A toy car that drives around by itself

Updated: 2009-09-20, 2022-02-10


I wanted to make a small robot that could sense its surroundings and wander around by itself. I used a toy RC car, an Arduino microcontroller, and light and temperature sensors.


ToyBot In Action


There are more pictures, some with annotations, here.


I started out with this toy RC car from Kid Galaxy:

toy truck

I chose that car because it can spin in place by driving its wheels in opposite directions. That makes it much easier to steer than other cheap RC cars with crappy front-wheel steering, even though it can only turn in one direction.

I took out the radio-control electronics and replaced them with an Arduino microcontroller and an Adafruit Motor Shield. I added a few other parts:

Click here for a breadboard diagram of how the sensors are hooked up to the Arduino. (This doesn’t show the Motor Shield and motor connections.)

I had to remove the car body and hack up the chassis a bit, and here’s what I ended up with. (Click for an annotated version of the picture.)


Everything connected to the Arduino can be unplugged easily, in case I need to use the Arduino for something else (because I don’t have any spare Arduini). I made this easier by using some of the Arduino’s analog input pins as digital pins, for the LED and the bump switch. That let me plug most of the wires from the sensor board into one header block.

There are two separate power supplies. The 3 AA cells that originally powered the toy car are still used to run the motor, and a 9V battery powers the Arduino. I find this inconvenient. There are too many batteries to replace and the 9V doesn’t last very long. With the Motor Shield it’s usually a good idea to use separate power supplies for the motors and the Arduino, but I think a common supply would be OK with the one small DC motor I’m using. Unfortunately the 4.5 V supply for the motor isn’t enough for the Arduino.


I wrote an Arduino sketch to control ToyBot’s behaviour, using input from the light, temperature and bump sensors. Its basic behaviour is to drive toward an area of bright light. If it gets too hot, it heads for a shady area instead. (Basically, ToyBot acts like a cat.)

The behaviour rules are:

The LED activity indicator lights up or blinks to indicate what the bot is doing.

Here is the source code for the Arduino sketch that controls ToyBot’s behaviour.