People, I strongly urge you to only attempt this if you know what you are doing. There are high voltages involved in this (200-1000 Volts) And you can get shocked. I strongly advise the utmost caution while attempting this. While the shock will not really harm you, it is extremely painful. BE CAREFUL.
First, The Materials.
A Disposable Camera (2-5 Dollars)
An Older 3.5 mm Stereo Jack (Free - 1 Dollar, Electronic Goldmine - 6 Ft. Cable )
A SCR (Silicon Controlled Rectifier, Like A Transistor) (Digi-Key, Digi-Key #EC103D-ND , 39 Cents)
Electret microphone (Just a normal microphone, WITH A STEREO 3.5 MM JACK) (Free)
A Camera Capable of Prolonged Exposures or a bulb "B" Exposure Setting (AKA A newer SLR camera)
A Multimeter with a high-voltage DC option.
The Steps
Take apart the disposable camera (CAREFULLY) So that the only parts remaining are the circuit board and the battery. Remove the battery. Short the capacitor. ( The capacitor is the cylindrical thing. It has two leads. Put a piece of wire or metal pliers across the two leads to short it. It might make a loud sound. And smoke. This is normal. )You need to solder wires to two places. These wires trip the flash. Sometimes the places you need to solder this are obscure in location, but are sometimes obvious. I recommend going to your local CVS and grabbing one of their CVS brand cameras (AKA the cheapest). When you take it apart, there should be two leads that are made of thin copper. They will be very close, and flexible. If you touch them, you will receive a small, short shock. Most of the time. You need to solder one wire to each. Then find the flash ready switch. This is under the button that charges the flash. It should be easy to find.
Next, Get that SCR out of the little baggy it came in. Face it so the curved edge is on the table and the leads are facing toward you. Remember those two wires you soldered to the camera? Use the multimeter to find which one is positive and negative. You need to put the battery in to do this. It should charge. If it doesn't, check the connection you made with the little charging switch you made. After it charges and you know which lead is positive and negative, short the capacitor AFTER taking out the battery. You need to solder the positive lead to the right lead of the SCR, and the negative lead to the left lead of the SCR.
Next, cut off one end of that nice cable. There should be three leads. If you need help with this part, contact me. There should be a red, black, and white wire inside the cable. Solder the black wire to the left lead of the SCR. Solder the red and white wires to the center lead of the SCR. You are very close to being done!
Next, go on to your computer. Plug in that microphone into the microphone port. Change the master volume so that when you talk into the microphone, you can hear your self over the computers speakers. This can be done by turning the microphone volume all the way up and Un-muting it (If it was muted). Next, plug in your cable (That goes to the camera) to the speaker jack. Put in the battery. If all goes well, if you clap or something like that next to the microphone, the flash will go off. If it doesn't, I cannot help you. You will need to troubleshoot on your own.
For the fun part. Turn off the lights. Put in the battery. Set your camera to "B" or a shutter exposure of about 5-10 seconds. If possible, set the F number to 4.5 and the ISO to 100.
Open the shutter, and take your picture!
PM me if you have issues. With the camera.
