On Thu, 4 Apr 2002 12:07:58 -0500 Chris Loiacono writes: > Thanks, Bob. > The SCR controller I am starting with is a successful digitally > controlled > phase-angle design I did a year or two ago, and it is completely and > redundantly isolated and snubbed for 460/480V lines. I needed to > convert it > into a Triac controller (or rather to add the ability.) > > My difficulty was that I was confusing the definitions of quadrants > for > gating. Once I got that straight, I found that the same board will > gate > SCR's, Triac's and Alternistors with only different external wiring > to the > control devices and changes in gate resistors. Since it already has > terminals for connecting to large (100'S of Amps) SCR's on > heatsinks, I will > add holes to the boards for the smaller tabbed devices. Something we did for triacs in the Shoebox series of dimmers (http://www.dovesystems.com/BuildPage.php3?page=shoebox) is to "surface mount" the triacs. The triacs are off the board (mounted on a heat spreader attached to the cabinet), but the leads are soldered down to pads that look like edge connector fingers. Another product used to have typical pads with holes for the triacs, but since triacs need to be replaced when the user plugs in shorted loads, these pads were quickly destroyed. This "surface mount" of the triac leads has worked out well. We've also used it in a board redesign of the SceneMaster (http://www.dovesystems.com/BuildPage.php3?page=sm). Note that I had also tried TO-220 sockets (the kind where you crimp terminals on wires, then poke them in the socket, then plug the socket onto the heat sink mounted TO-220). These proved unreliable at the currents we're running (5-10A). The spring contacts eventually get a little weak, then the resistance goes up, temperature goes up, resistance goes up... and it fails. Harold FCC Rules Online at http://hallikainen.com/FccRules Lighting control for theatre and television at http://www.dovesystems.com ________________________________________________________________ GET INTERNET ACCESS FROM JUNO! Juno offers FREE or PREMIUM Internet access for less! Join Juno today! For your FREE software, visit: http://dl.www.juno.com/get/web/. -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body