Well, it took 4 hours, one 555, 3 resistors, 2 diodes, 1 cap, a piece of perf board and several inches of solder. It's alive! When there's no data flowing on the serial port, the relay stays energized (I'm using a small, low current reed relay). All it takes is 1 or 2 characters to de-energize the relay for a few seconds. I'm going to try it out at the office next week. I just hope it doesn't burn out the serial port... Thanks for the help Barry ----- Original Message ----- From: "Aaron K" To: Sent: Friday, February 22, 2002 6:47 PM Subject: Re: [PIC]: Serial Port Powered WDT > Something that I think would work well and be very low power (and simple) > would be to make a small one shot timer out of a 555 (the monostable setup) > thas is triggered by the first RS232 '0' bit in the byte (which would be a > +5 to +17 or so DC). So you could set up the timing so once this '0' bit is > recieved, it would start the 555 timer triggering the relay. Then, when ever > you wanted to turn on the relay, you'd just send any byte out (as long as it > has a '0' bit in it) on the serial port. You wouldn't need a RS232 converter > either, just hook up the RX pin directly to the 555 with a resistor and > (probably) some protection diodes, similar to the way the PICs do it on > their pins. > > Aaron > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics > > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.