You have to look at the transients of your power supply. If you do not have a seperate power source for your controls, and the valves, you will get spikes on your power. One way is to use opto-couplers between the dirty power on the valves, and the control power. We built robotic controllers, and had problems with static RAMS that would erase because of pneumatic valves. Finally went to EPROMs, and that cleared up the problem. Huge EMF surges occur when a valve opens. Clamping diodes help, but you still get surges on the line. -----Original Message----- From: Andrew Warren To: PICLIST@MITVMA.MIT.EDU Date: Tuesday, March 10, 1998 8:10 PM Subject: Re: Semi random reset Javier Puiggros Vogel wrote: > I have a pic16c74A connected to 4 PCB relays (5V) to open valves for > humidity control, but sometimes the program reset and start again. > The reset happen when the solenoid valves turn off. I tried using > some caps in mclr and vdd pins but the problem don't go. I don't > know if there is an special values for the caps, or another solution > than putting caps in the pins processor some help? Javier: Do you have diodes across your relays? -Andy === Andrew Warren - fastfwd@ix.netcom.com === Fast Forward Engineering - Vista, California === http://www.geocities.com/SiliconValley/2499