Aiming to improve the image quality of the photos on his website, [Jean] needed an external flash unit.
Say 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?
Great idea, those old cameras can be had by the dozen at any Goodwill for next to nothing.
I like to get unused film out of them and then develop it myself. Mysteries to behold.
“Unused” film would yield a blank photo. Mystery solved. :)
Never tried myself, but apparently unexposed film when developed becomes a good IR filter.
Once upon a time, photo labs would give empty cameras away for the asking. Usually the batteries had a fair amount of charge too.
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.
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.
True that, I used to shock my classmates with 2 wires straight on the capacitor… it gave some nice jolts.
Was gonna say — take care when taking these apart. That cap can hold a couple hundred volts for at least a few minutes in my experience. (Estimated the voltage by how loud it made me yelp.)
I have an arc divot on one of my screwdrivers from decades ago by a camera flash.
If you find places that process the cameras they will usually give you as many camera bodies as you want. They just throw them away.
So this guy is making photo’s for his website using an EOS300? Oldscool!
Actually it was just a “placeholder” camera to show how my ghetto flash connectors fits into the camera shoe :)
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.
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.
Outfits like Electronics Goldmine have the flash boards for cheap sometimes. I bought a couple dozen for $0.25/each a couple of years ago.
Hmmm.. That’s not what I was picturing after reading the title. Those disposable cameras were never really disposable. The drug store replaced the film, repackaged and resold them. That’s not a disposable flash.
This is a disposable flash! http://www.melicontreras.com/c/general/page/15/
Finding that picture brought back memories I didn’t even know I had. Ebay time?
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
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).
So they’re good for more then just frying RFID tags.
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.
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.
*SLR, not DSLR :)
Hackaday will contact you before posting any future articles so you can proofread them.
What do you suppose he took the picture of his SLR with?
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).