stop circuit for a DC motor that can cut off the power supply when the voltage decreases with a simple configuration by adding a Zener diode that cuts off the control current when the power supply voltage drops below a predetermined value. It is.

[Conventional technology]

For example, in an electric radio controlled airplane -
Once the propeller is rotated, the drive voltage supplied to the DC motor for rotating the propeller will not be cut off unless the switch is turned off. For this reason, if the propeller is restrained due to a collision or crash during flight, more restraint current than necessary flows through the propeller rotating motor, which is not economical, and also places an unreasonable load on the motor and other mechanisms. This may shorten the life of the electric radio-controlled airplane, or there is a risk of fire due to the heat generated by the DC motor or battery. Furthermore, if the battery consumes too much electrical energy during flight, the servo motors for flight control will no longer be able to be driven, making it impossible to land the radio-controlled airplane.

Conventional automatic shutdown circuits have used fuses to ensure that power is cut off when the motor is tied up. In addition, a magnetic relay is installed in the circuit that supplies the power supply voltage to the motor, and its reduced voltage recovery characteristic is utilized to cut off the power supply to the motor when the power supply voltage drops below this voltage.

[Problem that the invention seeks to solve]

When a fuse is used to detect a motor being locked, the supply voltage is cut off by blowing out the fuse due to the locking current. Therefore, not only is the electrical energy of the battery wasted when the vehicle is restrained, but also the fuse must be replaced each time a restraint is detected. Further, if the restraint current does not reach the rated current of the fuse, the power supply to the DC motor cannot be cut off.

Furthermore, the magnetic relays used to cut off the power supply to the motors when the power supply voltage drops are heavy, which has been an obstacle in reducing the weight of radio-controlled airplanes and the like.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention aims to provide a function of cutting off the power supply during locking and voltage reduction with a simple circuit configuration without using fuses or magnetic relays.

[Means for solving problems]

The automatic stop circuit for a DC motor of the present invention is connected to a terminal of the DC motor M and is turned on by an induced electromotive force, which is generated in the armature 1' wire at each polarity switching point of the commutator of the DC motor M. A rotation detection transistor Q1 which is turned off instantaneously by a pulse is connected so that the output current of the rotation detection transistor Q1 becomes a control current. A driving transistor Q2 that is turned on to supply a driving voltage to the terminal, a control electrode of the driving transistor Q2, and the rotation detection transistor Q.
1, and a Zener diode DI that cuts off the control current of the drive transistor Q2 when the applied reverse voltage drops below a predetermined voltage.

[For production]

Every time the rotation detection transistor Ql turns off momentarily, an induced electromotive voltage accompanying the rotation of the motor M is detected, and this induced electromotive force turns the rotation detection transistor Ql on again. When the electric motor M is restrained, the induced electromotive voltage becomes extremely small just before stopping, and once the detection transistor Q1 is turned off, it cannot be turned on again. Further, when the reverse voltage applied to the Zener diode DI becomes equal to or less than the Zener voltage due to a decrease in the power supply voltage, the control current stops flowing, so the driving transistor is turned off and power supply to the DC motor M is stopped.

〔Example〕

FIG. 1 shows an automatic stop circuit for a DC motor according to an embodiment of the present invention. This automatic stop circuit is built into, for example, a toy electric radio-controlled airplane, and the electric motor M is a well-known DC three-pole (phase) type commutator electric motor (Micromorph).

The emitter collector of a driving transistor Q2 that supplies a power supply voltage E is connected in series to a terminal T1 of the motor M, and a Zener diode D1 is connected to the base of this transistor Q2.

One end of the Zener diode D1 is connected to the base of Q2 in a direction in which the power supply voltage E is applied as a reverse voltage, and the collector emitter of the rotation detection transistor Q1 is connected in series to the other end. The base of this detection transistor Q1 is connected to the terminal T of the motor M via a resistor R1.
1, and its emitter is connected to a terminal T2 (ground potential) of the motor M via a resistor R2.

Therefore, the emitter base of the transistor Q2, the Zener diode D1, the collector emitter of the transistor Q1, and the resistor R2 are connected in series, and when the switch S1 is closed, the power supply voltage E is applied to this series circuit.

These transistors QISQ2 are connected so that they are self-maintained in the on state. That is, once Q1 is turned on, its collector current becomes the base current of Q2, and Q2
turns on. Therefore, the collector voltage of Q2 increases and the driving voltage is supplied to the motor M. At this time, the base current is supplied from the collector of Q2 to Ql via the resistor R1, so that Ql is maintained in the on state.

