The following needs lots of pictures - I'll add them to the page later.
The is a plan for building a lockbox - a box containing a timer which, once locked,
will not open until the set time is up. This is ideal for securing a bunch of keys to
operate a chastity belt, handcuffs, or whatever you'd like to not be able to remove
for a while :-)
The objective of this design is to be made with easily available parts, and not
require any specific construction or electronic skill.
There are 2 designs:
Internal Lock version - this requires a component that you'd have to buy
from an electronics shop.
External Lock version - this requires no special parts, but is a bit more
fiddly to make.
What you need are the following:
Some sort of large box. I've found the best thing to use is furniture, such
as a drawer of a chest of drawers. In needs to be not too small (around a 6 inch
cube I guess)
For the Internal Lock version, you need to easily be able to stop the box
from opening. Drawers are great as it's easy to stop them sliding.
For the External Lock version, you have to have a lock on the outside.
A cupboard might already have a lock, or a chest or suitcase, or you can
screw a hasp and lock onto an existing box.
A mains cable, with a plug on one end and socket on the other.
A security mains timer. This is a unit which plugs into the mains socket
and you can plug something like a light into it. It has a clock on the front
(either mechanical or electronic, either 24 hour or 7 day) and can switch
the light on or off according to the clock setting. You should be able to
get one of these from any hardware store.
A power adaptor, for converting from mains voltage to something like 3V or
9V DC (usually with a voltage switch), with a range of plugs on the end.
These are usually sold for powering toys or come with rechargable equipment.
Some sort of powered lock device:
For the Internal Lock version, you need to get a low voltage DC solenoid,
which has a rod which pulls across when power is supplied. You can get these
from electronics shops (eg Maplin in UK, possibly Radio Shack in USA).
For the External Lock version, you need a small motor. You can take one
out of just about any small motorised toy, since they almost all use
3V motors, which are about a cubic inch. The best thing to use is a battery
powered hand held fan, which has such a motor inside. In fact, it's better
to use something which already has some gearing and a wheel attached
to the motor - so if you are using a toy car, don't smash it apart yet!
If you've got that lot together, the building is quite easy:
Make a small hole in the back of the box (if you're using furniture,
it may already have a hole, like the gap at the back of the drawer).
If you need to, take the mains socket or plug apart (if you can!)
and poke the cable through the hole, and put it back together so the
plug is on the outside and the socket inside.
Put the mains timer into the socket, and the adaptor into the mains timer.
The next part depends on on what version you're building:
For the Internal Lock version:
Find out what voltage the solenoid uses, then set the adaptor to that
voltage, chop the connector of the adaptor and attach the solenoid wires
to it.
Plug it all in, and set the timer to 'on'. The plunger on the solenoid
should be pulled in, and then pop out when you set the timer to 'off'.
You need to have worked out some method of securing the box using the
solenoid. For instance, if you're using a drawer, drill a small hole through
the side of the drawer (the moving bit) and into the side of the 'shell' of
the chest of drawers. (On the ones I have, the plastic runners which the
drawers sit on already have suitable holes, so I would only need to drill
through the side of the holes.) It will be tricky to work out where to drill
the holes, so measure carefully.
Mount the solenoid (screw/bolt it in place?) so that when the power is
off, the plunger of the solenoid is going through both holes, locking
the drawer shut, and make sure that when the power is on, the plunger
withdraws enough to allow the drawer to be pulled open.
For the External Lock version (pictures further down):
Find out what voltage the motor uses (check the number of batteries if
it's a toy), then set the adaptor to that voltage, chop the connector of
the adaptor and attach the motor's wires (or the springs on the toy's
battery box) to it.
Plug it all in, and set the timer to 'on'. The motor should spin,
and then stop when you set the timer to 'off'.
You must have some mechanism of locking the box from the outside.
This technique involves securing this key.
Cut a small horizontal slot into the front of the box, just big
enough to poke the key through. Put the key in the hole, so that the hole
in the head of the key is just visible inside the box.
