Harold Hallikainen wrote: > Placing the SCR in a FW rectifier seems to be a worse solution (to > me) than using a triac. You'll get two diode drops plus the SCR drop, > which I believe would be considerably higher than the drop on a triac. Depends on the load. For driving transformers or AC motors, this is the only way to do it in order to achieve symmetrical triggering, though the half-wave supply for the operating voltage would not be satisfactory - perhaps a secondary regulator. > Also, the drive circuit floats a bit wildly since the negative > side of the bridge is now alternately connected to each of the AC > terminals of the bridge, depending on line polarity. Yes. It doesn't solve the isolation problem at all. Best for small, encapsulated products such as stand-alone knob-operated dimmers/ power controllers. >>From: Peter van Hoof >> how about this solution >> http://www.vertonet.com/members/pvh/scr.pdf >> get power for the pic from the other side of the load with diode, cap >> and resistor in series. Did *no-one* notice the blooper here? Did anyone look? D5 is on the *wrong* side of D6. -- Cheers, Paul B.