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I would like to get my hands on a mechanically-set timer (wind up is fine, so that it's self-powered) which sends a small electrical pulse to a mag-lock once the timer goes off, thus causing the mag-lock to open. Is there anything out there that does this?

If not, what would be the cheapest / easiest way to replicate such function, i.e. some mechanical way to produce a small electrical impulse once a mechanical timer finishes. I don't mind electronic methods, but since this is for heavy outdoor use I'd prefer a purely mechanical setup.

Engineer
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In principal it should not be very difficult to adapt an off the shelf mechanism like a mechanical alarm clock or kitchen timer. They will already have some sort of latching mechanism to activate the bell after the elapsed time so it should be a simple matter to adapt this to close an electrical contact.

Having said that I'm not entirely convinced that a mechanical system is necessarily going to be any more rugged or reliable than an electronic one. As already mentioned in other answers a mag-lock will need a reliable power supply and a timer circuit is simple to achieve with either digital or analogue electronics and can be potted of placed in an IP rated enclosure to make it pretty much indestructible compared to any kind of clockwork system.

Chris Johns
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A mag lock typically uses 12 volts at low current to power the electromagnet to remain locked. The unlocking mechanism trips the power to the electromagnet. Mechanical delay relays do exist, but you would need one that has a normally closed relay that would be opened by the mechanical delay.

morristtu
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