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Sizing wires for a photo flash

  1. Dec 24, 2014 #1
    Hi all. Please pardon the amateurish question! My hobby is constructing camera traps which I use to photograph wildlife, using small "point-and-shoot" compact cameras.

    Currently I am working on a project that involves removing the flash unit from the camera proper and installing it approximately two or three feet from the camera (via wires run in waterproof conduit). I'm looking for some advice on sizing wires running from the camera to the flash (I desoldered the flash unit, and connected the flash unit by soldering wires from the pins on the flash unit to the corresponding solder pads on the board. I know how to look up guides to sizing wire, but they rely on knowing the current, which is what stumps me.

    The flash is powered by a capacitor that charges to about 300V. The capacitor is 180 uF. There is a separate trigger circuit that produces very high voltage, but I believe this is integral to the flash unit. The trigger devices sends a jolt of high voltage through the xenon in the flash, causing it to ionize and short the capacitor.

    I already have a prototype unit built. I used some 16 gauge stranded wire I had laying around, (I decided overkill wouldn't hurt), and my prototype works. But 16 gauge wire isn't ideal; connections with camera components, and running wires out of the camera body are problematic.

    And what's the down side to undersized wires? Overheating? Damage to camera components?

    Merry Christmas to all, and thanks for reading!

  2. jcsd
  3. Dec 24, 2014 #2


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    Are the batteries in the flash unit or in the camera?
  4. Dec 25, 2014 #3


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    I'm assuming you are using the wires to supply the high voltage to the lamp. If not, it is a different problem.

    I'm answering without knowing all the facts, but I expect that if the flash works, the wires are OK. To really answer the question you need to know the amplitude of the current pulse being sent to the lamp. For that, a manufacturer spec sheet for the lamp might help.

    As the wires get smaller and smaller, the brightness of the flash will decrease if there is too much voltage drop. I doubt it will cause damage.

    Are you using the Canon hackers development kit?
  5. Dec 25, 2014 #4
    Thanks for the replies. Yes the batteries and the flash capacitor are on the camera. The wires run up to the flash unit and will carry the current from the flash capacitor to the flash unit. I've looked for specs on the flash without luck. Doesn't help that the camera is close to 10 years old and has been long discontinued. It's a Sony DSC S600 which has been a very popular camera for this stuff mostly because of the brightness of the flash.

    I'd like to drop down to at least 20 gauge wire. I guess I'll just try it. Nice to know that it's unlikely to damage anything.

    Canons aren't used much for "homebrew" trail camera, at least in point and shoots. (DSLR are another thing) I know people have tried the CHD kit (I believe it can be set to detect motion through the CCD). However, battery life is such an issue that they aren't practical. Canons are very difficult to "hack", that is solder wires onto power and shutter switches so that it can be controlled by a separate motion sensing board.
  6. Dec 25, 2014 #5


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    I have no experience with flash bulbs, so, that said, I'd be really surprised if 16 vs 20ga made a difference.

    The inductance of the long wires might make a difference, And I think you could reduce the inductance by twisting the wires together. Did you twist the wires in your initial effort? Others might know more about the peculiarities of flash bulbs and how the rise/fall time issues might affect them.

    Found these repair manuals
    http://www.depreyswildlife.com/Mods/Sony_S600/DSC600_3.pdf (see page sy-145 6/8)

    Flash unit part number is 479-571-11
  7. Dec 25, 2014 #6

    jim hardy

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    meBigGuy hit it ---
    if it flashes it's probably okay.

    Since the current pulse is brief you can operate the wire at current higher than its continuous rating.
    #22 is a convenient size, small enough to handle easily yet big enough to be stout in tension so not excessively fragile. It'll carry around 5 amps continuous in open air.

    The brief current pulse will have a sharp risetime so keep your wires close together - twist them or use lampcord. The idea is to avoid a big loop that'll have inductance.
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