Bring in some muscle to your output pins with 8 mighty Darlingtons! This driver chip contains 8 drivers that can sink 500mA from a selectable 5V or DC input voltage supply and has kickback diodes included inside for driving coils. This will let your little microcontroller or microcomputer power solenoids, DC motors (in one direction) and unipolar stepper motors. The GPIO Pins are connected to ULN2803 inputs through a DIP switch, with the its outputs going to two array of Wire-to-Board header. Alternatively, these ports can be used to supply +5V or input voltage to other external circuitry, or embedded devices.

Please note that this is an ‘open collector’ driver – it can only be used to connect the load to ground and there will be a 1 Volt (or more) ‘drop’ across the internal transistors.

Schematic diagram            Raspberry Pi GPIO Pin numbering             ULN2803 Datasheet

Optional driver to install – WiringPi

1. Install GIT
sudo apt-get install git-core

2. Download WiringPi
git clone git://git.drogon.net/wiringPi

3. Enter the directory of wiringPi
cd wiringPi

4. Install wiringPi
./build

5. Test GPIO port
gpio mode x out (x = 0~7)
gpio write x 1 (x=0~7, 1=On)
gpio write x 0 (x=0~7, 0=off)