The Arduino motor shield was purchased from NKC Electronics. For about $11.00 it’s a decent controller based on the L293 motor driver chip and able to produce an output of up to 2 Amps all together. It comes as a kit and takes about 30 minutes to assemble. It works with the Arduino as a shield, attaching to the output pins as a daughterboard and eliminating the need for wiring. The controller can be used without an Arduino, the shield accepts power for both the logic and the motors through separate pins.
It’s capable of driving the two DC motors forward and backward, and the chip can be enabled or disabled by setting the chip high or low. The motors can be controlled independently and the board has a pair of LEDs that show motor operation and direction. PWM allows the controller to vary the speed of the motors.
The board isn’t particularly robust; you can blow one up without a lot of effort. Stalling or shorting the motors can burn it up in a wink and short circuits on the output will definitely crater one or both of the L293 ICs. I find it best to power the motor controller separately from the Arduino. Instead, create a power supply of around 9 volts and use a 7805 to create the voltage required to drive the controller logic and unregulated power to drive the motor. It is wise to put a heat sink on the L293; I use heat conductive glue to affix a DIP sink on the chip.
Sadly, the website that contains the assembly and usage instructions has been listed as an attack site by a number of watchdog agencies and so I cannot recommend using this controller unless you can find clean instructions elsewhere. The records show that the instruction site installs malware that damages your computer and destroys your programs and stored information. It also doesn’t speak well of NKC to allow the problematic condition to persist. They have had months to correct the situation and have failed to do so. I gave consideration to not talking about this little controller but since I have put more than 10 of them to use and had decent luck with them. You will see the brilliant red of the controller in a number of the photographs you’ll see here. Those who have electronic skills won’t really need instructions; I used them the first time and assembled the rest by memory quite easily.