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Discussion in 'Beginner Electronics' started by Henry, Dec 27, 2005.

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  1. Henry

    Henry Guest

    Sorry that I am being such an annoyance, but I have another question. I dont
    want anyone to go through the trouble of providing an entire circuit. In
    fact I want to do it myself. I just wanted to be pointed in the right
    directions. What parts do I research, etc.

    Anyway, here is the problem. I want to electronically trigger a photo flash
    of unknown trigger voltage. The flash provides the voltage. The circuit
    simply needs closed to fire the flash. But here is the trick. Photo flashes,
    especially older ones, have a wide range of trigger circuit voltages. At the
    low end it could be only 3.5v. On the high end it could be 300v. I have 3
    flash units. (3.5v, 15v, and 55v) Although I read that there are a few old
    units that go 100v and higher. Much above 5v can be death to a modern
    electronic camera. So I want to make a circuit such that I can use any of
    mine, and maybe other, flash unit with a electronic camera. (Either mine or
    a friend's.)

    So, what kinds of componets do I research that can give me the ability to
    trigger a flash with a range of 3.5 to, say, 100v? I have done a search and
    found high voltage transistors that can handle 200v (collector to emitter)
    but still only need 5v at the base. Someone has mentioned looking into
    something called an SCR. That same person suggested an opto-isolator for
    best possible protection of the camera. What about a voltage regulator? (I
    might be using someone else's $1000+ digital camera, so I want to be extra
    carefull. Last thing I want to do is to return to them a fried camera.)

    I have found sites discussing the theory of some of these components, but
    they dont really give the practicle trade-offs as to when you might want to
    use one verses another. Again, I am not looking for an exact circuit, just
    an idea what to best spend my energy researching.

    Thanks in advance,
  2. Dan Hollands

    Dan Hollands Guest


    Use an optical isolator


    choose one with Vceo greater than 200V

    It isolates your trigger signal from the flash and if you connect the plus
    wire from the flash to the collector and the minus wire from the flash to
    the emitter it should act like a switch which closes when you put current
    thru the optocal isolator diode


    Dan Hollands
    1120 S Creek Dr
    Webster NY 14580
  3. Henry

    Henry Guest

    That simple huh? ANd I was getting ready for this complex circuit.

  4. Decide which voltage flash unit you would like to use first. Then go from
  5. JeffM

    JeffM Guest

  6. Henry

    Henry Guest

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