Step 1: Materials & tools
(1) Hands-free cell phone kit
IMPORTANT: The DSLRs take a 3/32" stereo plug. See the picture for details.
(2) Momentary buttons (two colors)
(1) Mini micro switch
(1) Enclosure, for me a wonderfully ironic 35mm film canister
Drill & bits
Soldering iron and solder
Wire stripping tools
Mad Skillz (which you have, because you're cool enough to find this)
Step 2: Break open the mic
You may not get the same model kit, so some experimentation is required.
Inside the microphone box was a tiny circuit board hooked to 4 wires. I plugged in the kit to my camera for testing. Don't worry, there' s no current in these wires. I took my knife and shorted various combinations and observed the results. I found that two are ground wires, and the other two have functions:
By connecting the Red to a ground, the camera focused. Wonderful news.
We will now make button to do this work for us.
Step 3: Solder up the connections
Step 4: Make an enclosure
Step 5: Mount stuff
Step 6: Test and troubleshoot
But if they don't work, don't fret. Be very patient, take it apart, and test your soldering again. That's always where it fails.
Also when you coil all the extra cable into the canister, use a bit of tape to keep the complicated end of your project inside the can.
Below is a picture of the shutter release in action!