Thank you for your replies,

> A circuit I use to power solenoid clock mechanisms has just a
> capacitor to operate the solenoids, which are pretty hefty. I've
> not measured the coil current but the DC resistance is 3 ohms

The Solenoid I have measures 7.8 Ohms when I use a DMM.

> Using the capacitor means the
> power supply can be much smaller than if it had to supply the
> current directly. It does droop a little when fast-stepping but
> not enough to affect the PIC.

I mentioned this as one of the things I had considered (the caps). I
did what I thought were the correct calculations, but now I'm not so
sure. I didn't count the solenoid as an inductor, and simply pretended
it was an RC circuit, calculated T, multiplied it by 5 and said that's
how long it could supply the current. I suppose having the L in there
would change things. Wouldn't the activation period need to be about
1/4 (maybe a bit more) the period of the LC oscillation?

Jake
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist