AndrewRLynch.com Why yes, that is my real name.

Arduino-powered LED Lightbar

I am still working on this project, but I thought I'd get a start on a page for it.

I have always been fascinated with emergency vehicle lightbars. Since I was a kid, I wanted a toy car with flashing lights on it. Now that I have pursued an education in Computer Engineering (which has its roots in Electrical Engineering), I decided to build one myself.

The supplies I used:

• 32 Amber LEDs rated at 15,000mcd @ 20mA
• 2x 1" diameter PVC pipe (cut to 18" lengths)
• 1x Arduino bare-bones board (from ModernDevice.com)
• 2x TI TLC5916 8-bit constant current sink LED drivers
• Cat 5 cabling (cheap and abundant)
• Hookup wire (abundant)
• 5v 500mA Fused Power Supply (used an old car cigarette lighter charger with end cut off)
• 2x pushbuttons
• A case (salvaged from an old Linksys 802.11b router)
• RadioShack breadboard PCB (looks like a PCB, hole pattern is that of a breadboard)
• Superglue/Hot glue

I began by drawing out how I wanted the bar to be laid out. I measured the back window of my car, and determined that two 18" sections would work the best. I then figured that, although inefficient for car voltage, I wanted to keep everything at 5v, including the LEDs. I could have run more together at 12v, but for my first big project, simplicity helped. I figured I could fit 16 LEDs on each bar, grouped into 8 groups of two. I marked out the PVC to cut 1/4th of the circle out, creating an opening for light. I also marked out where the LEDs would go on the back.

I cut out the channel in the PVC using a Dremel-like tool. This proved to be the easiest with such a small diameter. I also drilled out the holes for the LEDs and countersunk them with a rotary tool bit. I inserted each LED into the hole and used a spot of glue to hold it in place. Superglue is what I had lying around, but hot glue might have worked better. The wiring came next.

I grouped two LEDs together to create 8 channels per side. I did this because the LEDs were rated at 2.1V each, and together they drop 4.2V, plus the constant current feature of the TLC5916 made 5v ideal. I then wired some CAT5 to each of the negative terminals of the LED pairs, and ran all the positive terminals to +5v. Each of the 8 negative terminals would go to a pin on the TLC5916. The two TLC5916 (one for each side) chips are housed on the RadioShack breadboard PCB. I cut off the unused portion.

The Arduino sends shift-register like signals to the TLC5916s which are in series. The Arduino shifts out 16 bits, and then latches the drivers to display that "frame" of animation. It also listens for button presses to change the flash mode of the whole bar.

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