When a couple of colleagues got Arduinos, I finally got round to getting hold of a starter kit off ebay. It's a very simple kit, with a breadboard and a selection of components that include resistors, capacitors, LEDs and transistors. It also had a couple of circuits pinched off the web to get you started, and they seemed as good a place as any to get started.

With the first one, two LEDs blink on/off alternately. The circuit comprises the following components:

• LED x 2
• Transistor x 2
• 10µF Capacitor x 2
• 470Ω Resistor x 2
• 10kΩ Resistor x 2
• Standard 9v Battery

These components are laid out as in the following circuit diagram:

What's Going On?

The alternating effect must be produced by the transistors being switched on / off by the capacitors discharging and charging. Each transistor can switch the LED on or off, converting the smooth exponentially discharging output from its capacitor into high or low once a threshold is reached.