This simple flashing light circuit is powered with 6 volts/0.5A and has a low current consumption when the light bulb is off. The flashing frequency is set by only one capacitor. Transistor T1 may be ...

LEDs are driven with a constant current, with the forward voltage varying from less than 2V to 4.5V, depending on the colour and current. Older designs relied on simple resistors to limit LED drive ...