In a few months, I am planning to construct an Arduino robot with multiple sensors etc. I will use an arduino mega and a 4wd chassis like the one here: Chassis. The chassis uses 4 DC motors. I was planning to use a motor shield, but I realized that it only fits an Arduino Uno(not Mega) and it controls only 2 DC motors. What can I do to make all 4 DC motors move forward and backward? If I use a motor driver board that controls 2 motors, can I connect the 2 right and 2 left motors in parallel together and the control it through the Arduino?
You should connect Vcc 1(used to power on the chip) to 5V and Vcc 2 to a power supply that is needed to run your motors, Enable 1,2 and Enable 3,4 are used to enable the 2 sides of the chip and should be connected to 5V. Outputs 1-4 are the outputs to 2 motors and Inputs 1-4 are the inputs from the micro-controller.
Yes, you can actually do this, but you have to consider the current of the motors and the motor driver. For example, if you have 12V, 2 Amps motors, then you need a 2-channel motor driver that is able to output a little higher that 4 Amps (2*2 Amps) for each channel at 12V. You will need to connect each two motors on the same side in parallel to one channel.