How about placing a diode in a trace from the 12V to the input of the = regulator ... and another from the battery to the input of the reg. When the the 12V drops the power will be supplied by the battery. Does anyone see a problem with the reverse current through the battery = diode damaging the battery?=20 >>> kcer@COGECO.CA 01/30/02 11:48AM >>> Can anyone point me to any design notes on a regulator or circuit that = will switch my 5volts to a 9v battery to power the 16f84 chip when the = incoming 12v power is missing? Regards, Steve -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body