[Rack] Electric door strike working again. Use your Pin or key to get in.

Henner Zeller h.zeller at acm.org
Mon Jul 15 03:30:40 UTC 2013


On 14 July 2013 20:04, Jake <jake at spaz.org> wrote:
>
> I still think the motor I installed might work if we give it 30 or 36 volts.  It is rated at 24 volts but it's a high-quality motor.  We should try it.  It might take a few amps of current though.
> So if we're going to move away from the apartment original 24VAC 1A (or whatever it is) we might as well find out if the motor I installed can actually handle it.
> There is a geared motor from the ATM pile, which is meant for the cash slot closer.  I believe I can find enough capacitors to allow it to reverse (it's going with the spring in the reverse, so it should be easy) and I can make it work.. so that's one solution.

The motor Scotty found takes about 300mA at 6V when free-running (so
for no-load 'return', maybe 500mA with load). It runs about 1 second
for the amount of time we need. That is about 1.8 Joules.
Say we can charge up a capacitor to 18 V (peak voltage of a bit more
than 12 V AC) and drain it down to 4 V (when this particular motor
just works), then we'd need about 20'000 microfarad ( 2 * 1.8 joules /
 ((18 - 4) volt)^2 ). The calculation would be similar for other
motors found in the pile.

That should be doable.

>  And then we don't need to come up with a new wiring arrangement for the thing.

Sounds good.

> remember the sewing professionals on the 2nd floor probably have a button of their own with which they buzz people in.  So it's nice to stick with the original wiring for that reason.

Yeah, didn't know if they actually have a buzzer. But the less we need
to modify, the better.

-henner


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