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how to trigger BT136

Discussion in 'General Electronics Chat' started by kris1, Mar 5, 2008.

  1. kris1

    kris1 New Member

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    i had a problem while designing a circuit in which BT 136TRIAC has to be triggered from a half rectified current of 30 mA at about 6V. Its not getting triggered. Even for this supply my trigger circuit is consuming power as the 4.7k 10W resistor is getting heated up so fast.Suggest me a way to trigger it.
    The circuit is about "Solid state auto power off on mains failure".
    Even Itried this in ORCAD capture but this didnot work. Can anyone share my pain...
    the circuit is available at http://www.electronicsforu.com/efylinux/circuit/cir81.gif
     
    Last edited: Mar 10, 2008
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  2. Hero999

    Hero999 Banned

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    do both circuits have a common ground?

    Are you trying to use the secondary of a 6V transformer without the other side connected to the supply you're trying to switch?

    Please post the schematic.
     
  3. kris1

    kris1 New Member

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    thanks for response

    thanks for your response.
    the circuit is available at the folowing site please
    http://www.electronicsforu.com/efylinux/circuit/cir81.gif
     
  4. dave

    Dave New Member

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  5. em2006

    em2006 Member

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    In my opinion the schematic contains an error. The R7 (triac gate series resistor) is too big (270K).
    When transistor T1 is open, the 9V voltage is applied to gate, via this resistor, so max current is no more then 9V/270kOhm=0.03mA.
    Use a 270 OHM resistor instead, to increase current to 30mA.
     
  6. em2006

    em2006 Member

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    About my previous post, the schematic is here:


    [​IMG]
     
  7. em2006

    em2006 Member

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    Just now I see another errors...
    The T1 base-emiter junction and the S1 pushbutton are permanently shorted because the marked link:

    [​IMG]
     
  8. Sebi

    Sebi New Member

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    This is not a correct design... and many energy dissipated.
    Triacs don't like the positive DC trigger, most of case fired only half-wawe - depending of load.
    I strongly recommend to use an optotriac for firing (eg MOC3041, it contain zero-cross feature). In PSU use a serial capacitor (100nF X2 type) and a bridge rectifier.
     
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  9. Bob Scott

    Bob Scott New Member

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    Why are you switching Neutral to Ground?
    Why do you have a load connected between Hot and Ground?

    This will surely trigger any ground fault circuit breaker.
     
  10. ecerfoglio

    ecerfoglio New Member

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    Do Not Connect "Ground" To "Earth Ground"

    I think that the GROUND symbol in the schematic is just a "cero volt reference" for the circuit.

    It is certainly :eek: NOT connected to EARTH GROUND:eek:

    If both "grounds" were connected, not only will trigger any ground fault circuit breaker but will be a dangerous system (and will be an "allways on" switch:D )
     
  11. em2006

    em2006 Member

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    I think the same.
    In the schematic ( http://www.electronicsforu.com/efylinux/circuit/cir81.gif ) we can see TWO TERMINALS used only: PH(ase) and N(eutral). The earth ground terminal (PE) is not present in the schematic, because is not used.
    In this schematic, the mentioned symbol shows the common neutral trace via triac , and represents, of course, a reference for the circuit, but not earth ground. The well known symbol "earth ground" was not properly used.


    [​IMG]
     
  12. eblc1388

    eblc1388 Active Member

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    Why would someone want to build a "SolidState auto power off on mains failure" circuit using discrete components?

    A simple AC relay with a self hold push button will do and probably more reliable, consumes much less energy and generates less heat.
     
  13. kris1

    kris1 New Member

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    very good response

    Thanks for all. Till now I felt im the only person to think about such challenging things. But I had many friends. im happy.
     

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