Interface 3V SLR Timer Remote with 12V motor. Timer only switches .65V to gnd!

Discussion in 'The Projects Forum' started by Veetron, Sep 14, 2012.

  1. Veetron

    Thread Starter New Member

    Sep 2, 2012
    2
    0
    I bought a Bower SLR timer remote at Fry's for only $20. It can be programed to control the shutter with intervals and duration in increments of 1 second up to 99H,99M and 99S. I was hoping to use a 3V regulator to power the remote from my 12V battery. I would like to control a small 500 mA 12V pump. The problem is: the the control signal on the cable of the timer is only .65V until the event and then goes to .001V. I don't know how to work with that.
    Do I need an op Amp to step the voltage up and then invert it to work with TTL or CMOS gates? I never have learned how to bias transistors. I used to use relays for switching pumps but now I prefer N Channel MOSFETS. The remote has an LED that lights red or green and a small beeper so more voltage is available inside but I'd rather not have to open it for that. I was getting my reading by clipping the negative lead of my volt meter in the battery compartment and the positive lead on either the tip or center section of the 2.5mm stereo plug that would plug into a camera. I also don't have a clue as to how a camera works with this signal, obviously.
    If a transistor or JFET is the best way to go I would really appreciate a schematic with part values or ranges if possible. Thanks for any help.
     
  2. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    657
    I suspect that the output is a contact closure to ground (it might be in the form of an open drain n-channel MOSFET, or an open collector NPN). I believe the normal camera shutter control input requires a contact closure, and has an internal pullup resistor to a positive voltage inside the camera.
    Try adding a 10kohm resistor from the output of the remote to the power supply (e.g., 3V) of whatever logic system you are planning on interfacing with. The output should then switch from 0V to +3V, or whatever.
     
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