Who among motorists who have electroacoustical headlights, unknown unpleasant phenomenon, when the brush is frozen, and the engine starts (whether casually or when you turn on the windshield wiper when middle the headlights). Block contacts closed due to the backlash and deflection of the lever wiper, and the engine is stopped while the power is on. Destiny purifier headlights foregone conclusion: due to the large internal resistance staffing the fuse does not burn out until the complete combustion of the armature winding. Worth this engine is expensive, so from the convenience of usually refuse forever.
Fast double-such engines in their "Field", I have installed on their device (see figure). It has been more than 10 years, and the engines work.
When power is supplied to the motor for IC D1 is powered via parametric stabilizer R5VD2. The counter is reset the charge current of the capacitor C2. While at pin 5 of chip - low logic level, the transistor VT1 is closed, a VT2 is open. The engine starts to rotate. The counter counts the pulses of the clock generator with time-setting elements C1, R1, R2.
If interference to the rotation of the engine, flip the switch contacts S1 due to the overcharging of the capacitor C2, the counter is set back to the original condition, and the engine continues to rotate. If the locking contacts in within 10-15 seconds, do not switch, the counter is filled, and at its output there is a high logic level, which leads to the opening VT1. Transistor VT2 is closed. The motor is de-energized. In this state, the counter can to be a long time because of the diode VD1 picks up the vibrations when the filling.
The cycle of operation of the device is repeated at short-term relief (the shut-off of the dipped beam).
The transistor VT2 is running without a heatsink. VT1 - any low-power silicon with long leads for surface mounting. The entire device is mounted without price inside the motor housing on the mounting petals engine and trailer switch.
This is useful to collect for engines and cleaner windshield and rear Windows, although they fail due to freezing brushes relay due to the fact that the brushes are in front, and the driver manages to free them before burnout of the motor.
Author: V. M. Paley, Chernihiv