Capturing the most fleeting of moments—like the droplets formed by a splash of water or the ripping plastic from an exploding balloon—used to be expensive propositions. Fancy photo strobes with special voice- or sound-activated switches (called VOX) costing hundreds of dollars were the equipment of choice for high-speed photographers. Not so, anymore. By tapping into the powerful tools housed inside disposable flash cameras, you can build your own high-speed photography system for under $30.
Warning: Before you start working with the flash mechanism from a disposable camera, remove the battery and make sure that the onboard storage capacitor is completely discharged (hold a pair of insulated pliers across the + and - flash terminals and manually trigger the flash).
How to Build a DIY High-Speed Flash System
(1) Disposable flash camera (The Electronic Goldmine #G16329; $1.29 or Fuji Photo Film QuickSnap; $5.99)
(1) Silicon Controlled Rectifier (SCR) sensitive gate 0.8A 400V (Digi-Key #EC103D-ND; .39)
(1) 3.5mm stereo cable (The Electronic Goldmine #G15449; .99)
(1) Cassette tape recorder (scavenged or Memorex MB1055 @ Target; $19.99)
(1) Electret microphone (scavenged or All Electronics #MIKE-75; $2.50)
(2) AA & (2) AAA alkaline batteries
Camera capable of B (bulb) or prolonged (> 2 seconds) exposures
Step 1. The Anatomy of a Flasher.
Remove all of the exterior plastic, film advance system, and shutter assembly from the disposable flash camera. Locate the + and - flash terminals. These terminals are located near the shutter. Use a voltage meter for identifying which terminal is positive (+) and which one is negative (-). Some cameras (e.g., Fuji QuickSnap, as pictured) might require the flash on/off switch to be soldered in the on position.
Step 2. Becoming Flash Trigger-Happy
Snip off one jack of the 3.5mm stereo cable. Prep the snipped end exposing the red, white, and black wires. Solder the cathode pin of the SCR to the negative (-) flash terminal and solder the anode pin of the SCR to the positive (+) flash terminal. Solder the red and white wires from the 3.5mm stereo cable to the SCRs gate pin. Finally, solder the stereo cables black wire to the negative (-) flash terminal (along with the SCR cathode pin).
Step 3. Void the Cassette Recorders Warranty
Remove the cassette tape door from the cassette recorder. Make sure that you have clear and easy access to the cassette recorders write-protection button. This is a small movable finger opposite the record head that determines whether or not a cassette tape can be recorded. This button must be depressed to turn the cassette recorder on in record mode. You will use the record mode for gathering sound and amplifying it enough for triggering the flash.
Step 4. Lights, Cameras, High-Speed Action
Find a darkened location for experimenting with high-speed photography—an area completely devoid of ambient lighting. Mount your camera on a tripod, set the shutter for a bulb or B exposure. Cameras that can deliver timed 1-4 second exposures can also work.
Insert fresh batteries into the disposable flash camera. Plug an inexpensive electret microphone into the recorders MIC input. Plug the jack of the 3.5mm stereo cable into the PHONE output. Hold down the recorders write-protection button and press the recorders red RECORD button. The flash should begin charging. [NOTE: some disposable cameras might require you to depress a flash activation button.] When the amber ready light glows steadily on the back of the disposable camera, the flash is ready to be triggered by sound.
Kill the lights, hold the flash trigger near your subject, open the cameras shutter, and record some high-speed event that is triggered by its noise. Like the pop of a balloon, the kerplunk of water, or the smack of a head slap. Take your pick and take some pix.