In article .uk,
Ed Sirett wrote:
Low power 555's handle minutes without problems, but this application
probably only really needs around 10 seconds, and it doesn't need to
be accurate.

Wouldn't a slow release relay/contactor be suitable?

You can buy variable delay relays from RS etc, but they're far more
expensive than making your own.

--
*I have a degree in liberal arts -- do you want fries with that

Dave Plowman London SW 12
RIP Acorn