View Full Version : Stupid electric shutter question

26-Oct-2005, 11:48
Got into the big box of stuff and pulled out two electric shutters. One is from a long-roll MF camera, the other from a military lens.

How in the world can I find out what kind of juice they need? I have an ohm meter, but that's all. Can I just try a 9V battery, then a 12V motorcycle battery, then two 12V batteries in series? Will DC hurt an AC circuit?

Help me before I let the smoke out of these things. :)

Bob Salomon
26-Oct-2005, 13:10
many, if not most, aerial cameras ran on 24V. Is the military one from an aerial camera?

Conrad Hoffman
26-Oct-2005, 13:16
I can't guarantee you won't burn 'em up, but here's what I'd do. They're probably DC. Measure the resistance and use ohms law to pick a voltage that doesn't dissipate more than a watt or two. That should be a safe value for very short term operation. Say the resistance is 96 ohms and you want 1.5 watts. The square root of 96 times 1.5 is 12 volts. See if the thing works at 12V (or whatever you calculate). Only power it for a few seconds. Actually, I'd creep up on it from a lower voltage. Here's the problem. Most solenoid coils can handle large amounts of power for very brief periods. Manufacturers often hit them with a short high voltage pulse to get them to open quickly, then back off to a much lower voltage to hold the shutter open. The voltage that you find will run the shutter may be too high for continuous operation. Or not. It just depends on the shutter. Many decades ago I worked for a division of Ilex that built the electronic version of their shutter, so my knowledge may be pretty old. Now, I'm assuming you are driving the shutter directly, not trying to power some control circuit. If that's the case, you'll need to examine the circuit and try to devine the voltage from IC specs, and some knowledge of the circuit design.

26-Oct-2005, 14:07
Thanks for asking, Bob. I forgot that part. Here is a picture of the business side.

elearning.winona.edu/staff_o/jjs/shutter.jpg (http://elearning.winona.edu/staff_o/jjs/shutter.jpg)

It is probably an aerial camera. It has the four marking lamps that print the "+" marks on the film at time of exposure. But then it gets strange: it was built to use conventional 8x10 sheet-film holders, and has a regular ground glass back that looks very 'Kodak' like. Also note the pull wire just right of the motor. It manually opens the shutter.

Conrad - thanks. That's just what I need to know. Very helpfull, indeed. DC it is, and I"ll creep up to 24 volts.

Ernest Purdum
26-Oct-2005, 18:59
If you don't mind doing a little disassembly, you might find a part number on the rotary solenoid that would enable the maker to give you ratings. Rotary solenoids are a specialty of Ledex and the last I knew they were very much in business.

26-Oct-2005, 21:02
Ernest, yes it is a Ledex. "Ledex Inc. Dayton Ohio" is stamped on it, but besides part of a peel-off serial number, no other markings. I didn't know they were still around. I'll surf 'em out!