Problem using MC33926 motor driver to power a motor

Robotics and electronics discussion Software and microcontrollers
1

Hi,

I am currently trying to use the motor driver MC33926 to power a brushed motor but for some weird reason it is not working even though the motor driver seems to be outputting some voltage at OUT2. Here is my setup:

VIN (on the left of the motor driver) - +12V from a battery that is delivering roughly 1.5A
GND (on the left) - -12V from that same battery.
OUT2 - hooked to the brushed motor.
OUT1 - hooked to the other end of the brushed motor.
VIN (on the right of the motor driver) - left alone since it is internally connected to the left VIN
GND (on the right of motor driver) - left alone since its interally connected to the GND on the left
Vdd - 3.3V from my microcontroller
IN2 - LOW (I wired it to the GND pin on this motor driver)
IN1 - HIGH (I wired it to the Vdd pin on this motor driver)
PWM/D2 - I wired this pin to a PWM output pin from my microcontroller
PWM/D1 - LOW by using a jumper
SF - not used
FB - not used
EN - HIGH
SLEW - HIGH
INV - HIGH

I did this setup similar to the example that pololu wrote on MC33926’s product page but it does not work. Is there something wrong with my wiring? I tried changing the INV pin LOW/HIGH and the IN2 IN2 to LOW/HIGH etc but it still does not work. I know for a fact that my brushed motor is not broken because when i hooked that same 12V batter directly to the motor, it runs perfectly but when I put it through this motor driver, it does not work. Can someone with experience with this motor driver help me please because my project is due soon! Thanks in advance.

- Tom

2

Hello.

One problem I notice with your setup is that you do not have a common ground between your microcontroller and your motor driver, which means that your Vdd pin is not 3.3V relative to the ground on your motor driver. If you connect ground from your microcontroller board to the small ground pad, do your problems go away?

- Ben

3

hey Ben, sorry I did not fully write out my complete setup during my earlier post but I did grounded my microcontroller and the 12V battery with the motor driver at the GND pin on the left side (gnd above OUT2) of the motor driver but it still does not work. Am I also suppose to ground the GND pin on the right side (the gnd above Vdd pin) of the motor driver also?

- Tom

4

Hi Tom,

I’m following up on our conversation on the phone. You said that SF is going low, this is probably because you are getting an overcurrent/overtemperature fault. What is the current draw of your motor at 12V?

- Ryan