Bill, Did you add any diodes across the relay coil (anode to gnd, cathode to +12VDC)???? The diode provides path for current to flow once the 12 volts is removed. Remember the coil is just a big inductor. +12DC --------+-------+ | | --- --- /_\ | | Relay coil | --- | | GND --------+-------+ Hope this helps! -Randie ________ Randie Ohtsji / ____/ /__ ____ ____ ___ _________ email: rohtsji@glenayre.com / /___/ / _ \/ __ \/ __ `/ / / / __/ _ \ Glenayre R & D / /_\ / / __/ / / / /_/ / /_/ / / / __/ Vancouver, B.C. CANADA \____/_/\___/_/ /_/\__,_/\__ /_/ \___/ Phone: (604) 293-1611 x4555 ________________________/ / Fax: (604) 293-4317 /_________________________/ > From BRYSOWG@TEXACO.COM Wed Jan 21 12:43:33 1998 > X-Priority: 3 > Mime-Version: 1.0 > Date: Wed, 21 Jan 1998 14:43:02 -0600 > From: "Bryson, William G (Bill)" > Subject: [OT] Reed Relay problem for 16C84 based truck light bar scroller > To: PICLIST@MITVMA.MIT.EDU > > I am using a 16C84 PIC to create a light bar for the 5 marker lamps (Cabover > lights) on top of a Chevrolet Truck. The lights scroll left or right when > that respective blinker is on. They also all blink in sync with the > Emergency Flashers and are all on solid with when the parking lamps are on > (with no blinker or flashers). For the record, I have 3 inputs: left / > right blinker, and parking lights. > > The 5 light outputs from the PIC are input into a 74LS04, Hex Inverter. The > 5 outputs of the Hex Inverter drive the coils of 5 Radio Shack 5VDC Reed > Relays (part# 275-232). The relay contacts are passing 13 to 13.8V to the > lights. The current for each light is about 275ma (.275 Amps). > > The problem is the CONTACTS of the reed relays are sticking intermittently. > Any of the 5 contacts may stick. The coil voltage is not the problem. The > contacts may still be stuck after powering down the circuit and powering > back up without any power to the coil. I have also shorted the coil while > the contacts are stuck to no avail. > > Heat is NOT the problem for the sticky contacts. The contacts have become > stuck immediately after the entire system had sat for hours. However, > sometimes it is necessary to cool the system for several seconds to unstick > the contacts. > > I would appreciate any technical input anyone might be able to provide. > > On a lesser note, I have been unable to locate the manufacturer of the > relay. There is an 'OMR' or 'DMR' and a 'DEG' name on the relay. Any ideas > on who and where this company is located. > > Thanks.... > > ------------------------------------------------- > Work all day & night, > deliver on time & on budget, Regards, > and justice for all... Bill Bryson >