Jan 302011

This project requires you to be somewhat comfortable with the breadboard and placing components in the proper sequence.

In particular, pay attention to:

  • The negative stripe on the capacitors (should always point to ground)
  • The pins of the transistors (its helpful to know which are E,B, and C)

To build this circuit:

  • 9V battery or power source
  • Transistors (two NPN, we used 2n3904)
  • Capacitors (we used 100uF)
  • LEDs (2)
  • resistors (2 of 10k Ohms)
  • resistors (2 of 470 Ohms)
  • push button switch
  • jumper wires

Alternative breadboard layout for LED flasher:

If you want a simpler layout with less jumper wires, here’s another version we built. It’s the same circuit, but the transistors and capacitors mirror each other so be mindful of polarity!

alternate layout

Video of dual LED flasher in action:

where I test the circuit in Ktechlab before showing the build test