Abstract:

Find out the common cathode and the common anode: firstly, we find out one power supply (from 3V to 5V) and one resistance of 1KΩ (or several hundreds of ohms); the VCC will be connected to the any two feet of the GND after being connected with the resistance in series; there are many combinations, but there shall be one LED which can give off light and one being found out is enough; then keep the GND still and let the VCC (being connected with the resistance in series ) touch the feet left one by one; if there are multi-LED(generally 8)，it will be the one of common cathode. On the contrary, keep the VCC still and let the GND touch the he feet left one by one; if there are multi-LED(generally 8), it will be the one of common anode. The digital multimeter cab also be used; the red test pen is the anode of the power supply and the black one is cathode of the power supply.