Smartphone Camera Foot Switch Trigger

This foot trigger allows you to take hands-free pictures with your smartphone. I was inspired by this Instructable by Becky Stern, but because I don't have a camera, I made a version that works with my smartphone instead.

It uses an off-the-shelf foot switch from the hardware store and some cheap headset that came with my phone. A simple two-resistor circuit based on these Android specs makes the button act as a headset that sends a "Volume Up" signal to the phone, triggering the camera.

You will need the following materials :

• A foot switch
• 2 to 3 meters of two-stranded cable
• A headset with a built-in microphone
• A 2.2 k ohm resistor
• A 270 ohm resistor
• A piece of perfboard
• About 10 cm of wire

You will also need the following tools :

• A Phillips head screwdriver
• A small flathead screwdriver
• A soldering iron and some solder
• Wire cutters and wire stripper
• A multimeter
• A utility knife
• A round file
• Some CA glue
• A lighter or heat gun
• A drill with a 1.6 mm drill bit (optional)

Cut the earbuds at the base of the microphone and pry the case open with a small flat head screwdriver. Use the continuity setting of your multimeter to find the ground and microphone wires and desolder them from the circuit board. Trim the other wires.

Strip the ends of the two stranded cable and splice them to the headphone wires using a soldering iron and some solder. Use heat shrink tubing to protect the connection.

Solder the resistors to the perfboard according to the schematics, adding two wires for connecting the switch later. There is no polarity here, just make sure you solder the 2.2k resistor across the headset wires and the 270 resistor in series with the switch.

This circuit will have to fit inside the button casing, so try to make it as compact as you can (mine was just small enough to fit inside the case).

The holes of the perfboard were too small for the cable I used, so I made them larger using a 1.6 mm drill bit. If you don't have access to a drill, you could splice the cable to thinner wires instead.

When your circuit is complete, cut the perfboard to size by scoring it using a utility knife and snapping it. Solder the other end of the headset cable to the circuit.

The foot switch I used is the kind that stays on when you release the button. While this is ideal for a lamp, it won't work for a camera trigger, so I had to modify it to turn it into a temporary switch. Alternatively, you could use a regular foot pedal switch instead and skip this part.

Open the foot switch case using a Phillips head screwdriver and take the push button out. Using a small flathead screwdriver, pry open the push button (be careful not to stab your hand!).

The button is made of two parts that interlock with the case to keep the circuit closed when released (this is the same mechanism you would find in a retractable ball point pen. Check out this great video if you're curious about how it works)

Use CA glue to bond the two parts of the button together, and use a file to remove the teeth from the bottom part of the button. You will know you have removed enough material when the button can move up and down the hole freely.

Finally, put the push button back together. It should now spring all the way back up when you release it.

Connect the wires coming out of the circuit to the push button using the screw terminals and place the circuit inside the enclosure. Close the case, making sure no wire gets pinched, and screw it back together.

Make sure your camera app is set to trigger the shutter when the volume keys are pressed. Plug the headset jack in and press the button to snap a picture. Have fun!