relay drive circuit on low power supply voltage

Published:2011/7/14 23:16:00 Author:Fiona | Keyword: relay drive, low power supply voltage | From:SeekIC

V1 is unijunction transistor BT33C,it composes the relaxation oscillator with R1, R2, R3 and C1,SCR is one-way controlled silicon,when press the start button AN1,the circuit is energized,because the SCR has no trigger voltage,the circuit is not conducted,the relay J doesn't move,the power charges the capacitor C2 to close to supply voltage through R4 and VD1(Vcc-VD1 drops).Meanwhile,the power R1 charges the capacitor C1. After a few seconds,the C1's voltage is charged to close to the trigger voltage of V1, C1 discharges immediately through V1 and forms a positive pulse on the R3, this pulse is all the way added to the V2 base to make the V2 be quickly saturated conducted,V2 collector namely capacitance C2 positive closes to ground.



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