Finally I arrived at a silver-foil-and-wire method. Basically, one of the wires coming out of the LED is cut, both ends are stripped and fed out of the underside of the tray and when the box is slid open the two wires come into contact with some aluminum foil, closing the circuit and lighting the LED.
It's only coin cell powered, so it won't last for too long, but it properly works and everything.
I filled the tray with a clear epoxy but added a little colloidal silica to the mix to give it just a little diffusion. The effect is great, but with hindsight, I should have sealed the inside of the box tray, so that the epoxy didn't stain to outside of the box. It's only a small thing, but it kind of gives away that the box has been hacked before you open it.
It's portable, a gadget, home-made and unexpected. What's not to like?
There were two prototypes undertaken.
The first was an arrangement where I filled the box with long thin sticks. I coated the sticks with a combustable paste which then dried. The idea was that when you rubbed the sticks against a roughened surface, they caught fire. The Missus pointed out that this was what people called "having a dog and barking yourself". So I binned that one.
The second was where I put a one watt LED in the box with a PICAXE chip and a photoresistor. Here, when the box was opened, the PICAXE sensed there was an increased level of light and tuned on the LED. This time the Missus pointed out that you would want the light when it was dark and to cut a long story short, I binned that one too.
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