Drawer latches, nitinol, solenoids, etc.

I'm lookin' for a drawer latch that I can drive with a mosfet. What I have is more-or-less like a cash register drawer. I'd like to find something inexpensive -- or at least less expensive than designing my own latch and having to have it sent out to be made. Quantities are low, probably ten or twenty a month.

I'd like to avoid bringing in a 12V line for a solenoid, although (I suppose) a dc-dc converter is possible.

I was hoping to keep the current for the entire product below 100ma, and the electronics only pull a few mA. I was thinking that maybe I could charge up a capacitor or something and then use that stored energy to kick open the solenoid. Off-hand, that doesn't sound practical, but I thought I'd mention it.

I've also been thinking about making (or finding) a nitinol latch. It resolves the issue of the 12V, and the whole mechanism will probably be less expensive than one driven by a solenoid.

Another, possibly inexpensive way to go about this would be to use a small motor and a few plastic gears to drive a pin.

Any suggestions?



Reply to
Mike Turco
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Solenoids do not have to be 12V. It is the amp-turns that matter, so normally, you get the solenoid wound to suit the application.

The most energy efficent, and mechanically simple solution is a latching solenoid. This uses a holding magnet, and needs a bipolar drive.

This is used, but normally in production volumes an A-T matched solenoid is better. If you need to use standard parts, in lower volumes, then a charge pump is a valid solution - keep in mind what happens on a sticky drawer tho.

There are 'linear motor' actuators, that are a low cost motor+nut+threaded rod.


Reply to
Jim Granville

You might try the actuators used for latching/unlatching the doors on cars. Because of the high volume they are quite cheap. The ones we have tried were bought as Nissan spares. Of course being for car use, you need 12V. It use a small motor, hence the current requirements are much lower than for a solenoid.

Regards Anton Erasmus

Reply to
Anton Erasmus

Vague pointer... how about the mechanisms for electronic door locks - not the big electric latches, but the style that just lock / unlock the handle. (e.g., hotels, or standalone battery-operated PIN-pad style)

If it works to unlock (w/ manual unlatch) instead of auto-unlatching, these operate for a very long time on a few batteries.

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