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I found these instructions to convert an RC car to a robot on instructables a while ago and now I have a use for it. An RC car doesn't make a perfect robotic car, but it's cheap, fast, and would be a great way to start. I have an old RC car that I got for $5 from the thrift store that I'm starting this with. This is meant to be my starter car, and I hope to work out something better later. The two main shortcomings I've seen so far are turning and speed control. The car uses a servo like thing to turn the front wheels and as far as I can tell your choices are turn it all the way or not at all. I could be wrong, and I'll have to try sending a PWM signal to it, but even if that won't work this problem can be fixed by replacing the on-board servo with a regular hobby servo hooked straight to the micro-controller while still using the cars main board for forward and reverse. As for speed control, I can't think of any way to do it. I would really like to put an encoder on somewhere to get good movement precision for SLAM purposes, but most RC cars that I've seen don't really have a good place for an encoder. If you have any suggestions for improvement after reading the article I'd love to hear them. Hopefully someone finds this to be useful. |
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Hi, @Stevo! I also did that. I also achieved to receive the radio emitter signal in the onboard Arduino (besides controlling the engines), which allows me to send some commands to the arduino remotely (I think I will have to put a netbook or something on top of it for sensing, so I will have a wifi to connect to the arduino, but receiving from the radio emitter feels good, hehe) Maybe you want to read through this thread. |
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One thing I've found with RC car speed control is that the motor controllers are very non-linear. From a control perspective they look like servos, so you expect to have full 0 - 180 control range (with 0 being full backwards, 90 stop, and 180 full forward) but often I see 90 being stop and 95 being full speed. I've taken to replacing them with H-bridge controllers (bought or built) and driving them with the PWM output from an Arduino. Having the full range of control (now a full 0-255 in either direction) allows better, more granular, setting of the speed. We too (I do this with some high school students) struggle with how to get wheel encoding done. Right now we're looking at putting a slotted disk over the wheel (like a hubcap) and seeing if we can just measure the ambient light changes as the wheel rotates. We're also thinking about trying to use an optical mouse under the car to measure distance traveled - no idea how that might work out. Good luck with your project. Have fun. |
