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Delay lamp circuit using relay (2)

2016-08-11 07:56  
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Delay lamp circuit using relay (2)
As the figue shows, it is a delay lamp circuit using relay with good perfomance. Press down SB to makelamp E light. At the same time,the 220V AC passes capacitance step-down half-wave rectifying and voltage-stabilizing circuit composed of VS, VD1,C1,C2.The C2 ends outputvoltage is 12V. Three transistor VT1 base is relay contact k-1 grounding and stop, so VT2 conductive, electric relay K. Contact k-1 backward often start, the key SB short circuit self-locking, so the release SB, light E can still be energized to emit light. The positive power supply by RP, R3 to C3 the VT1 capacitor charging base potential gradually raised, when raised to a certain degree, the VT1 conduction, VT2 VT1, VT2 cutoff, which consists of the Schmidt circuit turned back to the original state, the relay K release, contact k-1 reset lamp E power supply circuit is cut off and the lights went out.