Disposable Camera Flashes Live Again

Aiming to improve the image quality of the photos on his website, [Jean] needed an external flash unit.

ep-026-0280-960Say what you will about disposable cameras, but the fact that they were mass-produced, and are now nearly obsolete, means they are an absolute treasure trove of electronics components when you can buy them for dirt cheap. So [Jean] decided to turn a few of his disposable cameras into an external flash system for his DSLR (Translated).

He started by taking apart a Kodak digital camera and examining the circuit board. KEY1 enables the charging of the capacitor (the camera ON switch) and SW1 is located under the shutter-release.

Now all he had to do was replace SW1 with an electronic trigger from his DSLR.

To do this he built a custom circuit based on a triac and an optoisolator as shown below:


This isolation ensures the circuit does not get damaged from the capacitor when triggered. Finally he made a PCB that would fit in his DSLR’s hotshoe adapter to accept the 5V trigger — and that’s it!

Speaking of camera flashes, while you’re at it — why not build a $2 high-speed laser camera flash sensor for high-speed photography?

26 thoughts on “Disposable Camera Flashes Live Again

      1. We always took the batteries out. They were usually garbage anyways. We had to send the used cameras back for recycling but I used to keep the batteries. I didn’t know jack crap about electronics back then and it’s a shame. I had plenty of days where we were so slow that I could sit all day and not see a soul. I could have been salvaging components off of the boards.

    1. These are great toys for experimenting with little coilguns as well. Takes a bit of time, but you can get 300-400 Volts into a capacitor and throw washers and all sorts of things around with it.

  1. Glad the opto-isolator is prominent here. You can use the same circuit and wire in a PC-Sync cable to use with many older flashes as well. You must use isolation though because a lot of older flash units discharge 200+ V when they are set off. They used to sell safe flash devices for far too much that were an opto-isolator in a hot shoe.

    Hook this same circuit to a uC with a sound trigger or laser tripwire and you have a cheap high speed rig freeze stuff like droplets, glass breaking, etc.

  2. You can probably get those cameras free most places that accept them. I’ve gotten bags of them from walmart.

    I tried making a ring light out of them just by wiring them all up to a switch in parallel but they wouldn’t fire. Perhaps I should revisit it.

    1. Heck, I still have a handful of original 1940s/50s vintage GE flash bulbs. I’m almost afraid to try them out because I’m not 100% certain they haven’t been used and it would require a full rewire of the vintage flashgun.

      They are extremely bright though: The #22 bulb is rated at 63,000 lumen seconds with a peak somewhere around 5,000,000 or so lumens.

      Cave photographers often uses bulbs still because 1 or 2 can light a big area: https://www.ephotozine.com/article/a-shot-in-the-dark—guide-to-cave-photography-4680

      1. 63,000 Lm-s. Wow. That’s equivalent to around a 5000 W-s in xenon. That’s HUGE. A large camera-mount flash is 30 to 50 W-s. Typical stand-mount studio flashes are 150 to 400 W-s. A very large pack-based system is 2400 W-s and hard to carry single-handedly. I can see why cavers would prefer a lightweight flashbulb. (though a cave isn’t going anywhere: A 2000 lumen LED array would do that job in 30 seconds, and a 100 gram LiPoly can provide enough energy to do that 30 times).

  3. The writeup here implies the optoisolator schematic shown will work when plugged into the camera’s hotshoe. It won’t, because the hotshoe just closes a contact (or mosfet or triac or scr, depending on the camera). A hotshow provides no voltage on the X sync terminal, and won’t fire the optoisolator. It requires an outboard power supply. Jean’s web page does describe it more completely and shows he uses a 5V supply to fire the opto.

    However, it still won’t work properly on many cameras (i.e., more than once), because the quiescent current drawn by the opto’s LED keeps the camera’s SCR or TRIAC latched on until the 5V supply is removed. The easy fix is to use a 100K or more R1 and put a 0.1 uF cap across it: 100K won’t sustain enough current to latch the camera’s switch, but the 0.1 uF briefly lets through enough current to fire the opto’s triac.

    1. There is actually an additional circuit on the author’s page that triggers the optos from the hot shoe. The schematic above is the board he added to each flash to tie into a central board that triggers all the flashes.

  4. My company insurance requires a disposable camera in every vehicle for accident documentation. And they have to be replaced every couple of years, almost all of them never used. In addition to the flashes as described in OP, they all contain a normal 35mm film cartridge and a normal alkaline AA battery for the flash. They are generally discarded, not recycled, since most of them don’t go through the actual film development process (unless the vehicle is actually in an accident).

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