RC car

Let's Make Robots
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H-bridge.png (33233Bytes)

Ok, so I'm working on a plan to bring my little brother's little Niko RC car (you know, these models that suddenly break down for no reason at all after three charges) back to life. The plan is:

  1. Yank out old electronics (fun job, done ^^)
  2. Test steering servo and current draw of drive motor
  3. Build new electronics

Step 2 will be done by tonight but I have a few hickups on step three.

Basically, I'm going to refit the remote with two mini-joysticks and an xbee module. Now here's the thing: I've read that the xbee has onboard ADC's and I absolutely love this (no need for a microcontroller in the remote) but I can't seem to find a lot of info on how this whole system transmits it's data. With "transmitting it's data" I mean: what comes out at the receiving end and how can I read the ADC's output with my ARDUINO in the car (first time I'll be using arduino :D). Is there anyone here with any experience in this department?

Also, I've built a design for a simple H-bridge and wanted to know if it looks any good. So if you could comment on that, that would be great!

Thanks a lot guys (and girls)!

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I can’t help with the xbees,

I can’t help with the xbees, but here are some thoughts on the h-bridges and electronics.

Your schematic doesn’t show current limiting resistors on the base inputs to the transistors. These are recommended to protect you processor’s outputs in case the circuit tries to draw too much current. What transistors are you using? Will they be able to handle the current of your motors? Same goes for your diodes; make sure they are rate high enough to handle your max motor current. Bigger (more current handling) components won’t hurt, but they can save you.

You can measure the stall current of your motors by preventing them from turning while measuring the current at full voltage.

One last thought, have you looked at the original electronics to see what you can use? Chances are the original h-bridge in there is still just fine. At the very least, you may be able to re-use some components, or gain an understanding about what size transistors you need.