##Introduction## To get the cameras to trigger simultaneously, we chose to trigger them via USB using a feature of the CHDK. Dual camera 555 trigger ##Assembling the 555 circuit## * Pretty good instructions come in the 555 timer package * Potentiometer confusion * Stripping and attaching the USB cables Dual camera 555 trigger ![Battery "hack"](https://publiclab.org/sites/default/files/imagecache/default/IMG_0033.JPG) ##Connecting the batteries##
5 coin cell batteries + 1 screw fit in the holder Place them inside one by one Four should fit snugly and securely
* 2 different batteries needed: 12v and 5.5v or more * Fitting cell batteries into N-type holder (hack) * Attaching to the 555 timer (extra wire) ##Splicing USB cables## Image dump:
Snip the USB cable to at least 8 inches long Separate out the wires from the wrapping
Snip off all but red and black; strip off their wrapping