You'll need a stiff piece of wire, and attach it to the end of the
motor. If you're lucky, you'll have some sort of wheel already attached
to the motor, so you can attach the wire to that. For instance, if the
motor you have is in a hand held fan, and you've snapped the fan bits
off, you could drill holes in the 'head' (which the fan bits used to
be attached to). If you just have a motor, you could glue something
like a cork onto the spindle with an expoxy glue, or use a piece
of Meccano (Erector Set?). But somehow, you need to have the wire
spin around when the motor is powered.
This is the tricky bit - form this bit of wire into a hook shape
and mount the motor/toy inside the box so that the hook of wire pokes
through the hole in the head of the key (as it's poking through the
hole in the front of the box. The idea is that when the motor is
powered, the wire will spin out of the hole in the head of the key,
which will let you pull the key out (as part of it will be poking
out of the front of the box). You'll have to experiment with getting
the shape of the wire right, so that it smoothly slips out of the hole
in the key without getting stuck. Make sure the motor spins in the
right direction - you may have to swap the wires over to the adaptor
to make it spin the other way.
So, the wire will stop the key being pulled through the hole, and
when the power is applied, the wire will be removed and the key
can be withdrawn.
These pictures show the motor and the wire securing a key.
Imagine the pen is a slot in the box, with the key poking
out of the front, and held in place by the wire. In the
first picture, the key is secured, and in the second,
the motor has been powered, the wire extracted from the
key, and the key can be removed.
You might want to put some sort of 'stop' to prevent the key
accidentally being pushed inside the box.
One 'feature' of this is that you have to put the key into the
mechanism while the box is open, then shut and lock the box. If you're
using a sort of lock for which you need the key to lock the box (like
cupboard keys sometimes are) then you must use two keys, and cut an extra
small slot in the box - put one key into the mechanism, close and lock
the box with the other key, put that key through the new slot so it's
stuck inside the box, until you can free the key secured by the wire.
And to use it:
Put into the box whatever keys you want to secure.
Plug the mains plug outside the box into the mains.
Set the time on the timer to the current time. Set it to be off now,
and to go on at the time you want to open the box (say, a few hours
from now).
Double check the timer setting and everything else - if you
accidentally disconnect something, you might never be able to open
the box again!
For the Internal Lock version:
You'll have to close the box and let the plunger lock it. If you're
using a drawer, with the plunger at the side runner, then you can push the
plunger in with your finger as you close the drawer - the spring will
push it out again and lock the box.
For the External Lock version:
Turn the motor so that the wire is not obstructing the slot for
the key.
Push the key into the slot (not too far).
Turn the motor so the wire goes through the hole in the top of the key.
If closing the box will lock it, then just close the box. If you're using
a padlock to lock the box, close the box and lock it with the padlock.
If you need a key to lock the box, then lock it with a 2nd key and then
push the key through the 2nd hole so it's inside the box.
Now wait.
Once the timer hits the set time, the power will pull the plunger or
spin the motor, and the drawer will be openable or the key freed.
Other thoughts:
You might want to connect a buzzer or a light across the adaptor power
output, to alert you when the box is opened.
If you're using the External Lock version, then when the power goes on,
the key will be freed and can only be re-secured by hand. But if you're using
the Internal Lock version, the solenoid will be open while the power is on
and relock if the power goes off again. Consider setting the timer so it goes
on for 10 mins every 2 hours, then don't look at the timer when you turn the
dial to set the current time. The box will become open at some random time
in the future, but, if you have the Internal Lock version, will re-lock
itself 10 mins later, and re-open 2 hours after. If you didn't add a light
or buzzer, it's just luck if the lock is open when you try the box.
If the timer is mechanical, then switching the mains power off would stop
it 'ticking', and switching it on again would start it again. That means that
if you've set the timer to open in 2 hours, you could switch the power off
after you've locked the box. The box would then only open 2 hours after you've
switched the power back on - in other words, you can only get back the keys
you've put in the box 2 hours after you want them back!
Please let me know if you build this, or if you have any other design suggestions
(although bear in mind it's supposed to be simple to build from available parts).
