Background

Vampires are the usual sort. They sleep in coffins during the day and awake when it gets dark. Apart from the normal ways of killing them, they are immortal and so, despite their thirst for blood, they will never starve to death.

Currently there is a plague of vampires and although they could be killed by the usual means, it is decided to try and make use of them.

The setup

A vampires lies in its coffin. When light ceases to leak in under the lid, the vampire awakes. It lifts the lid and sits up. However the lifting of the lid operates a switch that, after a short delay, turns on a bright lamp. Seeing the lamp, the vampire quickly retreats back into the coffin. This causes the light to go out. The sequence repeats indefinitely. A crank mechanism attached to the lid operates some machinery and so the vampire's ceaseless movement is converted into useful work.

Problems

In the olden days there was no electricity, so switching on a lamp on with a delay might be difficult to implement. Also, lamps bright enough to simulate daylight would be very hard to make.

Assumptions

There are plenty of vampires to experiment with and banks of coffins would be possible.

Vampires can survive under moonlight and when subjected to a dozen or so candles. Above this level, the brighter it is, the faster they move to avoid it.

Please ask for clarifications before answering.

Question

What is the most efficient way to utilise vampire power? How should I design the setup? Rough diagrams depicting the machinery will be welcomed.