Bidirectional thyristor detection circuit diagram

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Bidirectional thyristor detection circuit

As shown in Figure NE555, R1, R2 and C1 constitute a pulse oscillator, the output pulse frequency is 1Hz, the duty cycle is approximately equal to o. 5 square wave pulse. After this pulse is output, the first path is applied to the anode of the triac via LED1, the second path is applied to the gate of the thyristor via R3 and SB, and the third path is applied to the base of VT1 and VT2 via R5. At this time, if SB is pressed, the pulse signal is applied to the gate of the thyristor through SB. If the triac is good, when the high level output of the pulse, VS will be forwarded and VT2 will be turned on. The pulse output by the power supply through the NE555 conversion passes through LED1 → R4 → VS → VT2 to form a path, and LED1 emits light. When the pulse is output low, VS will reverse the conduction, VT1 will also be turned on, and the current will form a path through the internal circuit of VT1 → VS → R4 → LED2 → NE555, and LED2 will emit light.