Arduino Knight Rider with 8 Blue 12v LED Modules

This project is intended to make a bunch of small leds in a row flash back and forth to look like the car on knight rider

• In this case the hardware is 8 mini blue LED modules $2.50ea http://www.usledsupply.com/shop/smd-blue-3528-mini-led-modules.html running at 12v DC so a Darlington Transistor Array (ULN2803A) is needed and connected to the 8 output pins on the arduino it is also fed (-) 12v to the GND pin and all the leds are fed (+) 12v so only the (-) is switched with the (ULN2803A) the (ULN2803A) is rated at 500mA/Ch and there are 8Ch but we are only driving 2 20mA leds per channel and a resistor so there is plenty of power left if you wanted to add more LEDs

• I also used a pot on analog input (0) so you can change the speed of the effect on the fly without having to reprogram it (it is also mapped to an adjustable range for better control)

For a video of it in action http://www.youtube.com/watch?v=stk3C2Zs2cc

View The Code for the Arduino

you could also use this same circuit (just replace the leds with your 12v devices) to control/power 12v relays or small motors and other devices using your Arduino or you can use RGB LED Modules or short sections of strip instead of the single color modules but with only 8 channels you will only be able to control 2 RGB Circuits and you will have 2 unused channels

if you are looking to control longer sections of RGB Strips you may want to check out Control up to 64' of RGB Flex Strip