MortiSafe timer controlled key safe

Also see my other design which uses specific components which you can order over the web in UK, whereas this one uses generic parts.

It's a mains cable, with a mains timer plugged into it, and an transformer (such as is used for toys and rechargeable devices) plugged into that.

This goes inside  a box (this is a metal cash box), which has a solenoid (the black thing in the pic) positioned (fixed here on some blocks of wood) so that it gets in the way of the locking mechanism. The solenoid is powered by the transformer plugged into the timer.

In the picture below, you can see the lock is half-way closed. The power is off to the solenoid, so the rubber band (crude but effective) is pushing the solenoid's plunger into the lock. When the key is turned so that the lock hook is pointing upwards (locking the box), the plunger will snap into place, preventing the lock hook from turning, and so locking the box.

Set the timer before locking the box - for instance, set it to power up in one hour. Once the box is locked, wait. In an hour, the power will energise the solenoid, pulling it out of the way of the lock, and you can open the box.

There are still some issues I need to sort out:

• I think a capacitor may be needed across the solenoid to absorb the initial current surge, though not sure what value
• I need to find something a bit better than an elastic band, such as some springy metal, since the solenoid plunger is only pushed in one direction by the power being applied 
• Need a suitable means to mount the solenoid in place
• Not sure if the box should be electrically earthed, and if so, not sure how to do it (I don't want to run a wire out of a mains plug)
• Need to cut a hole in the box to run the cable out

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