One of the favorite devices of the ¨free energy¨ experimenters is the disposable camera flash. These circuits can be obtained for free from the local stores that process the disposable camera pictures (I got mine from Rite-Aid). However if you don´t wan to ask your local store for some free ones, you can buy them from Electronic Goldmine (they call it a strobe unit for some reason). I asked for some at a Rite-Aid store and got more than a half dozen, so it would be no surprise if Electronic Goldmine doesn´t sell many of them.
This flash unit has three sections:
DC-DC Converter The battery, DC to DC converter and storage capacitor make up the first section. The battery is usually a single AA cell. The user pushes a pushbutton switch which connects the battery to the circuit, and a neon light lights when the flash is ready. The DC to DC converter uses a high current, very low Vce(sat) transistor to drive a tiny transformer to step up the voltage, and a few more parts, maybe a transistor or two to limit the voltage. A diode rectifier and 120 to 160 microfarad 350 volt electrolytic capacitor to rectify and store the flash energy.
Trigger Circuit Some of the high voltage is used to charge a small capacitor, which is connected to a pair of switch contacts. The contacts discharge the small capacitor through a high voltage trigger coil, which puts out a few thousand volt pulse to the tube.
Flash Tube The Xenon flash tube is connected across the electrolytic capacitor so it has a few hundred volts across it, which can give you a wicked shock. DANGER – When you are going to play around with this, you should discharge the electrolytic with a 100k resistor before you fiddle with it. The flash tube also has the trigger electrode, which gets the high voltage pulse from the trigger circuit- another source of a nasty shock.
Some experimenters connect a CFL bulb (only the bulb part, minus the base) to the output of the DC to DC converter. Other experimenters connect the converter´s output to strings of LED Xmas tree lights. One experimenter tried to make a strobe out of the xenon flash unit. For a strobe, the DC to DC converter takes too long to build up enough energy in the storage capacitor, so he rectified the AC line voltage to get about 340 volts. Then he added a circuit to continuously trigger the trigger circuit – may have been a 555 timer chip. The circuit worked, but the amount of energy in the storage capacitor was so high and it made the xenon tube so hot that it melted the plastic reflector. He had to change the storage capacitor to a few microfarads to lower the stored energy and stop the plastic from melting.
You can do a web search and find many projects using these free, fun-to-use disposable flash units. Youtube has a number of them. Also try Instructables.
Back to experimenting…