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

Henner Zeller h.zeller at acm.org
Mon Jul 15 03:57:56 UTC 2013

```On 14 July 2013 20:53, Martin Bogomolni <martinbogo at gmail.com> wrote:
> Quick thing--
>
> Remember that Fire Code requires that any electric door strike, or
> magnetic strike, must allow someone to leave without being impeded in
> a panic.  On magnetic doors, this requires a panic push bar that
> physically breaks the electrical connection.   On mechanical electric
> strikes, this requires that either a pushbar or simple lever be
> pushed/rotated to bypass the electrical lock.

The regular lock will just work the way it is now - by rotating the lever.

-h

>
> -M
>
> On Sun, Jul 14, 2013 at 10:41 PM, Jake <jake at spaz.org> wrote:
>>> 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.
>>
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```