Funny thing happens when you try and protect against idiots. The world comes up with a better idiot.
Bob, there are many crowbar devices on the market that will limit the voltage to some definable level. However I think there are several issues this approach surfaces. What will limit or interrupt the current? A crowbar circuit will keep drawing current until something shuts it off. Wall warts are designed to be current limiting but not usually current interrupting. I can foresee a scenario whereby both the wall wart and the crowbar sit there and cook. I have seen units with crowbars that still burned up. An approach that has worked for me is to use an AC wall wart and board mounted bridge rectifier, capacitor, and an onboard regulator. This allowed me to define the regulation and noise on my 5 volts and allowed the customer to use any wall wart that would fit the funny little coaxial power plug. Fred Townsend Robert Ritchey wrote: > Hi, > I have a question about protecting a circuit from an overvoltage > condition. We > have a new device that we are planning to use a regulated 5V wall-wart type > device for power. They have also requested overvoltage protection in case > someone plugs in a 6V or 8V unregulated supply by accident. My expertise > is mostly digital so I am not sure what the best and cheapest way to do this > would be. Thanks in advance for any help or pointers. > > -Bob > -------------------------------------------------------------------- > Robert Ritchey > Quest Engineering & Development > 1328 East Cottonwood Lane > Phoenix, AZ 85048-4765 > Tel: (480) 460-2652 > FAX: (480) 460-2653 > E-Mail: [EMAIL PROTECTED] > E-Mail: [EMAIL PROTECTED] > E-Mail: [EMAIL PROTECTED] > E-Mail: [EMAIL PROTECTED] > WWW: www.QuestEngDev.com/ > WWW: www.Smart-Fly.com/ > -------------------------------------------------------------------- > > -- > Author: Robert Ritchey > INET: [EMAIL PROTECTED] > > Fat City Network Services -- 858-538-5051 http://www.fatcity.com > San Diego, California -- Mailing list and web hosting services > --------------------------------------------------------------------- > To REMOVE yourself from this mailing list, send an E-Mail message > to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in > the message BODY, include a line containing: UNSUB CHIPDIR-L > (or the name of mailing list you want to be removed from). You may > also send the HELP command for other information (like subscribing). -- Author: Fred Townsend INET: [EMAIL PROTECTED] Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB CHIPDIR-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
