the quick SCR testing machine composed of 555

Published:2011/9/8 6:15:00 Author:Ariel Wang | Keyword: SCR, testing machine | From:SeekIC

The oscillation frequency shown in the chart is about 1Hz.The charging time t of the capacitor C =0.693(R1+R2)C.The discharge time t of the capocitor C =0.693R2C.They are quite alike.So the duty cycle of the output pulses is near 1:1. LED1,resistor R4,SCR,transistor BG2 form a closed circuit when 555 outputs high level as AN is pressed and SCR is plugged in.LED1 gives out light.LED2,R4,SCR and BG1 form a closed circuit when 555 outputs low level.LED2 gives out light.It indicates the SCR is good.



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