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I'd like to drive a pair of mechanical shutter / apertures with an electromagnet. For those curious, we're using a shutter from Edmond optical. For the particular application, I'd like to design a compact actuator to drive it. (I had considered just hacking a camera lens with a shutter, but couldn't find one that was large enough for my needs).

So at present I am thinking about attaching a neodymium magnet to the lever of the shutter and then using a series of electromagnets to push it between open and closed. Which all leads to my first question: how can build compact electromagnet?

It seems like the steps involved are to find a solenoid and then to drive it with a decent voltage difference. I wonder if anyone could recommend a good small solenoid for such purposes. Does it make more sense to roll my own with an iron core and insulated wire?

My second question is more open-ended: can you think of a better way to drive such a shutter? How would you design the shutter motor?

UPDATE: in response to comments:

@tyblu the shutter needs to be open or closed in about 500 microseconds (but exactness is not important).

@bt2 a solenoid is interesting, are you thinking of hitting the lever and letting momentum carry it across to the close position?

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  • \$\begingroup\$ You can buy solenoid motors, is that what you are talking about here? I would think it much easier to buy a solenoid motor than create your own. You can search by stroke and power. I'm guessing you don't need much of either. \$\endgroup\$ – bt2 Jan 19 '11 at 5:32
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    \$\begingroup\$ How quickly does it have to open and close? \$\endgroup\$ – tyblu Jan 19 '11 at 5:34
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    \$\begingroup\$ Shutter != Aperture. A shutter has two states - Open and Closed, and cycles between the two very fast. An aperture, (which is what you linked), often will never fully close, and has degrees of openness, related to the size of the opening. If you want to control a shutter, an single electromagnet will suffice. If you want to control an aperture, more is involved. \$\endgroup\$ – Connor Wolf Jan 19 '11 at 6:10
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You could use a servo with a linkage arm to close the shutter. I'm looking at doing this right now, except I need to precisely control the aperture. A servo will give you (relatively) precise position control, and it's fairly easy to interface with.

If you need to close the shutter very rapidly, then your best bet might be a solenoid. I wouldn't, however, recommend building your own. There's plenty out there that'll do the trick and probably work better than you can design - it'll also save you time. You'll need to use a spring to restore the shutter to the open position. You might try searching Digikey.com to find some.

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As was already stated if you want to be able to control how open it is then you will need some kind of linear actuator and a mechanical linkage to the lever that opens and closes the aperture. If you are just alternating between totally open and totally closed then an electro-magnet may work. A Google search for linear actuators may provide you with what you are looking for.

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You need to rethink your requirements. Opening and closing a mechanical shutter in 500 microseconds is an extreme demand. Most mechanical shutters take several times as long to open completely. The shutters in SLRs achieve sub-millisecond exposures by opening partially and moving the opening across the frame so each portion "sees" light for a brief interval, but the overall exposure takes longer. Extremely fast opening and closing times are the domain of electro-optical shutters.

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