Auduino and a scoreboard

Hi guys this will be my first project (maybe) I have a scoreboard for a shuffleboard table I made, Red and Green score goes to 21 points for each one. Right now I have two old rotary dials off of phones one red one green. when you turn the dial say to 4 it pulses and turns a mechanical relay so a red light behind the No 4 lights. I would like to do this with the arduino. Just don't know how to get started (sketch) When I dial a 4 I would need the sketch to somehow turn on the 4th pin in a series of 21 (for the green team then I could copy same thing for red changing the pins of course) then would have to go up 6 more pins in the series when say I dialed a 6 Any suggestions Thanks

Well, a rotary dial is just a switch, so it behaves just like any other switch. All you need to do is to count the pulses. See Nick Gammon's tutorial on switches at

You'll need to debounce them.

Sounds like a cool project!

How are the lights powered? What voltage & current?

Right now there Christmas tree lights but I will change to powering 2 or 3 LED's for each Arduino Pin I think that would be ok only two groups (group would be 2 or 3) of lights will be on at any one time

Keep in mind that an Arduino pin is only guaranteed to output 4.2V at 20mA, at higher current the output voltage droops. You can typically put two Red LEDs in series with one current limit resistor on one pin. Any other color will usually have a higher Vf (turn on voltage) and you would need to wire them in parallel with a current limit resistor each.

thanks the green LED's I have are 3.4 volts at 20ma so Im assuming that I can only drive one led on one pin The red LED's are 2.1 volts at 20ma so the voltage is only half of the total per pin does that mean I can drive 2 LED's on one pin Rick

Two reds in series yes. Two greens in parallel, but at lower current. Fortunately super bright LEDs these days are Really bright: Some examples: