Laser tripwire circuit help

Discussion in 'The Projects Forum' started by gtr675, Mar 19, 2011.

  1. gtr675

    Thread Starter New Member

    Mar 17, 2011
    Hi guys.

    I'm trying to build a basic tripwire circuit to trigger a camera flash.

    The attachment above is what i have come up with after browsing some older threads.

    I just need a little help to calculate the current and resistance where needed.

    The phototransistor i am using shows 5k resistance in average light and drops to 2.5k with the laser shining on it.
    A potentiometer would prob be a good idea also i guess.

    photo transistor-