Peak Blocking Current

Discussion in 'General Electronics Chat' started by Nanto, May 24, 2016.

  1. Nanto

    Thread Starter New Member

    May 23, 2016
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    Hi everyone. I have a question I'm finding hard to clear out: what is the peak blocking current?

    I'm working with a triac optoisolator and I'm not quite sure about this characteristic. I'm using two triac's at the optoisolator output, and I want to use more if possible but I need to understand this concept in order to continue with my calculations.

    Any help will be well received. o_O
     
  2. Nanto

    Thread Starter New Member

    May 23, 2016
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    Is it the max current flowing into the optocoupler when it is in off-state?
     
  3. dl324

    Distinguished Member

    Mar 30, 2015
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    Welcome to AAC!

    Yes, max TRIAC leakage when off.
     
  4. Lestraveled

    Well-Known Member

    May 19, 2014
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  5. Nanto

    Thread Starter New Member

    May 23, 2016
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    @dl324 @Lestraveled

    First of all, thanks so much for your help.

    I have been reading the pdf Leastraveled left in the reply above. It has been of so much help. But while reading I've trying my circuit. I'm triggering 3 triacs [2n6071A (4A/200V)]from the same optocoupler. With 2 triacs everything's fine. But with 3 I'm not quite sure.I attached a chart with voltage and current measurements I get at the optocoupler's output with 1, 2, and 3 triacs. When I did it with 3 triacs I couldn't read the current, I guess is too small? Below the chart I wrote what I think should be the current in those conditions.

    I noticed one of my lamps doesn't shine the same as with 2 triacs, I guess is due to power consumption?
    Should I continue with 3 triacs? Or should I stop with 2? I'm quite sure I can't do it safely with 4.

    By the way, my goal is to control 8 lamps so I guess my circuit would be with 2 triacs per optocoupler in order to be functional.

    Thanks so much again for any help.
     
  6. Lestraveled

    Well-Known Member

    May 19, 2014
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    @Nanto
    The trigger voltage is a little different with each triac so, you will need a resistor is series with each gate.
     
  7. Nanto

    Thread Starter New Member

    May 23, 2016
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    @Lestraveled

    I guess they have to be a smaller resistor than the one I used (470 ohms). One more question they have to be different in order to trigger each different triac right? Are the triacs different because they aren't ideal am I right?

    If this is correct, can I still adding more triacs to the same optocoupler?
     
  8. Lestraveled

    Well-Known Member

    May 19, 2014
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    1,215
    @Nanto
    No, the resistors should be the same value. What actually triggers the triac is current at a trigger voltage. If one triac triggers at a higher voltage, the other two triacs might prevent that triac from triggering. Resistors balance this out between triacs.

    You will have to look at the specs for the triac gate current and the opto-isolator current to determine if you can add more triacs.
     
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