Motor timing automatic reversing operation controller

The circuit shown in the attached figure can be used for the automatic reversing operation circuit of the washing machine or the fan motor that needs to inhale/exhaust air. The dotted frame in the figure is the electrical schematic diagram of the motor M. C is a split-phase capacitor, which is used to generate a rotating magnetic field to rotate M. L1 and L2 are windings with exactly the same parameters and can be the main and auxiliary windings of each other. The contact connection of the relay K is used to change the rotation direction of M.

　　After the power switch S is turned on, M is energized and rotates forward, and the DC power supply (DC18V) charges the capacitor C3 through the potentiometer RP2 and the resistor R6, and the delay circuit composed of the single junction transistor V3 starts timing. When the voltage on C3 reaches the peak voltage of V3. V3 is turned on, and a pulse voltage is generated on the resistor R5 and applied to the G and K poles of the thyristor V2. V2 is triggered to turn on, and the relay K is energized and pulled in, and the wiring of M is changed and reversed. At this time, the normally open contact K-1 of K is closed to short-circuit C3, so that the delay circuit composed of V3 stops timing. At the same time, because the forward voltage drop of V2 is very small (about 0.3V) when it is turned on, the potential of point A is close to 0V, and another delay circuit composed of the single junction transistor V1 is turned on, and the DC power supply (DC18V) charges the capacitor C1 through the potentiometer RP1 and the resistor R1. When the voltage on C1 reaches the peak voltage of V1, a pulse voltage is generated on the resistor R3 and added to the A and K poles of V2, causing V2 to be turned off, K to lose power and release, and M to restore the connection and resume forward rotation. After that, the circuit cycles the above process to achieve automatic timing reversal of M.

　　V2 uses a plastic-encapsulated small unidirectional thyristor (BT151 type 1A/400V), C1 and C3 use tantalum electrolytic capacitors. Adjusting the resistance of RP1 and RP2 can change the forward and reverse time of M respectively (up to about 12 minutes). If you want to extend the forward and reverse time, you can increase the resistance of RP1 and RP2 or increase the capacity of C1 and C3 according to actual needs.

　　Because the forward and reverse time of M can be adjusted independently and do not affect each other, it is very convenient to adjust and use.