555 household appliance products long timing circuit

Published:2011/6/7 1:40:00 Author:TaoXi | Keyword: 555, household appliance, products, long timing | From:SeekIC

As the figure 15-18 shows, the astable multivibrator is composed of the IC(555) and VT1, VT2, R1, RP2, R4, C2, the oscillation period T=0.693(R1+RP2+R4)C2. Because the b electrode of VT2 connects to the pin-3 of IC, so when pin-3 outputs the high electrical level, VT1 is a constant-current charging source, it has good charging linear and timing precision. Because it uses the bipolar type 555, so it can drive the SCR directly. When the IC outputs the high electrical level, the load gets power to work, when the IC outputs the low electrical level, the load has no power to work. The timing circuit is composed of the VT3 and RP1, C1, DW1.etc. The VT3 uses the VCMOS type tube V40A or TO-220.



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