Sounds a bit like the basis for the bending wineglass trick?
Posted: Dec 1, 2005 9:13am
Velleman produce a "555 timer kit" which can be adapted to produce the start delay that you are looking for. Unfortunately, their kit as sold does the opposite to what you want - it switches on for a predetermined time, then switches off. It can quite easily be altered to do the opposite (which is what you want). If you know someone who dabbles in electronics then feel free to contact me and I'll give them the basic pointers. (Just a case of exchanging the NPN transistor supplied for a PNP and a few mods to the circuit board.) As I remember, the board is about 4" x 4" and powered by a 9v battery, which could probably be used as the power to your turntable also. With regard to switching off after a quarter turn, then probably a microswitch triggered by an arm on the turntable would be the most reliable, (or use an opto switch if you are feeling adventurous!) - Can't remember how much the timer circuit is - probably around $15. Searching the internet should find a supplier. I'm in the UK and I THINK the last ones that I bought were from Maplin.
...the kit referred to has been updated see..