There seems to be a popular trend right now at multiple retail stores for marquee lights. I have seen them at Target, Jo-Ann Fabrics, and a few other stores. Sadly, most of these seem to all be static on or off lights without any fun patters, what a waste is that! I picked up a few letters from Target and now I'm hacking them to be controlled by an Arduino Mega clone. Follow along to learn how.
Step 1: Prep Your Letter
The Target letters are easy to access the LEDs inside. Start by removing the screws in the back cover and then you can pop it open. Inside you will find a small circuit board, and a button attached to the lid. Clip the wires near the board going from the circuit board to LEDs near the circuit board, we wont need the board for this project. Clip the wires from going from the battery compartment to the switch/pcb near the battery compartment. Now the PCB and switch are free to be removed, go ahead and pull them out and toss them or save them for another project.
In my letters there are two white wires running to each LED, one of the wires has a black stripe though. This is the ground wire, do not clip any of these. Starting at the LED that the pcb was connected directly to, clip the solid white wire (again, not the one with the black strip) as it exits the first LED and heads to the next. Move to the next LED and clip the white wire that leads to the LED following. Continue until all LEDs are no longer connected by the solid white wires but are still connected by the black stripped wires.
Step 2: Measure and Cut Your Ribbon Cable
I used ribbon cable to run all the wires because it keeps your wiring cleaner. Place the ends of your ribbon cable near the last LED in the series and then wind your cable through the rest of your letter back to the first led in the series. I would then recommend leaving about a foot of wire (or more depending on how you want to place your final letters) to stick out of your letter that you can use to place your electronics conveniently. Cut the wire. You will need as many wires as you have LEDs (in the case of this S, 12) plus one wire for ground.
Step 3: Solder Resistors
Since we are no longer running the LEDs on a shared 3V power supply, we will need to ad a resistor for each so they do not burn out. Trim one side of each resistors leads to about 3mm in length and then solder each one to the short end of a row of male header pins. Make sure you don't bridge the pins with solder.
Step 4: Solder the Cable
Clip the other ends of the resistors two about 3mm again and solder on your ribbon cable. Spare one wire for your ground wire and solder it to a single header pin without a resistor. Now starting with the last LED in your letter, solder one wire from the ribbon cable to each LED and the spared wire (I used the single wire with the red stripe on my ribbon cable collection) to the ground wire of your letters.
Step 5: Program Your Arduino
Plug the headers of your ribbon cable into your arduino with the ground pin going to one of your ground sockets. Now program your Arduino to blink the patterns you would like to see. I started with the basic Blink sketch from the examples and made a very basic (and I know messy) example. This is just meant to be an example of how to get started.
Step 6: Cover and Enjoy
Place the cover back on your letter, I was able to thread the ribbon cable out the hole where the button used to got but I might ad a hole in the back to hide the wires. Plug everything in and try your code. Now you can enjoy a nice animated sign instead of a boring static one.