Should I use motor driver or Motor driver shield?

Question

I want to run 4 microgear motor for an RC car with Arduino. Should I use L293d motor driver/L298n motor driver/L293d motor driver shield?? I am using N20 microgear motor with following rating: 6 V, 200 RPM and 120 mA with no load, 40 oz-in (2.9 kg-cm) and 1.6 A at stall.

Answer 1

The right driver module or shield depends on the motor. Do you know the voltage and the stall current of the motors ?

The L293D uses bipolar transistors for the output stage inside the chip and can only drive 600mA. It has a large voltage drop: the motor gets less voltage than the power voltage applied to the driver. Therefor it can be used with small 12V motors, but it does not work very well with 6V. The L298N also uses bipolar transistors and also has a large voltage drop. A mosfet driver like the DRV8833 works better with 6V, because it has a low voltage drop.

In small RC toys with four AA batteries, sometimes a H-bridge is made is transistors instead of using a special driver chip.

The very cheap motor shield with two L293D chips (originally designed by Adafruit) can drive four motors, but it uses many pins.

Bottom line: Everything depends on your motors. I suggest to use a mosfet driver.

Answer 2

The key differences between the L293D and the L298 are these:

• the L298 supports higher currents (up to 4 A with proper heat sink), the L293D is limited to 600 mA
• the L298 has a higher operating voltage (up to 46 V), the L293D is limited to 36 V
• the L298 is a dual full bridge driver whereas the L293D is a quadruple half bridge driver

Ok, what's the difference of two full bridges vs. four half bridges - it somehow sounds to be equal? In fact, when driving a DC motor that requires to reverse the polarity to reverse rotation a full bridge is required. This full bridge could now be provided by either of the L293D (two half bridges) or the L298 (one full bridge). If you on the other hand want to drive a four winding stepper motor (two phase bipolar) the L293D would be more helpful as it could drive two such steppers (using two separate half bridges) whereas the L298 would need to use both its full bridges and could therefore only operate one such stepper.

But since steppers are not part of this question this difference does not really matter and you could pick either chip with respect to the required current rating. A stall current of 1.6 A would be a serious problem for the L293D:

Peak output current, I_O (nonrepetitive, t ≤ 100 μs): 1.2 A

Whether to use the chip or a driver board or a shield, to be honest, is mainly personal preference. Shields and driver boards come ready-to-use on a pretty printed circuit board which is probably their main benefit.