Adam writes -

One of my current projects is an Arduino powered camera trigger. I made one using my Arduino a laser pointer, and my digital camera. At first I thought it would be no big deal, but it took a little more effort because of the camera I was using. My Canon Powershot does not allow for remote shutter controll by default, but after a little inernet-vestigation I stumbled on the CHDK (Canon Hack Development Kit). After some firmware hacking and a couple components; I was up and running…

The Key is the CHDK firmware that allows the remote shutter trigger. The laser reflects off of a mirror onto the photoresistor. The photoresistor is being measured by Analog 0. When the beam is broken the Arduino runs through a series of high and low on digital 12 (with varying delay to account for the auto focus feature of the camera). This then triggers the camera to focus and take a picture.

Connecting the camera to the Arduino is done by modifying a mini USB cable. There is a USB remote cable page on the CHDK wiki with instructions/diagrams for making a Homebrew remote. So I just used that but left out the switch and battery because the Arduino would act as the switch power source. We’ll be using the +5V (red wire) and Ground (black wire) – (see below for picture of cable, code, and more pics)