good luck with the cap and the zener.... youre going to find that the inrush current kills one or the other if switched via outlet socket often. I would recommend that one puts either bead inductance or resistor in series with the cap and diode. The circuit however is very novel and in the past, i have used it to provide zero crossing ( for 50hz clock appliance ) and dimmers ( accuracy not required ). The reason its not quite working right is because the 5v you are using to trigger is not referenced to the 0v/neutral of the triac. This means that if yuo use an external supply, the 5v would be seen to be changing with reference to the 0v due to the ac feeding the lamp. this will give rise to triggering in the incorrect quadrants, or flicker slightly, but essentially be on. I can give a circuit from elektor on trafo-less mains which i have used before, without any issues, should it be required. PLEASE PLEASE PLEASE put 2 resistors in series across the 220n cap, you will that way avoid catastrophic events should one resistor fail short circuit ( preferably use flameproof) .The remaining one will still work and wont/shouldn't mess with the power dissipation of the zener. AND you will avoid a nasty shock ( which i didn't) when prodding with the power off :) J ----- Original Message ----- From: "zantos" To: Sent: Thursday, August 07, 2003 1:38 PM Subject: [PIC]: Light PIC > Need some help from the Triac experts.....the attached cct powers a PIC. It > is cheap and dirty set-up. When I take the triac i/p to 5v the lamps lights. > When I take the triac input to 0v the traic also lights but leave the i/p > open the triac goes out. Appreciate some help explaining why this happends > or where I am going wrong?. BTW I am trying this without pic in place and > just shorting to 5v or 0v. I just want to switch the lamp off from the PIC > powered from the lighting circuit. > Any reply most appreciated. > z > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. > > > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.