First Project

[Andy M]

I'm very new to microcontrollers, but I've just finished assembling and programming my first project. (Well, second one, if you count a blinking light)

It's a traction control system for my RC car. It works by intercepting the signal that my receiver sends to my ESC and scaling it down based on the relative speeds of the front and rear wheels on the car, which are measured by photo-interrupters and mouse encoder wheels attached to the front and rear differentials. The car was 4WD, but I removed the driveshaft connecting the front and rear gearboxes. I also identified the neutral point and made the device only work in forward.

My circuit also draws it's power from the battery eliminator circuit in the ESC. This was problematic because I waaay underestimated the motor's ability to cause voltage sag, which obviously causes problems.

Pictures and/or video to follow.

[AndyP]

Andy, I would be interested to hear how you get on with this one because I thought about doing the same thing before, but never started it.

Its possible that you could also incorporate ABS into the same unit by applying reverse motor current when a braking signal is received, and pulse the current if the wheels are seen to lock by the photodiodes.

I had exactly the same problem with voltage sag on an ESC that I build for a twin motor monster truck (TXT-1). What I did was to go out and buy one of those 1 Farad memory retention capacitors and have this charged by the Nicad battery. It supplied power to the PIC only (not servo's) by way of diodes etc. The thing to watch is that your PIC doesn't have to source much current to other things, e.g I was using the hardware PWM module to control motor speed.

Let us know how you get on.

Andy P.

[Andy M]

Andy,
Hmmm... Perhaps the reason I didn't have to go to the same extreme as you is because my circuit is powered by my Futaba ESC, which also powers the (Futaba) receiver and steering servo. The battery eliminator seems to be pretty robust, barely dipping below 6V.

I built the system this way so that I could easily put it between the receiver and throttle servo of a nitro powered car.

I definitely need to shoot some video of this car for you! It worked out EXACTLY as I planned. Version 2 will have a couple of 25 turn trimmers for tuning the TCS delay and wheelspeed differential values for different surfaces without reprogramming.

-Andy