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

Jake jake at spaz.org
Mon Jul 15 03:41:23 UTC 2013

```> The motor Scotty found takes about 300mA at 6V when free-running (so
> 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.

there are at least ten 1000 microfarad capacitors rated at 50 volts in the
pile, and i can certainly find more.  But i think the math is more
complicated.  But since it's based on voltage squared, one 50 volt
1000 uF capacitor is the same energy as a 20,000 uF capacitor rated at
11.1 volts.

anyway that motor sounds hella weak.  The motor i already mounted on the
door is rated 24 volts and probably can take a good amp or two at least,
which is a lot more power.
```