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Thread: Triacs

  1. #1
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    Triacs

    I am giving an in house training next week and I would like to include triacs in the class. I am looking for some good lit on what they are and how to test them that I can give out.
    Thanks.
    "It's always controls"

  2. #2
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    http://en.wikipedia.org/wiki/TRIAC
    With no gate voltage applied the thing should look like a high impedance in both directions. With a 9v battery through a 390 ohm resistor into the gate it should look like a low impedance in both directions.
    The batt neg. term. goes to A1, the resistor goes to G.

    http://www.quasarelectronics.com/sma...iac-tester.htm
    You could probably make your own tester with a 24vac xformer, a 24v incand. lamp and the two components above.

    Or, even better, buy a lamp dimmer.
    Get the part number off the triac inside to get a data sheet from the Web and figure out which is A1, A2 and G (or just figure it out from the wiring) and then use this dimmer as a test bed.
    The triac under test, fastened with 3 clip leads, substitutes for the internal triac (which you removed).
    These dimmers can handle 600w because the triac is on a heat sink. For the test triac with no heat sink I'd use a 25w incand. lamp, max.
    Of course, the first triac you test should be the one you just removed.

  3. #3
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    Quote Originally Posted by WhoIsThat? View Post
    http://en.wikipedia.org/wiki/TRIAC
    With no gate voltage applied the thing should look like a high impedance in both directions. With a 9v battery through a 390 ohm resistor into the gate it should look like a low impedance in both directions.
    The batt neg. term. goes to A1, the resistor goes to G.

    http://www.quasarelectronics.com/sma...iac-tester.htm
    You could probably make your own tester with a 24vac xformer, a 24v incand. lamp and the two components above.

    Or, even better, buy a lamp dimmer.
    Get the part number off the triac inside to get a data sheet from the Web and figure out which is A1, A2 and G (or just figure it out from the wiring) and then use this dimmer as a test bed.
    The triac under test, fastened with 3 clip leads, substitutes for the internal triac (which you removed).
    These dimmers can handle 600w because the triac is on a heat sink. For the test triac with no heat sink I'd use a 25w incand. lamp, max.
    Of course, the first triac you test should be the one you just removed.

    to test triacs i use 2 rib relays and watch the lights.
    IV IV IX

    use your head for something other than a hat rack.......Gerry

  4. #4
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    Quote Originally Posted by viceman View Post
    to test triacs i use 2 rib relays and watch the lights.
    What is. . .?
    You also want to check the range of control, I guess.

  5. #5
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    IV IV IX

    use your head for something other than a hat rack.......Gerry

  6. #6
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    Quote Originally Posted by skwsproul View Post
    I am giving an in house training next week and I would like to include triacs in the class. I am looking for some good lit on what they are and how to test them that I can give out.
    Thanks.
    Well, I'm not sure just how deeply yah really want to dig into the inner workings of semi-conductors.

    But maybe some of the following links might be helpful.

    Gallawa's site.

    http://www.gallawa.com/microtech/triac.html

    The guy has some hints about testing triacs. Specifically about the kind of triacs used in microwave ovens. But same principle applies to most all of them.

    Note specifically, his hints on how to distinguish one terminal from the other. [1] If all three are different sizes, the gate is usually the smallest, and (M)T2 is usually the largest. [2] If there is a screw down tab, it is usually connected to (M)T2. And [3] an ohms check will usually show 10 to 300 ohms between the Gate and (M)T1, whereas infinity will be the normal reading between (M)T1 and (M)T2 or between Gate and (M)T2.

    None of those are ALWAYS true, but they apply better than 95% of the time.

    Allen-Bradley (Rockwell) PDF paper talking about testing triacs with an ohmmeter.

    http://www.ab.com/support/abdrives/d...on/fb/1012.pdf

    Tony van Roon's site talking about SCR's and Triacs. He also shows a way to build a simple tester. Note from me, a 9V battery should work as well as a 12V. Most Triacs you'll run into will switch "On" with a gate voltage somewhere between 1 and 5 volts:

    http://www.uoguelph.ca/~antoon/tutor...cs/triacs.html

    A couple links to AllAboutCircuits where SCRs and Triacs are discussed

    Triac
    http://www.allaboutcircuits.com/vol_3/chpt_7/6.html

    SCR
    http://www.allaboutcircuits.com/vol_3/chpt_7/5.html

    I hope something in the above helps yah out.
    A site where I stash some stuff that might be interesting to some folks.
    http://cid-0554c074ec47c396.office.l...e.aspx/.Public

  7. #7
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    forgot

    Usually the gate cannot turn off the triac; the current through the A1 A2 terminals needs to go almost to zero to do this, but there are GTO (gate turn off) devices.

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