Hi Tracy- I was going to say the same thing but didn't want to risk making an ass of myself in case there was some kind of magic software I didn't know about. One possible way to protect against spikes is to use zener diodes across the power input. Let's say you want a maximum of 5 volts going into a device. OK, so get two zener diodes at anywhere between 5 to 6 volts, and connect them "head to head" (facing each other) and connect the "tails" across the power input to the device. Anything over 5 volts causes one or the other of the zeners to avalanche and conduct as a short. I would also have current-limiting resisters in series with both power leads both before and after the zener diodes, because when the zeners avalanche, they effectively become a short circuit, and that will cause a current surge from the power supply. But with resisters in series, the resisters limit the maximum current draw, whether it's by the device itself, or by the zener diode avalanching due to a spike. OK, so here's a crappy attempt to draw a schematic in ASCII. Resisters R1 limit current input when the zener diodes avalanche. Resisters R2 limit the discharge of the capacitor C1 so it doesn't fry when the ZDs avalanche. C1 is an electrolytic capacitor to store a charge that maintains power to the device during brief spikes when ZD has avalanched and the power level toward R2 has decreased. Power supply output + ----- R1 ------ R2 ------ device power input + | | ZD | | C1 ZD | | | Power supply output - ----- R1 ------ R2 ------ device power input - Calculate the value of resisters R based on the current level you need to draw for the device, and the value of C1 based on the power needed by the device during a momentary spike. Hope this helps... -George ====== On 13-02-25-Mon 9:28 AM, Deno Vichas wrote: