The Low Rider - Blue LEDs for a neon look undercarriage.
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Start by ordering 2 LED bars from Sparkfun Electronics, SKU #COM-00678 for the blue one. They also carry green, white and tri-color models. Each unit comes with a pair of mounting brackets and a cable. The mounting brackets are of no use in this project but you can maybe use for something else. Put them in your junk box. |
| You'll be using the robot's AUX port to power the LEDs, and one cable isn't long enough. So i cut off the connector on one end of each of the cables and spliced them. I added a 200 ohm resistor in line to give additional current limiting protection. Alertatively, you can just splice the connectors as the photo on far right shows. This isn't as robust though and would be prone to coming loose. |
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On one board pry up the header and then snip off the plastic part, leaving the two leads sticking up about 1/4" (4-5 mm). You'll be connecting your power cable to this. I did this because the part of the board you see here will be facing the top of the robot. Space is very tight and there isn't room for the header and the cable plug. The cable plug will seat into these leads nicely. Remove the other header that isn't pried up completely by desoldering it. You'll be using the holes where the that connector is to bridge power to the other board. |
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In the place where the 2nd header was, solder a pair of wires, preferably red and black. Red goes in the "+" hole. The holes are labeled + and -. Very convenient. Notice the trimmed leads sticking up on the first header on the right of this photo. |
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The red/black cables go to supply power to the other board. Put the boards on the bottom of your bot to get the best measurement. I found wires about 2 1/4" to work well (about 55 mm). As this photo shows, + goes to +, and - to -. So this is a parallel circuit. |
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I mounted the boards permanently using wood screws through the circuit board into the plastic at bottom, but you could use double sided tape if you want to be done quickly. Tape will work but it won't be as robust and will come off eventually.
If you want to mount permanently, use a small drill bit (1/8" or so) to drill into the plastic and then drill a hole in the circuit boards. CAREFULLY. watch where you are drilling on the circuit board. If you drill through a trace on either side you could kill the lights. Look on both sides of the board to be sure before drilling. |
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This photo shows the small wood screw I used to attach the boards. You can see the hole in the circuit board that i have drilled. Make it big enough for the screw to fit through easily. Notice how close that hole is to one of the +/- power terminals. I add electrical tape to prevent shorting those two with the metal screw. It doesn't short but I still put it there for safety. I also tape the entire bottom surface since there are several metal contacts exposed there.
One of the boards is already screwed into place you can see. |
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Here you can see both boards in place. The small piece of tape to insulate the leads from the metal screw. |
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The robot's AUX port just above the LED panel provides power. The power pins are the two far right pins. Plug it in and try it. If no light, unplug and flip over your connector. If you plug it wrong, the LEDs just won't come on. There shouldn't be any smoke effects.
The two spliced cables fit very nicely on the back of the bot, threading down through the battery compartment. The battery will sit on top of this cable. I have added electrical tape around the resistor that is spliced in series on one of the cables. |
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A close up shot of the cable where it plugs into the board with the protruding leads. Notice that the cable connector is lying right up against the battery compartment wall. There is no room for the header that was on the board. This is why i trimmed it off. You coud as well just solder wires right into the board, but this gives me the ability to remove and replace the boards. Like if I wanted green LEDs one day, blue another. |
| ...And voila, the finished product |
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