Brevor Member Jun 20, 2013 #2 I think D3 is backwards in your schematic. I believe C1, R3 and Q2 provide a trigger pulse to the 555, D3 if turned around would quickly discharge C1 when SW1 is closed.
I think D3 is backwards in your schematic. I believe C1, R3 and Q2 provide a trigger pulse to the 555, D3 if turned around would quickly discharge C1 when SW1 is closed.