you need a datasheet: e.g. http://www.st.com/stonline/books/toc/ds/336.htm You can see the terminals A1 A2 and G in the picture :-).
Normally the gate threshold is approx 1 volt @25C (with my T1235 here). Simply try it out. I think it depends on terminal voltage (can be 600V) temperature and so on. Some of your parameters are fixed and known; so it is not a big problem. Matthias On Wed, Feb 12, 2003 at 12:56:19PM -0800, Robert Ritchey wrote: > Hi Matthias, > Sorry to bother you again with this but the Triacs I found in Digi-Key > (which I am pretty much reliant on for prototyping) have gate thresholds > of 0.2V at 110C to 2.0V at 25C. Some are higher at 2.5V You mentioned > a 1.0V threshold. Also, I am not sure what A1 and A2 are connected to. > Is A2 ground and A1 my input voltage? Like I said, I know nothing about > Triacs and have no literature on their operation. The data sheet is not > a lot of help. > Thanks, > > At 01:25 PM 2/11/03 -0800, Matthias Weingart wrote: > >On Tue, Feb 11, 2003 at 12:39:12PM -0800, Robert Ritchey wrote: > > > Thanks for the feedback on my options. I am not familiar with the > > > Triac/zener circuit. In fact, I have never used a Triac. Is it just > > > as you describe it below, Polyswitch in, Triac with a 4.5V (or close) > > > zener on the gate with a 1nF cap? > > > >Right. (Low power) Zener between A2 and gate, 1nF between A1 and gate. Very > >simple. Your circuit would never get killed; but however the wrong power > >supply could be cooked. > > Dimensioning for 5 volts +-10% is difficult. Regulated power supplies > >delivers 4.5 to 5.5 volts; choosing 5.1 zener +0.2...1.3 volts Triac > >threshold will result in 5.3...6.4 volts for the triac getting fired. So > >your device could be switched off from your normal supply too. I would > >choose a 5.6 zener. (check the datasheets and the tolerances of zener and > >triac). > > > >M. > > > > > > > > At 12:14 PM 2/11/03 -0800, Matthias Weingart wrote: > > > >On Tue, Feb 11, 2003 at 07:59:27AM -0800, Robert Ritchey wrote: > > > > > > > >My favourite solution is a combination of Polyswitch, Triac and Zener > > at the > > > >gate of the Triac. This will protect from reverse power (<1.5V) and > > > >overvoltage (zener voltage + 1V triac gate threshold). Do not forget a > > > >capacitor (1nF?) from gate to ground, to protect from firing because > > of fast > > > >rising input voltages or very short spikes. In case of fault, the current > > > >flowing is only at the rated level of the Polyswitch and the power in the > > > >triac is very low (1.5volts * polyswitch current). > > > > > > > >I remember there was a component called TRISIL that worked in this way. > > > >But I think this is no longer available (why?). > > > > > > > >However I would always use a regulator on the board for the 5 volts +-10% > > > >for a wide input voltage range and use a unregulated wall socket. That > > also > > > >solves problems with the sometime quite high voltage drop over the poor > > > >poor DC plugs. > > > > > > > > Matthias > > -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). > 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).
