Mk II EOS Camera Timer
19/09/2011 - easily constructed electronic timer which provides exposure times from 1sec to 10 minutes in intervals of 15sec at the short end (14 in the first instance) through 2 minutes. Battery operated and fits on hot-shoe of camera; uses the jack plug into camera for control. Unit provides indication through the LED of time remaining (flash rate) and battery condition (tri-colour LED -> Green, Amber Red). Works a treat and quick to set up. The second potentiometer provides 16 intervals between exposures from 4 through to 19 secs - useful for PE measurement when used in conjunction with 1sec exposure setting. The heart of the unit is a PIC16F716 which has been appropriately programmed. Camera switching is via a miniature relay; total current consumption is 20mA max, which could be reduced by removing the relay and providing an electronic switch using an open collector transistor (NPN), or open drain N-channel FET. On-camera design inspired by Pat Kuehn - a fellow astro-photographer who has an interest in programmable electronics.