Pololu Motor Driver 18v15: no current when connected

Hi all,

I’m trying to use Arduino to control the board and I’ve done it successfully with Dual VNH2SP30 Motor Driver. So I expected it would be very similar for 18v15 board. I read through all the necessary information listed under “description” tab but I couldn’t get my motor running. The power supply showed that there were voltage across but no current. I tried to vary the voltage within the maximum value but nothing happened. I only used DIR and PWM pins, as suggested in the description (under “Using the Motor Driver”). I left RESET, FF1, FF2 unconnected.

Here is my connections on logic side of 18v15 board:
5V to 5V pin on Arduino;
GND to GND pin on Arduino;
DIR to Digital pin 7 on Arduino (which only allows HIGH or LOW);
PWMH to PWM pin 9 on Arduino;

On Output side:
V+ to “+” of a single output DC power supply (30V 1A);
OUTA to a DC motor;
OUTB to a DC motor;
GND to “-” of the same DC power supply;

Here is my Arduino code. I held PWM high and DIR LOW. According to the truth table, it should make the motor turn forward but nothing happened. Any help would be appreciated!

int DIR = 8;
int Mono_PWM = 9;  //PWM1 connects to pin 9
int Mono_PWM_val = 255; //(25% = 64; 50% = 127; 75% = 191; 100% = 255)

void setup() {
  pinMode(DIR, OUTPUT);
  pinMode(Mono_PWM, OUTPUT);

void loop() {
    //Forward: PWM = H && DIR = L;
    digitalWrite(Mono_PWM, HIGH);
    digitalWrite(DIR, LOW);


You should not be connecting the 5V pin to your Arduino’s 5V line. The 5V pin on the motor driver is an output, and connecting it to your Arduino creates a short if the two nodes are at slightly different voltages. From the product page:

A good first step would be to simplify your setup. To start, for example, don’t bother using a PWM signal on the driver’s PWM pin; rather, connect 5V from your Arduino’s regulated power bus to the PWM pin and ground the DIR pin (and make sure the Arduino and the motor driver share a common ground). I suggest you disconnect your motor and use a multimeter to see if you get the appropriate voltages on the driver outputs. Try connecting 5V to the DIR pin and see if the driver output voltages switch direction.

Can you tell me about the motor you’re using? A 1A power supply seems very underpowered for the 18v15. Are you sure you’re not trying to exceed this current when your motor is connected?

- Ben


You also probably shouldn’t be connecting 30 V to the motor driver. The FETs on the 18v15 version can only handle up to 30 V max.

- Ryan

Thanks Ben, Ryan,

I use a DC motor with a nominal voltage of 12V and nominal current of 0.6A.
I connected PWM pin from the board to a Arduino PWM pin, DIR to a normal digital pin, GND to ground pin on Arduino, RESET pin to a digital pin. In the beginning nothing happened and then I found this trick: I specifically set RESET pin as OUTPUT and held it HIGH. It worked!!! Flawlessly! Really appreciate your help!