On Thu, Feb 13, 2003 at 09:45:24AM -0800, Declan. Moriarty wrote: > I had backed out of this one, but now feel like getting back in. A triac is > an A.C. device, with two scrs back to back. Why is it suggested as a > crowbar? Probably in case you had an A.C wall wart. Personally, I think > it's not the way to go at all. The idea with a triac is that you control > A.C. I would use an SCR if you have to have a crowbar. I would never try
A Triac is a bidirectional version of a SCR. The SCR is conducting only in one direction, the Triac in both (to protect from reverse voltage). In fact I modified a simple SCR crowbar with a Triac to get the reverse voltage protection. > to fire one with simply a zener. Gates get sensitive in the heat ... My Triac needs some 10 mA to get fired. With heat I have some uA in the zener ... but you can add some resistors (see link below). I used google.com with "triac crowbar" and got a Powerpoint presentation, (the first link). There is a page with a "Triac crowbar". Instead of my zener it uses a DIAC and R-network (to cut out voltage spikes above 120 V). It is very similar to my solution. (you can download a powerpoint viewer from microsoft) The using of a SCR as a crowbar is described here (in german): http://www.e-online.de/public/schaerer/crowbar.htm Maybe googles translator can help you to understand it: http://translate.google.com/translate?u=http%3A%2F%2Fwww.e-online.de%2Fpublic%2Fschaerer%2Fcrowbar.htm&langpair=de%7Cen&hl=de&ie=UTF-8&oe=utf-8&prev=%2Flanguage_tools Matthias -- Author: Matthias Weingart 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).
