We have an RC car which we want to modify to be made of awesome.

Email chris [AT] tinkersoc.org to ask to be added to the project-rccar mailing list if you want to get involved!

* - Plus some VAT & Delivery

Other components

• Arduinos (we have many of them)
• Microphone (MEMS?)
• GPS module (Chris has one)
• LM35 temperature sensors (there are plenty in the lab)
• LDRs (also plenty around)
• Speaker/Buzzer?

• Adafruit Motor Driver Shield

• 1366570 L298HN - OP AMP, DUAL FULLBRIDGE DRIVER, 298
• 4620902 HEAT SINK, DIP, GLUE-ON
• 1217304TERMINAL BLOCK, PCB, 4WAY,1

• Arduino XBee Shield Empty
• 1 mile range Xbee module

For revision 1, we're going to try to keep the stock motors and gearboxes. We will, however, add our own motor controller and power source rather than trying to modify the existing circuitry. We need to design this board so that it can drive the motor. At best guess, I'd say we need to make it able to handle 2A peak. Our power supply will be a 9.6V NiMH battery.

In later revisions we can try to replace the motors with something a bit more hefty, so that it can handle the extra weight we will be adding.

After investigation on 09/02/2010, it seems that there is one beefy motor at the back which drives the rear wheels and the propeller. There's another mysterious servo at the front which does steering - except it's got 3 signal wires. Further investigation is required.

I suggest driving the motors using a Allegro A3953 as this does everything we need.

UPDATE: See TinkerSoc Motor Driver Project

Initial we are going to use Zigbee for communication to the car, because it is cheap and relatively easy to work with.

Other communication system we would like to look at are

• GSM
• WIFI
• GPRS £89 GPRS module

• http://www.technobots.co.uk/
• http://www.sparkfun.com/
• http://www.rapidonline.com/
• http://www.farnell.com/
• http://www.coolcomponents.co.uk/

We took apart the main steering assembly, and found at the heart of it this:

The DC motor powers the gearbox, which turns the shaft around. An endstop encoder is attached to the shaft, which turns around. When the output shaft is in the “left” position, it connects the white and green wire together. In the left, the white and purple wire are connected. Here's a shot of the encoder board.

So basically, the control logic will drive the DC motor in a given direction until it hits one of the endstops. It's essentially a 3 position servo. When it's not being driven in any direction, the spring in the assembly (not shown) will return it to a central position.

Great. Well, not so much. It means having an extra motor driver. We will replace it with a real servo which will do the job far better (and give us better control of steering).

We took apart the main drive motor and gearbox, to find that one of the small cogs in the gearbox had snapped (presumabley due to over-torque). Possibly solutions are to replace the gears in the gearbox (possibly change the gear ratio whilst we're at it), or to replace the entire assembly with a couple of gear-motors.

• motordriver