The automatic shutdown circuit of the motor of FIG. 1 is kept off in the stationary state. Here, the motor M is rotated by an external force so that a positive voltage is generated at the terminal Tl of the motor M and a negative voltage is generated at the terminal T2 (this direction is referred to as normal rotation). Induced electromotive force En
is proportional to the rotational speed N of the armature.

E,1=AN (A is a constant) When E,l exceeds the base-emitter forward voltage ■□ of transistor Q1, a base current flows through resistors R1 and R2, and Ql turns on. Therefore transistor Q2
is also turned on, and forward rotation continues.

After starting the electric motor M in this manner, if the electric motor M is stopped due to, for example, an electric airplane crashing and the propeller being restrained, the automatic stop circuit shown in Fig. 1 will automatically stop according to the following principle. will be turned off.

Figure 2a %C shows the armature circuit of the motor M in Figure 1, and in this example, three-phase delta windings L+, Lg, and L3 are used.
a pole commutator C,, cg, C3 and a pair of brushes B+,
Consists of Bg. In the rotation position (a), 7” Rise B+
, Bz, and (7) the series is in parallel with the winding L1. In the rotational position (b), winding 2 is short-circuited, and winding 2, L, are parallel to each other, and in the rotational position (C), winding 1, 2 and 2 are short-circuited.

The winding L2 is connected in series with the winding L2. Therefore (b)
At the rotational position, a steep positive and negative pulse voltage is generated due to the reactance voltage between the terminals T1 and T2 of the motor M, as shown in the waveform diagram of FIG. Since a connection state similar to that shown in FIG. 2(b) occurs six times per rotation of the armature, this pulse voltage is generated every 60 degrees.

Therefore, in FIG. 1, for example, when the automatic stop circuit is on and the electric motor M is rotating in the normal direction, the terminals T1 and T
Since the base and emitter of the sensing transistor Q1 are reverse biased by the negative pulse generated between the two, these transistors are momentarily turned off every time the motor M rotates by 60 degrees. However, as long as the electric motor M is rotating, the automatic stop circuit is kept on by its positive induced electromotive voltage.

If the motor M is restrained by an external force, the restraint current generally tries to continue flowing, but immediately before the motor M is restrained, a negative pulse generated in the connection state shown in FIG. 2(b) turns off the transistor Q1. . At this point, when the rotational speed has decreased to a point close to stopping, the induced electromotive force E4 at terminals T1 and T2 has become extremely small, and E,%≦VOI, and the sensing transistor Q1 can no longer be turned on. .

The control circuit is therefore turned off.

Note that in the automatic stop circuit shown in Fig. 1, transistor Q1
The resistor R2 inserted into the emitter of Ql acts as a negative feedback for the collector current of Ql.

That is, when the base current of Ql increases and the collector current tends to increase, the emitter voltage increases, so the base current decreases. Therefore, the transistor Q1 can be operated in the active region, excess minority carriers in its base region can be eliminated, and the delay time at turn-off can be minimized.

Therefore, as the motor M rotates, the pulse generated in the armature winding at the commutator polarity switching point causes the transistor Q to
1 can be completely turned off instantly. Therefore, restraint detection is performed reliably.

Therefore, according to the automatic stop circuit shown in FIG. 1, when the electric motor M is restrained, turn-off does not fail, and restraint detection and power supply cutoff are reliably performed.

When the automatic stop circuit of the embodiment is applied to an electric radio-controlled airplane, if the propeller is rotated in the forward direction by an external force, the circuit will be turned on and the circuit will continue to rotate in the forward direction, and the propeller will be restrained due to a collision or crash during flight. The circuit turns off instantly. Therefore, there is no starting current or locking current (both larger than during flight) of the DC motor, so there is extremely little wastage of energy such as batteries, and there is no excessive load on the motor, mechanism, etc., so troubles can be avoided. It can also reduce and extend the lifespan of radio controlled airplanes.

In addition, because the circuit is simple, these functions can be easily obtained at low cost, and unlike fuses that are blown by overcurrent, there is no need to replace parts every time overcurrent flows, and the operation is easy. is certain. Also, since the electric motor only rotates in one direction, the circuit will not turn on even if the propeller is rotated in the opposite direction.

When the DC motor M is being driven, the terminal voltage (power supply voltage) E of the battery I gradually decreases. The voltage E of the battery 1 is also supplied to a receiving circuit that receives a remote control signal transmitted from a remote controller, and a flight control servo motor whose operation is controlled by this receiving circuit.

Therefore, if all the electrical energy of the battery 1 is consumed while driving the electric motor M, the receiving circuit and the flight control servo motor cannot be operated.

