Thanks MP, that's really interesting! I like this idea and I'm looking at the datasheet. What would be the easiest way of feeding it a slow voltage increasing from 0v to 5v or 9v? Can it be done with a simple capacitor charging circuit? If so, I'll have a look for some information and try to build one. Ideally I'd like the circuit to work with as little battery power as possible and this seems like a good solution. Thanks again!