T3D Re: Diodes in joined cable releases

[Bob Wier <wier@xxxxxxxxxxxxxxxxx>]

|I am forwarding this question from Al Sieg:
|
|>I shoot a lot with two SLR's using a cable realse that has been
|>modified to provide a contact with both cameras.  Once in a while strange
|>things happen when using this method.  I was told that I should put a diode in
|>the circuit to prevent cross talk.  Do you have information about this or can
|>you lead me to the right source?  Thanks for any help you can give.
|
|Any help will be appreciated!
|
|-- George Themelis

Right offhand, I'd think you'd *want* crosstalk to make sure that both cameras fired
simultaneously. However, there are two main parameters - if you use a small signal
silicon diode, you'll have a forward voltage drop of about .7 volts. This may or may
not be a problem, depending the voltage necessary to fire the shutter.

The second consideration is the way the circuit function - does it send a positve
going pulse to trigger - or possibly a negative pulse? Or alternately does it *normally*
have a voltage present, and does it fire the shutter by interrupting the voltage (I'd be
surprised if so, because of the battery drain problem).

I used a similar circuit in my car to sound a buzzer whenever either of my turn inticators
(left or right) were going - the built in clicker was too soft and I'd end up driving down the
road with one on for miles (I hate people who do that!). So I stuck in a buzzer, but couldn't
just wire the lines together since one light would flash the other unless they were
isolated...

THANKS

   ====== wier@xxxxxxxxxxxxxxxxx ======
  7:39 PM Thursday, May 28, 1998
   keeper of the Photo-3d and Overland-Trails
       mailing lists and other stuff
     (currently in Ouray, Colorado)



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