At 11:42 AM 12/26/2003 +0000, you wrote: >Hi Everyone, > >I'm having a few problems getting my triac to turn on through an >opto-triac. More specifically, the opto-triac is turning on and putting >mains voltage at the triac's gate, but the triac won't start conducting. > >A schematic: > >+5vDC 240vAC (live) >|-R1---LED1---| |------R2-----|------------| > | | | > LED2 TR1 TR2 > | | | | >--------------| |------------- -------LOAD-| >Gnd Neutral > >R1 200 Ohms >R2 5.6K >LED1 Red indicator LED >LED2 MOC3041 opto-triac >TR1 MOC3041 opto-triac >TR2 BTA16-600 Triac (16A, 600V) > >My LOAD is a 60W table lamp I'm using for testing. > >I'm a bit nervous of experimenting too much with this because I've already >welded my meter probes together and flipped the house electrics off >yesterday, and if it wasn't for my (now black and sooty) safety goggles, >I'd be very unhappy. > >TR2's data sheet says it needs a max 50mA of gate current to turn on, Unless you are operating in the pesky quadrant IV (in which case, 100mA), which you are not. >and 240/5600 is 42mA. Peak voltage is 1.41 * 240 =3D 340V, so current is 61mA at the peak of the AC line before the load turns on. Note: You really should be using more like 100R than 5K6. You want it to turn on near the beginning of the AC cycle, not some poorly determined time around 1/4-1/2 way through (getting earlier as the thyristor heats up), right? Note that the 100R will BURN UP if the triac does not turn on so you need to use a flameproof type for safety. This will also take out the MOC, most likely. > From the datasheet's graphs, it looks like the >minimum Igt is 16mA. I've tried it with a 9.6K resistor in there and a >fresh triac, but still no light. > >I've read up as much as I could find on interfacing to triacs, and (to me) >mine looks OK. > >Any ideas of what I'm doing wrong? I suspect you have MT1 and MT2 swapped. Also, how did you calculate the 200R? You need to guarantee 15mA (@25=B0C, MORE at lower temperatures) through the LED for this part to be guaranteed to work. Best regards, Spehro Pefhany --"it's the network..." "The Journey is the= reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body