Simplest LED Flasher Circuit
Need to flash an LED on and off but do not want to make an entire 555 circuit?
Why not try this simple circuit
It consists of two resistors, a capacitor and one NPN transistor that’s it nothing else other than the power supply and LED
I tweaked the values to get a nice flash out of it.
In my implementation I have a 4.3k resistor connected in series with the emitter on a NPN transistor then the collector has been connected to a LED with a current limiting resistor on the LED to ground
In parallel with the transistor and LED resistor there is a 330uF capacitor
In this circuit a 1k resistor charges the 330uf capacitor until the voltage became large enough for the emitter-base junction to avalanche this discharges the voltage in the capacitor through the LED and current limiting 100 ohm resistor.
Follow this link to Dick Cappels, the creator of this modern wonder.
PDF datasheet for the 2N3904 NPN transistor but almost any general purpose NPN will do.