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"Flashy" Pinewood Derby Cars PDF Print E-mail
Written by Aron Hoekstra   
Saturday, 09 April 2011 09:30
My sons have been in Cub Scouts now for 4 years, up to now I think I've made some pretty cool cars.. Bumblebee & Barricade from Transformers, Mario Kart, and a Halo Warthog. But nothing has really had that 'WOW' factor I was going for.. So this year, I decided to light things up a bit by embedding some electronics in their cars. I searched the rules and found nothing prohibitting electronics, so long as it doesn't aid in propulsion. We had just seen the new Tron Legacy movie, which my younger son, Adam liked so for him we agreed to make the Light Runner car, as seen in the movie. My older son was a little harder to think of an idea.. I would have to make it have lights some way too and came across pictures on the internet of someone else who had done a Wiimote and thought I could do it a little better with some real working lights.

Here are the results..

More Detailed Build Process............

Tron Legacy Light Runner
The Light Runner was a pretty time-consuming build, as I did a bit on planning. The hardest part was hollowing out the inside of the car in a way that'd allow me to thread the EL wire through the car. I ordered 10 feet of Thin Aqua wire from Glowire along with their EL Driver that works on a single AAA battery. I know that driver says it does up to 3', but I pushed it to 5' and it worked fine. Working with the EL wire can be a task in itself. It took me an hour or so just to get the wire soldered onto the driver correctly. Once it was on there, I shrunk some heat shrink tubing around the connections to ensure they never come lose. Since it's one solid, continuous strand of wire it was necessary to go in & out of the car so it would only light up in the desired spots. I considered just scoring the wood and taping/painting over where I didn't want it to show but didn't think that'd provide the right look. This method of having the holes allowed the wire to stay taught, and it did use some scoring in the wood to keep it where I wanted it. We had one little mishap with the paint. In the pictures below you'll see when we first painted the car it has a shiny wet black finish. It looked great, then I threaded the wire through and put a few coats of clear coat over the entire thing. I wanted to do this to protect the paint and the wire, however it had a side-effect of dulling the paint and taking away that pretty shine. I don't know how this happened, or why - I'd have thought clear coat should make it shinier, not less.. Oh well so here are some pictures througout the build process.

Wii Remote
The Wiimote was a pretty fun build. Since I find the block cutting to be the most time consuming part, this one was quite easy. My son was able to do most of the filing/cutting himself. I hollowed out the bottom with a rotary tool (wow do those come in handy!). I've seen other Wii Remote cars where the buttons were just drawn on and thought it'd look much better if they were raised like real buttons. So I found some thin circular wood peices at the hobby store. However, they weren't the right size and they were far from being actual circles. So after toying with trying to sand them down by hand, I got the idea to use my rotary tool again. I was able to drill a small hole in the center of the circle, then mount the piece of wood onto the rotary tool, and spin it up against a peice of sandpaper. I was able to slowly get the button to the right shape, and by tilting the rotation right at the end, give it a nice rounded edge. Then I filled the small hole in the center with some wood putty & sanded. The hardest part was cutting the directional pad out of a piece of the same wood. That had to be done by hand was a giant pain in the butt! Finally we were able to glue the buttons into place and paint.

As for the electronics, I built a PCB using one of those Radio Shack PC boards, I also picked up the smalled higher voltage battery I could find there, a small 12V "27A" battery apparently intended for remote controls. Strange, but it'd serve the purpose. I used a 5V regulator step down the voltage into the processor. For the brains I used a relatively cheap but versatile PIC 16F628 microcontroller, ordered from Sparkfun. I have a PIC programmer that I've used for numerous other projects. I wrote the code in C, using the Hi-Tech PICC Lite compiler. The code is very straight-forward, and can be downloaded here. The coding is atrocious and is not optimized, but I didn't need it to do anything other than flash the LEDs. It does the Wii remote "startup/connecting" flash routine, then goes into a chase sequence. Finally, I used a resistor pack and 4 blue LEDs. The battery holder I kind of rigged together stripping the parts out of some old enclosure I had laying around. Soldered it all together, mounted the LED's into place and there we have it..

A couple of videos to show off the lights..

Overall, we had a great time building these cars. Now the question is, how do we top these next year?

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