Introduction: Slave Flash From a Discarded Disposible Camera

This Instructable will show you how to turn the remains of a disposable camera into a slave flash for use with a DSLR camera or any camera with a hot shoe. It uses some off-the-shelf items that are relatively inexpensive and gives you the flexibility to have multiple flashes.

Step 1: Materials

Off-the-Shelf Stuff:  Tools: 
  • drill 
  • 3/8" drill bit 
  • needle nose pliers 
  • soldering iron 
  • utility knife 
  • small screw driver
  • a used disposible camera body with flash 
  • 4" of 22g insulated wire (and something to strip it with) 
  • 1/4" panel mount phone jack - solder

Step 2: Step 1: Initial Camera Disassembly

Remove the label from the back half of the body. This will allow access to the tab clips that hold the two halves together. Use the small screw driver so gently raise the tabs. Start with a tab on the top or bottom and work your way around the body. The back should come off and you should see the following, going from left to right; a AA battery on the far left side; the empty feeder spool next to the battery; a rectangular cavity with the lens at the center and another cylindrical cavity where the film canister was located. (Note! Depending on how aggressively your local photo processing clerk breaks into the camera body, the back half of the camera body may be missing the section over the film canister on the right). Keep the back panel. Toss the feeder spool.

Step 3: Step 2: Test Flash

There's no guarantee that the flash unit is still good or that the battery still has a charge (chances are good though).   There should be a button on the front to activate the flash charging circuit. Go ahead and press that. You should hear the whine of the capacitor charging and after a bit you should see the indicator LED light up on the back.  You should NOT have to hold the front button down.  If the capacitor won't charge without the button being held down, toss the camera and find another.  With the back off, you should see a small sprocket just under the view hole and above the rectangular cavity. The film advance wheel should spin easily since there is no film inside. When there is film in the camera and you advance the film with the wheel, the teeth on the edge of the film spin the small sprocket. This action resets the release button.   Since there’s no film in the camera now, go ahead and spin the small sprocket towards the right. You should feel the tension build and then the sprocket should lock once the release button is set. Now press the release button. You should see a flash. 

If you didn’t hear the whine, it’s most likely a bad battery. Replace the battery with a fresh one and repeat. If the flash doesn’t fire, toss the camera and get another one.

Step 4: Step 3: Continue Disassembly

Remove the battery and trigger the flash again. This will dissipate the charge in the capacitor (but not completely; BE CAREFUL). On the battery side of the body, there’s another catch. Carefully pull the front body section out and it should click off. This will free the internal frame and circuitry from the front panel. This is where you need to be careful. The contacts of the capacitor are exposed. If there is still a charge in the capacitor, you can get a nasty shock.

Set the internal frame and circuitry aside for later.

Step 5: Step 4: Modification of Body to Fit Jack

Different disposable cameras have different sized openings for the lens. Check the fit of your ¼” jack. If it fits without a problem, no further modification is necessary. Otherwise, you’ll need to enlarge the hole to 3/8” inch. Do this with a 3/8” drill bit and a drill. Check the fit of your jack again. It should be a nice fit now. Set aside for later.

Step 6: Step 5: the "guts" of the Disposable Camera

The internals of the disposable camera is made of two main pieces; the circuit board and the internal plastic frame. These two pieces need to be separated. To do this, the lens sub-assembly needs to be removed. There’s a clip on the left and right of the lens assembly to release. Underneath the lens sub-assembly is the shutter. What’s neat about the shutter is that it’s also the trigger for the flash. This is what we’re going to take advantage of for this Instructable.

Pop off the shutter and the tiny spring that’s attached to it. There’s a small clip that’s holding the circuit board to the internal frame. Pop this and separate the two pieces.

Step 7: Step 6: Modifcations to the Internal Frame

The ¼” jack extends from the front, thru the internal frame into the exposure cavity.   Room needs to be made allow this. From the back, use needle-nose pliers to remove the stepped pieces of plastic that line the exposure cavity. From the front, use a utility knife to remove the block that held the lens sub-assembly.   Check the ¼” jack for fit.

Step 8: Step 7: Wire It Up

Remove the upper plate that the small spring was attached to by using the soldering iron to push out the pins holding the plate to the circuit board. Using wire cutters, remove the last ¼” from the metal bar near the capacitor.
Solder a 2” piece of 22g wire to the hole where you removed the plate. Solder a second 2” piece of 22g wire on to metal bar. You can test the circuit now by installing the battery and pressing the button on the front. Again you should here the capacitor whine as it’s charging and after a few seconds the flash indicator light should turn on. Assuming your wires have bare ends, touch them together and the flash should trigger. Remove the battery and solder the other ends of the wires to the ¼” jack.

Step 9: Step 8: Reassembly

Seat the circuit board on the internal frame.   It won’t clip into place since we removed part of what holds it down in Step 6. Place the ¼” jack into the modified cavity. You might need to bend the connections in a little for a better fit. Replace the battery. This will help keep the circuit board and the internal frame together.
Replace the front cover while feeding the jack through the hole. Put the washer and nut on to the jack. You’ll be able to keep the jack aligned through the exposure cavity on the back. Lastly snap the back cover into place.

Step 10: Step 9: Take Pictures

Now get out there and take some pictures!!!

Other options that I've thought of but haven't implemented yet.
  1. Velcro patches on the receiver and flash body to keep them together.
  2. Adding one or more 1/4"-20 nuts to the body so the unit can be mounted on a tripod.