----- Original Message ----- From: "Peter L. Peres" To: Sent: Tuesday, January 07, 2003 7:40 PM Subject: Re: [PIC] Multi-zone external light controller with softstart > On Mon, 6 Jan 2003, Spehro Pefhany wrote: > > *>that will allow a circuit breaker to blow before the triac goes > *>(think hockey-puck sized). > > Or use an inexpensive triac that can be replaced easily (unlike our dear > friends in the far east who bolt it on the heatsink instead of using a > screw). > > There is a way to protect scrs from shorts, but it uses another scr > (identical to the first) and driving it is not very easy. Triacs are notorious devices - there isn't a "fast-blow" fuse in existence that will fail faster than a triac! I have always used back-to-back thyristors in anything that needs to be more reliable than a domestic lighting dimmer - the drive circuit configuration is more complex but the reliability is increased by a few orders of magnitude. Chris -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.