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Thread: Electronic button pusher?

  1. #1

    Electronic button pusher?

    Sort of along the lines of Nicolai's thread, but simpler: What kind of device would push a shutter button down? The original thought for this was to wire some sort of electronic cable release for the Holga. I can imagine how a small motor inside the Holga would suffice, but I'm still curious about what component moves in and out, in just one direction.

  2. #2

    Electronic button pusher?

    A solenoid. Some push, some pull, some do both. Check http://www.jameco.com for examples (search on solenoid).

  3. #3

    Electronic button pusher?

    If you're going to hold it for any length of time, however, you need to reduce the voltage to the solenoid to avoid damage to the coil from overheating. I don't recall the amount needed; some solenoids will actually give "pull-in" and "hold-in" current requirements, but it's pretty uncommon.

    Also, a solenoid with any significant power will tend to be big, heavy, and need a biggish battery.

    Simpler would be a small geared motor with a cam on it; you could even put in a microswitch to operate off the opposite side of the cam so it *stops* when the button is fully depressed, until you start it with a second switch (that bypasses the cutoff switch). Or you could use the bypass directly for a "momentary" actuation, of course. The motor and some of the gears out of a P&S motor drive would be just about right for this, I'd think...

  4. #4

    Electronic button pusher?

    Electric shutter drive technique is typically apply 4 x rated voltage for about 5-10 electrical time constants to open faster than normal, then reduce to 1/2 the rated voltage to hold open.

    Sounds complicated, but once someone figures out the math for a given solenoid, it's just applying the voltage thru an RC network carefully selected. Somewhere, in that big set of boxes o projects I have a schematic for an Ilex controller that I figured this out for, along with measuring the L & R of the solenoid. Somewhere I have data for Ilex (synchro) electronic shutters too...found the company that made their solenoids, got the guy to talk and between the time he said hello and eventually realizing he talked too much, I got some good info :O).

    On the other hand, if you aren't trying to achieve the maximum speed capability, the rated voltage should be fine unless it has a duty cycle limit.

    I will find this info someday in the next couple months...maneuverability in the basement has been reduced to near zero.

    Pull-in voltage and holding current comes to mind.

  5. #5

    Electronic button pusher?

    In the spirit of avoiding simplicity, which might inhibit the development of variations on a theme, consider the following 'overkill' device & circuit. Tnen we can simplify.

    It's got power, levitation, AND self-wound coils, so it has the raw materials to move a shutter or maybe even an auto-focus view camera!

    http://www.amasci.com/maglev/magschem.html
    http://amasci.com/maglev/levgif.html

  6. #6

    Electronic button pusher?

    The few electric shutters I've seen don't actually lock the solenoid to hold the shutter open. Instead they either have two solenoids, one to open the shutter and one to close it, or they have some sort of over-center arrangement where one push (or pull) from the solenoid opens the shutter, and the next one closes it.

    An example of the former is here: http://www.surplusshed.com/pages/item/m2410.html

    Look at the two views to see the solenoids on the front and back.

    As long as bulb exposures aren't too long, a simple button-pusher might be fine. This is, after all, for a Holga. Make it too fancy and I'm sure the camera will refuse to work with it.

  7. #7

    Electronic button pusher?

    The shutter and solenoid from an old press camera might serve as an electrically controled external shutter. These shouldn't be too expensive if the lens is bad or missing.

  8. #8

    Electronic button pusher?

    Wow! Thanks for all the responses. I've been away from the internet for a week (what a weird experience) and this is good info all to return to.

  9. #9
    500+ Posts toniox's Avatar
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    Electronic button pusher?

    My idea to make a simple electrical shutter is to use a solenoid of an old hard drive. I've just tried it with a 1,5 volt size AA baterrie. It move very fast. I've soldered 2 wires to the solenoid as you can see on the picture. We can easyly imagine a sort of adjustable timer in order to make the exposure.

    Attached files

  10. #10
    500+ Posts toniox's Avatar
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    Electronic button pusher?

    Another picture, the moving part is the on the right side of the picture.

    Attached files

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