Motors for RC Car

My friend, who has a 3D printer, and I are trying to build a cheap RC Car. All we need to buy are the motors and what we need to connect the motors to the Arduino, and we can 3D print the rest. I’m wondering what kind of motors are normal and cheap for an RC Car and can be hooked up to an Arduino. So I need what motor, and what do I need to hook it up to the Arduino. Will I need to change my power source? If so, what do I need to use to power 4 motors.

How big, heavy is this car? How fast do you want it to move?

The size will be proportional to whatever motors we choose. I don't really care about speed as long as it's super slow. I'm worried more about cost than I am about effectiveness.

Well, if your car is tiny, you can just attach the motors directly to the wheels. If it's larger, I would recommend these.

My friend, who has a 3D printer, and I are trying to build a cheap RC Car. All we need to buy are the motors and what we need to connect the motors to the Arduino, and we can 3D print the rest.

Use a continuous rotation servo to drive one of the wheels.

CantSayIHave: Well, if your car is tiny, you can just attach the motors directly to the wheels. If it's larger, I would recommend these.

This seems like it might do. We're going to use some little Mecanum wheels (we hope) so we can just 3D print something to mount the wheels we're using onto that motor. For that motor, do I need some kind of motor shield? Also, what about a power source. We're going to need to be powering four of those if we use it.

The order to do things is this:

1) Decide on the mechanics 2) Size the motor 3) choose a motor driver / shield

So first decide on the mechanics, from that you know the torque and power requirements, then you can choose motor and gearing, and only then do you know what the driver electronics need to be.

So assuming that I am using four of http://www.amazon.com/Geeetech-Smart-Wheel-arduino-project/dp/B0081C5B80

What motor shield and power source do I need?

Well at 3V those motors have 0.08Nm or torque at 170 rpm (18 rad/s), or about 1.3W in theory. That current level (0.25A stall) won't be a problem for any motor shield, you can run the motors at higher voltage for more speed and power.

Note that the darlington-based shields (using L298 or L293 chips) are going to lose about 2 to 2.5V, so aren't great for low voltage use as you throw half of it away and get hot. However probably not too hot with such small motors.

So http://www.arduino.cc/en/Main/ArduinoMotorShieldR3 can do two motors, can I do two of these on top of eachother?

A Note: I'm 16, and I'm just getting into Arduino. I am a programmer at heart and I suck at electrical, so I have no clue and I need things to be explained as much as possible. Thanks

Actually I think that http://www.sainsmart.com/sainsmart-l293d-motor-drive-shield-for-arduino-duemilanove-mega-uno-r3-avr-atmel.html can do four motors. Can anyone confirm? Also, how many batteries would I need to power this?

For four motors would you recommend: 4 Batteries: http://comingsoon.radioshack.com/radioshack-enclosed-4-aa-battery-holder/2700409.html#.VWtzuE_BzGc 8 Batteries: http://www.amazon.com/Battery-Holder-Standard-Snap-Connector/dp/B000LFRTIK Or something else?

?

Batteries have a current capability and a capacity - you need to know the total current draw and the length of time you want the batteries to last, we can't guess the later and the former depends on what else is being powered and how heavily the motors are loaded (may require some current measurement to be sure).