Recently I’ve been thinking to make a photographic Triptych. I wanted to show the stages of a balloon being inflated and then popped. In order to capture the pop and expression of the person while popping the ballon I will have to pop lots of balloons. So I got the idea of using a sound trigger . Arduino would be the initial thought but I said it can be done easier. There are so many light switches that respond to claps. After some researche on the web I found an electronic kit tha does something similar to what wnat. It’s an audio device used as music visualiser , with 5 LEDs that flash brighter with higher volume. That’s an excelent start , cause instead of the LEDs I can use a relay. But to make sure it’s electronically isolated from the camera trigger circuit I used a octocoupler or optoisolator.

List of what I used in for the audio trigger

• Audio LED flasher kit
• TLP222G
• 100Ohm resistor
• Shutter Release cable for camera ( MC-DC2 for my Nikon)

The main circuit board is the LED flasher

This is called Sound Activated High Brightness Blue LED Flasher on eBay. I bought a diy kit which requires soldering because I don’t us ethe LEDs, but instead I removed the electric traces from the PCB between the LEDs and soldered the TLP222G with a 100Ohm resitor in series .

Modified Circuit

Below you can see the intention of the modified circuit. the output of the octo-isolator ,pins 3 and 4 are connected to the wires from the shutter cable . For Nikon it seems you need to activate prefocus first , so the focus wire(white) of the MCD2 cable is shorted to ground(black wire) and attached to pin 3 and the shutter wire(red) attached to pin 4. My camera is set to back button focus , so there’s no focus action when using this.

Here’s the thing in action: