According to Wikipedia:

An intervalometer is a device which counts intervals of time. (Other names include interval meter and interval timer). Such devices commonly are used to signal, in accurate time intervals, the operation of some other device. For instance, an intervalometer might activate something every 30 seconds.

In photography, intervalometers are used to trigger exposures. This is often done for a time-lapse series. It may also be used to take, or begin taking, picture(s) after a set delay.

Since I want to automate the entire Pan Tilt head; having the camera take Photos automatically at intervals would be helpful, online is Sebastian Setz’s Arduino Multi Camera IR Control, which is a useful set of codes for controlling Canon, Nikon, Olympus, Pentax, Sony or Minolta cameras with an IR sensor. however this wont always work as some cameras don’t have IR Sensors.

The Parts list for the IR realise system is

  1. Arduino
  2. IR LED
  3. Resistor

As such it requires access to only one IO pin.

For Cameras without IR remote shutter realise; I am thinking about mounting a servo which will physically articulate the shutter realise button. this servo could be mounted off the Hot Shoe [note Image of Zoom H1 Holder for Camcorder/DSLR] or using 15mm system (I can build the entire head round the 15 mm system) There are a number of cool parts that can be made to work with the Photography/Videoography  industry standard 15mm tube system that can be printed.