A friend asked me this because I am a EE student. But since I am pretty much, eh, below-average, I don't really know what to do except use a capacitor or something. Anyone? It should blink once when powered, then stay off til it gets switched off and then on again.

 

 

Power supply? LED spec? Blink duration?

 

1 second blink, LED 1.3-1.6 v, power supply is 5v

all of the above is a quote

 

You can use 555 Timer in Monostable Mode, in this mode it is also called one shot pulse generator. The 555 timer will generate a single pulse that will turn led ON one time and that is it because the chip reset is never engaged (it is tied to the power supply) so the chip is never reset. The only way to reset the chip is to turn off the power. The use of 555 timer also allows you to control how long the led stays on. So using this chip will allow you to accomplish both of your goals, turn led on one time, set how long led stays on.

555 Timer wiki: http://en.wikipedia.org/wiki/555_timer_IC

 

If the time interval is not critical you could use a simple circuit consisting of a transistor, a capacitor, a diode, and a few resistors.
Below is the simulation of such a circuit.
You can change the value of R2 to vary the LED ON time.