Anyone have any idea of what motor I should buy?
Only the manufacture that designed and built the motor is in a position to develop and publish a true datasheet for a specific motor. A given 'shop' may be able to perform their own measurements and give you an estimate of the key motor parameters, but I wouldn't count on it.Remember, measure twice cut once.Lefty
The type of motor for a 1/10 scale RC vehicle like that one is called 540. 540 refers to the diameter and bolt pattern on the face of the motor. I would get a slow motor if possible because that car could easily be too fast, and make it too hard to operate.
Ok, what is stopping the "shop" from linking that data sheet?
The link you gave is a 2 channel motor control. It is more complex then you need and would take more programming skill to use it. I don't think it is the best choice for you. You could use an electronic speed control "ESC" with reverse designed for remote control cars. The operate with the same pulses that servos do. It will simplify the code and it will easily handle the motor for your car.Traxxas uses a motor made by someone else. For what they use it for, they are not concerned with precise amperage. They make their parts good enough to withstand much more than required. I started to look for an ESC for you but, brush motor ESCs are harder to find than I expected. I am sure they are out there but, it will take some looking.
According to the graph picture in your sparkfun link, the voltage should go to minimum with nothing in front of the sensor. Maybe, you are getting interference from something else? Maybe you need some blinders "shields" between the sensor and beam output.
You mean I would get some interference from distracting light, I could try it in another room.
I read the datasheet before and it said something about getting a by-pass capacitor of 10?F or morebetween Vcc and GND near this product. Could that be the problem?
Adding the capacitor would at least eliminate that possibility. It is hard to say if that is the cause or not.