lowering the voltage of camera flash circuits?

I have some camera boards on eBay and someone asked me if there was a way to lower the voltage with a resistor, I would imagine that a resistor wouldn't work, but is there a way to do so, maybe use a different capacitor? 

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A single resistor on the output of the flash board will not cause the cap to be charged to a lower voltage. It will only increase the time constant of the circuit, essentially causing the cap to take longer to charge, but the final voltage on the cap will reach the same value it did before.

I assume that you want to use them to charge a capacitor to a lower voltage. This could be done by putting a voltage divider on the output, but there would be a few things to watch out for.

If you are not familiar with it , a voltage divider is just two resistors in series. When connected between the high voltage output of the charger and ground, it will divide the voltage down to a lower value. The lower voltage is obtained where the two resistors are connected toghether. Search on voltage dividers and ohms law if you are not already familiar with them.

The resistors used to make the voltage divider must be able to handle to the power that will be dissipated in them, and they must be able to withstand the voltage across them. Use ohms law to determine the voltage across each resistor and the maximum power dissipated in each before seleting the parts to build the circuit. Camera flash boards can produce output voltage of hundreds of volts, and common resistors are most likely not rated for that high a voltage. Either get resistors rated high enough, or use multiple lower rated resistors in series.

+1!
Not knowing the circuit, I can't give a proper solution, but I'd like to know how the circuit knows to stop charging ?

Steve
Jimmy Proton (author)  steveastrouk6 years ago
thats a good question.
Pick out the circuit, and you MIGHT be able to limit the voltage that way.