The following is a SCR fast tester circuit diagram.
Mainly composed of 555. The tester is composed of a pulse signal generator, a closed conduction loop, a light emitting diode, a thyristor SCR, and the like. Plug in the thyristor SCR. When the button AN is pressed, when the 555 outputs a high level, the LED, the resistor R4, the thyristor SCR, and the transistor BG2 form a closed loop, and the LED 1 is illuminated; when the 555 outputs a low level LED2, R4, SCR, BG1 form a closed loop, and LED 2 emits light, indicating that the thyristor is good.
After inserting the thyristor SCR during the test, the LEDs LED1 and LED2 should not be lit, otherwise the two poles of T1 and T2 are shorted. The multivibrator has an oscillation frequency of f=1.44/(R1+2R2)C. The oscillating frequency corresponding to the illustrated parameters is approximately 1 Hz. Since R1<<R2, the time t corresponding to the charging of the capacitor C is charged to. 693 (R1+R2)C, which is very close to the time t corresponding to the discharge of the capacitor C = 0.0093R2C, so the duty of the pulse generator output pulse The ratio is close to 1:1.
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