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Circuit help: switching a load only at peak of AC mains

Discussion in 'Electronic Basics' started by JB, Sep 17, 2013.

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  1. JB

    JB Guest

    I have a series of measurements to make of the inrush current of a range of
    LED drivers and electronic ballasts. Is there a simple way of ensuring that
    the load is always switched on at the peak of the mains cycle? I'll probably
    use a substantial relay or thyristor to do the actual switching. This is for
    a single phase 230V 50Hz supply.
    I have done zero crossing triggers for switching loads but never peak! My
    Google mojo seems to have deserted me on this one. Any help much
    appreciated.
    JB
     
  2. Phil Allison

    Phil Allison Guest

    "JB"
    ** Well, a zero crossing detector followed by a 5 m/S delay will do it.

    I know someone with exactly the same task as yours and he used a PIC
    programmed to get both zero and peak switching of a triac - which he also
    bypassed with a hefty relay operated simultaneously to eliminate glitches
    associated with some of the loads encountered.



    .... Phil
     
  3. Can it be that difficult to make a 90 degrees shifted sine and switch on the
    zero crossing of it?

    petrus bitbyter
     
  4. Timing it is easy. But if it is part of a regulation scheme the thyristor
    will also have be capable of being turned off while carrying full current.
    What's the term for this - commutation?

    Or is this a problem of designing a solid state relay that remains on for
    one or more cycles, one where it is allowed for the thyristor to turn off
    on its own at the next zero crossing following the arrival of the "off"
    signal?

    George
     
  5. Daniel Pitts

    Daniel Pitts Guest

    Can you just give it the right voltage as a DC pulse to perform your
    measurements? That seems like an easier task to me.
     
  6. Daniel Pitts

    Daniel Pitts Guest

    Can you just give it the right voltage as a DC pulse to perform your
    measurements? That seems like an easier task to me.
     
  7. Phil Allison

    Phil Allison Guest

    "Daniel is the Pitts"

    ** So stupid, it's actually funny.




    .... Phil
     
  8. The OP only asks for switching on so far. There are dozens of SSRs for sale
    designed for switching on at zero crossing. So you use the shifted sine to
    switch on the not-shifted. As for switching off GTO devices can be
    considered. Common SSRs switch off at the zero crossing of the load current.

    petrus bitbyter
     
  9. Phil Allison

    Phil Allison Guest

    "petrus bitbyter"
    ** The loads being considered are essentially off line switchers (
    PS ) - so the current draw falls to near zero just after each AC voltage
    peak, requiring the SSR to be re-triggered every half cycle at the next
    peak.

    Or, just drive the LED on continually until you want the SSR it to
    commutate off.



    ..... Phil
     
  10. Daniel Pitts

    Daniel Pitts Guest

    Why don't you enlighten rather than belittle?
    You are? Well, I'll try not to laugh at you.

    If the OP needs to make a measurement of the inrush current on the LED
    drivers and ballasts, why not simulate the conditions the easiest way
    possible?
     
  11. Phil Allison

    Phil Allison Guest

    "Daniel Pitts" = "Daniel is the Pitts"

    ** No-one can teach a pig to sing.

    And you are another PITA fucking troll.

    Piss off.
     
  12. Daniel Pitts

    Daniel Pitts Guest

    Lol, I think you were looking in a mirror and saw the troll.

    *plonk*
     
  13. Phil Allison

    Phil Allison Guest

    "Daniel Pitts" = "Daniel is the Pitts"


    ** **** you - pig brain.
     
  14. Jasen Betts

    Jasen Betts Guest

    use a dimmer and adjust it while observing?
     
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