At 08:19 PM 6/16/2011, james tornes wrote: >I have an interesting problem. I have a mains circuit that looks like this= : > >mains---110VAC--+ on/off switch +-------------------+ load >+----------mains return Question: does your wiring include a protective ground? If it does, you can parasite the power you need from the always-live=20 110Vac line and the protective ground. You must keep the total current consumption on the protective ground=20 below some limit (don't recall what that limit is but assume that it=20 is less than 1mA). You can use either a capacitive-type dropper and live with the tiny=20 current available or use an efficient switcher and get some real=20 current @ 5V (1mA @ 110Vac ~=3D 20mA @ 5V). Some electrical codes don't allow this - but I do see=20 commercially-available devices that work this way. dwayne --=20 Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax www.trinity-electronics.com Custom Electronics Design and Manufacturing --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .