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  1. #21
    Ralph Javins's Avatar
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    Quote Originally Posted by Wolfeye View Post
    The voltage "warnings" people often tout aren't the whole story. The real number you need is power, which is voltage times current. if you put 5v in a circuit with 1 ohm resistance you get 5amps of current. 5amps times 5v = 25watts of power. Likewise, if you put 300v in a circuit with 1 ohm resistance you get 300amps, which means 90000watts of power. If a flash actually was putting that much power through ANY electronic circuit it would melt. The current simply isn't as high for the high-voltage flashes.
    Good morning;

    Wolfeye's comment is instructive, but not fully imformative. He does allude to one of the main qualities of the equipment being discussed; their current handling capability, which is roughly related to the physical size of parts involved. Another quality of interest here is the what some might call the "insulation" value for the parts inside. This also might be thought of as the "physical strength" to resist the voltage or force being applied to the camera flash control circuit from the electronic flash firing circuitry. If you apply sufficient force or voltage, you can "crack" the part. If you have sufficient force and a low impedance source with sufficient capacity to provide the energy or power, you can "crack" the part and displace the little pieces just a little, or a whole bunch depending on how much power (force and energy) you have applied. In terms of what we might see and hear, did it go "pszzt" with a small blue spark or perhaps even a blue flash, or did it go "KA-POW!!" with a great flash, some smoke, and a tingling sensation or numbness in the hand that was holding it?

    Want another analogy? Did you tap on it with an 8 ounce ballpeen hammer, or did you smack it with a 10 pound sledge hammer? In both cases, you will break it. In the second case, not only will you break it, you will also smash the pieces.

    The warnings about the possible damage to the late model camera flash circuitry are not just idle threats. There is a real danger to the camera where the circuitry inside the camera now merely must meet the ISO standard of being able to work with a flash firing circuit voltage of no more than 24 VDC. (We can talk about how this was interpreted.) The Wien SafeSync device, or equivalent, will move the high voltage insulation requirement for the actual flash circuit switch, from inside your camera out to a device that is much cheaper and easier to replace if required, than it is to have your camera repaired.
    Enjoy;

    Ralph Javins, Latte Land, Washington

    When they ask you; "How many Mega Pixels you got in your camera?"
    just tell them; "I use activated silver bromide crystals tor my image storage media."

  2. #22
    Steve Smith's Avatar
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    Quote Originally Posted by Wolfeye View Post
    The voltage "warnings" people often tout aren't the whole story. The real number you need is power, which is voltage times current. if you put 5v in a circuit with 1 ohm resistance you get 5amps of current. 5amps times 5v = 25watts of power. Likewise, if you put 300v in a circuit with 1 ohm resistance you get 300amps, which means 90000watts of power. If a flash actually was putting that much power through ANY electronic circuit it would melt. The current simply isn't as high for the high-voltage flashes.
    Mot really relevant for a flash. A fairly basic flash trigger circuit consists of a small value capacitor which is charged via a high value resistor connected to the main high voltage capacitor. The camera's shutter contacts discharge this small capacitor into the trigger transformer which causes the flash tube to conduct. The flash tube is connected permanently to the high voltage supply but will not conduct until triggered. The high current drawn by the flash tube does not pass through the camera's shutter contacts or electronic equivalent.

    I personally think the low trigger voltage requirement stated by some manufacturers of modern cameras to be a bit of a myth for the purpose of selling new 'compatible' equipment.


    Steve.
    "People who say things won't work are a dime a dozen. People who figure out how to make things work are worth a fortune" - Dave Rat.

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