In Reply to: circuit diagram posted by sa.v on 08/06/02 at 10:55 AM:
I haven't got the circuit drafted up yet in schematic form on the computer - just wired together on a breadboard. Really, all that's relevant is when the circuit is powered on, I need something that routes Vcc (+5 VDC) to a particular path for a certain period of time (which is not a precise duration, just a visual effect). Then, after the period of time, the routing changes from Vcc to Ground. I was thinking a one-shot applied to the base of a transistor would do the task, but the pulse needs to be triggered automatically on power-up rather than from a manual trigger.
I've also considered using an RS Latch with one input held high and the other tied to a clock signal. Unfortunately, this method doesn't guarantee both inputs will always be high when the circuit is powered up, so the latch won't always be initialized proper before the first clock cycle changes its state.
Ideally, a monostable multivibrator would work, as it passes Vcc through for the one-shot, but getting the darned thing to trigger automatically is the trick I haven't been able to resolve.