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What voltage are the bulbs in flashes, and are they rated in watts like normal bulbs? Also what about the smaller ones in compacts etc? For a secret project 
Outboard flash technical question!
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Canon Bob
Loves the Enemy
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Everything you always wanted to know about flash bulbs
http://www.flashbulbs.com/flashbulb_basics.htm
Bob
http://www.flashbulbs.com/flashbulb_basics.htm
Bob
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Maybe I got my terminology wrong- I meant the modern flashes- I thought they were long thin bulbs- not the old fashioned sort! I know most flashes take 4xAA batteries- 6V but is that the operating voltage of the bulb or are they stepped up?
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Search for xenon flash tube.
The technology is simple. The flash tube is filled with xenon gas.
There are two main terminals on the flash tube which you connect to a capacitor. The capacitor is charged to around 300V. Capacitances range from 1uF (micro farads) to several hundred uF (if you want to be blinded and showered in broken glass).
The xenon does not conduct until a high trigger voltage (several thousand volts) is applied to a third terminal on the tube. The third terminal does not make phyiscal contact with the gas, it just has to be close to the glass of the tube.
The trigger voltage comes from a step up transformer and it has a high voltage but very low power output.
Once the gas conducts, the capacitor dumps its charge and the gas gives the bright flash.
So, from the 6V you would step this up to charge a 300V capacitor, and use another small capacitor to dump a charge into the trigger transformer when you want the flash.
The tubes are rated by voltage, joules, and number of flashes.
So if you read 300V, 1 joule, 2000 flashes you can work out the capacitance from this:
E = 0.5 x c x V^2
That means the energy = half x capacitance x voltage squared.
Working backwards that gives a capacitance of 22 micro farads and you can expect the tube to last around 2000 flashes.
It's all good fun, but don't touch the terminals of a 22uF capacitor charged to 300V or you'll have a sore hand :bonk:
The technology is simple. The flash tube is filled with xenon gas.
There are two main terminals on the flash tube which you connect to a capacitor. The capacitor is charged to around 300V. Capacitances range from 1uF (micro farads) to several hundred uF (if you want to be blinded and showered in broken glass).
The xenon does not conduct until a high trigger voltage (several thousand volts) is applied to a third terminal on the tube. The third terminal does not make phyiscal contact with the gas, it just has to be close to the glass of the tube.
The trigger voltage comes from a step up transformer and it has a high voltage but very low power output.
Once the gas conducts, the capacitor dumps its charge and the gas gives the bright flash.
So, from the 6V you would step this up to charge a 300V capacitor, and use another small capacitor to dump a charge into the trigger transformer when you want the flash.
The tubes are rated by voltage, joules, and number of flashes.
So if you read 300V, 1 joule, 2000 flashes you can work out the capacitance from this:
E = 0.5 x c x V^2
That means the energy = half x capacitance x voltage squared.
Working backwards that gives a capacitance of 22 micro farads and you can expect the tube to last around 2000 flashes.
It's all good fun, but don't touch the terminals of a 22uF capacitor charged to 300V or you'll have a sore hand :bonk:
OP
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:bonk: of course xenon flash- don't know why I had forgotten that!
Thanks for the info- perfect sense.
Basically I'm looking to convert a cheap YN flash to 2 flashes, a bit like the canon MT-24EX, using the body of the off camera flash- (very basically) taking the top off and wiring in a pair of flash tubes on cords for my macro rig. The only thing I'm not sure about is whether or not I could wire 2 flashes in parrallel powered by the 1 main flash body, this is why I was considering using 2 smaller flashes from compacts but not sure how bright they are or voltages.
Thanks for the info- perfect sense.
Basically I'm looking to convert a cheap YN flash to 2 flashes, a bit like the canon MT-24EX, using the body of the off camera flash- (very basically) taking the top off and wiring in a pair of flash tubes on cords for my macro rig. The only thing I'm not sure about is whether or not I could wire 2 flashes in parrallel powered by the 1 main flash body, this is why I was considering using 2 smaller flashes from compacts but not sure how bright they are or voltages.