Drawer latches, nitinol, solenoids, etc.

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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?

Thanks,

Mike




Re: Drawer latches, nitinol, solenoids, etc.
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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.

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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.

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


Re: Drawer latches, nitinol, solenoids, etc.
On Tue, 29 Jun 2004 11:23:25 -0700, "Mike Turco"

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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


Re: Drawer latches, nitinol, solenoids, etc.
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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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