One year, actually many years ago, I got a micro-rc car in my stocking. These tiny cars (1 / 52 nd scale i think) are powered by an onboard capacitor that charges from the handheld controller itself. A couple examples (pre-hacking) of these cars are below.
Typical Micro Scale RC Car Used in this project
Getting Down and Nerdy
After chasing around the cat, I wanted more. I had been playing around with Linux and decided it might be cool to control it from the computer. I didn’t have any kind of fancy I/O board on my PC, but I did have an old school printer (LPT) port. These big throwbacks from an older age are fairly robust, and in linux, fairly easy to control the voltage level to 0 or 5 volts.
The basic method is to over-ride the mechanical switches on the controller. When the switches are pressed, they have a low resistance across the terminals (near zero). In this project a transistor is inserted between the terminals of the switch, and the transistor’s resistance is set low by setting the LPT pin to 5 volts.
The lpt port pins (6,7,8,9) are used to control Forward, Reverse, Left and Right in the controller. In addition to this program, I had to build a simple circuit to bypass the buttons on the remote control. This is because even in the low state, the Control and Ground pins still form a complete circuit.
The selection of resistors / transistor was done ad-hock. Feel free to experiment until you get it to work!
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- Another Example of the Original
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- Typical Micro Scale RC Car Used in this project
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- Inside the project box
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- After packaging the RC Car project
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- Circuit Diagram
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- C Code - Linux Only
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Code
History & Internet Fame
So, I posted the project on my personal website I had through my university at the time. Nothing much happend, but then I started gettting TONS of emails.
It turns out it was picked up by Hackaday.com ; I hadn’t heard of the site (although its AWESOME), and definitely didn’t submit it to them…
So ever since the article, I’ve gotten at least a few emails a year about it, mostly from students overseas.
And then… it happped again. I got a few more emails than usual, and it was because it no longer worked with more modern versions of linux, and someone posed the question on www.linuxquestions.org. Over the period of a few days, a bunch of people helped fix the problem.
I thought it was a cool example of the nature of the internet.