In order to eliminate such inconvenience, in this embodiment, as described above, the base-emitter of the driving transistor Q2,
The Zener diode D1, the collector emitter of the sensing transistor Q1, and the resistor R2 are connected in series, and the terminal voltage E of the battery -1 is applied to both ends of this series circuit. Therefore, the terminal voltage E decreases and becomes E S VDIIt + VDI + VCtl (Va
Es: Base-emitter forward voltage of Q2, Vm+
When the 7ener voltage of SDI reaches Vcit (collector-emitter saturation voltage of Ql), no current flows through the series circuit of Q2, DI, and Ql, so Q2 turns off and the drive voltage E supplied to the DC motor M becomes will be cut off.

The power supply voltage value when cutting off the power supply to DC motor M is
It can be changed by changing the Zener voltage V□ of the Zener diode DI. Therefore, by arranging a Zener diode D1 having an appropriate Zener voltage value in consideration of the discharge characteristics and final discharge voltage of the battery 1, the DC motor M It is possible to cut off the power supply to. This eliminates the need to mount a heavy magnetic relay on the airplane.
It is possible to secure electric power to drive the servo motors for controlling the altitude and direction of the airplane.

This automatic shutdown circuit can be used not only for radio-controlled airplanes, but also for various applications where the power supply to the DC motor is cut off when the DC motor is tied up or before the battery voltage drops to the final discharge voltage. When used in video tape recorders and video cameras, tape winding/
When the I return is completed and the DC motor is locked, the drive of the DC motor for tape running can be stopped when the battery voltage drops, and the tape wound around the rotating head can be transferred into the cassette. Electric power for rewinding, etc. can be secured.

If necessary, a start switch or a stop switch may be added to the control circuit shown in Figure 1.The start switch shorts the collector and emitter of the transistor Ql (or Q2) as shown by the broken line in Figure 1. It may be a bush switch s2.

The stop switch may be, for example, a bush switch that shorts the base and emitter of the transistor Q1 or Q2. By providing these start switches or stop switches, in addition to starting the electric motor M by external force and stopping it by restraint, it becomes possible to control start/stop using the switch. Alternatively, a switch may be provided to short-circuit both ends of the electric motor M to stop the control circuit.

[Effects of the Invention] As described above, the present invention provides an output of a rotation detection transistor that is connected to a terminal of a DC motor and is turned on by an induced electromotive force and instantaneously turned off by a pulse generated in the armature winding of the DC motor. between the electrode and a control electrode of a drive transistor that is turned on when the rotation detection transistor is turned on and supplies a drive voltage to the DC motor, with the output current of the rotation detection transistor serving as a control current; Since a Zener diode is provided that cuts off the drive current when the applied reverse voltage drops below a predetermined voltage, it is possible to detect reduced voltage and control power supply cutoff to the motor when the power supply voltage drops to a predetermined value. can be done with a single component Zener diode. Therefore, the configuration is simpler than the conventional system that utilizes the reduced voltage recovery characteristic of a magnetic relay, and the circuit can be made smaller and lighter.

In addition, since voltage drop detection and power supply cutoff control are performed at a minute current level for the control current of the transistor, voltage loss and power consumption are small, and operation is reliable. On the other hand, a Zener diode is provided in the control current path of the drive transistor, and the Zener diode is on when the power supply voltage is higher than a predetermined value, so when motor lock is detected by the rotation detection transistor, the Since the power supply is cut off, no binding failure occurs.

[Brief explanation of the drawing]

Fig. 1 is an automatic stop circuit diagram of a DC motor showing an embodiment of the present invention, Fig. 2 a''-c is an armature circuit diagram of the motor, and Fig. 3 is a terminal voltage waveform diagram of the motor. In the codes used for
−・−・・・−・・・−・Power supply voltage H−・・−
・・・・・−・−・・−Electric motor port 1−−１〜−−・−
1-----Transistor low for rotation detection 2------
・−・−・−Drive transistor R1, R2−・・−・
・-Resistance Ll"L3-・-1--Armature winding C, -C
,・−・−・−・・−・−Commutator B,,B,・・−−−
---11-Brush TI, T! '-1-...- terminal.

Claims (1)

[Claims] The motor is connected to a terminal of a DC motor and is turned on by an induced electromotive voltage, and is turned off instantaneously by a pulse generated in an armature winding at each polarity switching point of a commutator of the DC motor. A rotation detection transistor is connected so that the output current of the rotation detection transistor becomes a control current, and is turned on to supply a drive voltage to the terminal of the DC motor when the detection transistor is turned on. a driving transistor connected between a control electrode of the driving transistor and an output electrode of the rotation detection transistor, and controlling the driving transistor when an applied reverse voltage drops below a predetermined voltage; An automatic stop circuit for a DC motor that includes a Zener diode that cuts off current.