delaying a zero voltage pulse for triac circuit

Discussion in 'General Electronics Chat' started by Cbaz, Mar 8, 2010.

  1. Cbaz

    Thread Starter New Member

    Oct 27, 2009
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    I have been looking at using a circuit that delays a zero voltage switch pulse to control a triac. I know this can be achieved by writting code for a microcontroller. I have no experiance of writting microcontroller code so am looking for an alternative method to generate a controlled delay of the zero voltage pulse. If the pulse occurs every 10 ms what sort of circuit would allow me to delay this pulse. would a 555 timer circuit be adequate
     
  2. retched

    AAC Fanatic!

    Dec 5, 2009
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    Is your zero voltage pulse a pull down to ground? or would that work for you?
     
  3. beenthere

    Retired Moderator

    Apr 20, 2004
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    What you may need to do is to sense the zero crossing and use that event to trigger the delay.
     
  4. t_n_k

    AAC Fanatic!

    Mar 6, 2009
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    You could look at a typical triac light dimmer circuit such as this

    http://www.electronics-project-design.com/Light-Dimmer-Circuit.html

    which might give you some ideas.
     
  5. Cbaz

    Thread Starter New Member

    Oct 27, 2009
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    Thanks for the advice. I have looked at typical dimmer circuits T N K using RC diac combination. I am trying to look at alternative methods to this type of triac control. I have got a circuit that senses zero voltage crossing and produces a voltage pulse at this zero cross instant. Im am looking for a circuit that will give me a control delay of this pulse and hence control over triac firing angle
     
  6. Cbaz

    Thread Starter New Member

    Oct 27, 2009
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    the circuit mentioned above is shown in the attatched schematic aswell as an oscilloscope showing the traces.
     
  7. retched

    AAC Fanatic!

    Dec 5, 2009
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    Could you use a 555 and trigger it from your zero cross pulse?

    Or is it the same signal you are trying to extend the 0v time?
    If that is the case, you could hold the line to ground for the determined amount of time. At the zero pulse moment, the 555 could sink the current for a user setable amount of time, holding it to 0v until closed.

    What types of current are you dealing with?
     
    Last edited: Mar 11, 2010
  8. Cbaz

    Thread Starter New Member

    Oct 27, 2009
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    I am trying to get a new pulse delayed between 1ms and 10ms with reference to the zero voltage pulse. The time between the zero voltage pulse and the delayed pulse will act as my fire angle delay for the triac. I have tried looking for a 555 circuit that would do this but have been unable to find a suitable one so far. Im not sure what you mean sorry by extending the 0v time
     
  9. retched

    AAC Fanatic!

    Dec 5, 2009
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    I was thinking that -- At the 0v point, you could dump the line to ground, continuing giving you 0v until the elapsed time, then closing the circuit, thus continuing the cycle.

    But, I think I had the wrong idea of what you wanted.

    I thought you wanted to delay the rise or fall after the 0v cross. But you want to trigger a pulse on a new circuit, not change the current one. I think.
     
  10. Cbaz

    Thread Starter New Member

    Oct 27, 2009
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    I hadnt considered the aproach you suggested retched. As long as I have a controlled delay of the pulse it doesnt matter wether I trigger a pulse on a new circuit or delay the rise or fall of the 0v on the current circuit. How would I modify my circuit to achieve what you suggested
     
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