I’m new to Arduino and am trying to build a plant watering system without much knowledge on the subject. But my water pump is not working as I expected it to.

I wanted to keep it simple so I bought a Arduino Motor Shield for my Arduino Uno R3. I’m using a motor rated at 3-9V (motor is shown below), I’ve tried two different DC adaptors plugged into the power supply port on the arduino, 12V 1.5A and 12V 2A, even though the motor is rated at 9V, I’ve read that I need a 12V adapter to power the motor shield. http://www.mabuchi-motor.co.jp/cgi-bin/catalog/e_catalog.cgi?CAT_ID=rs_360sh

The first problem is If I run the motor at full speed, analogWrite(3, 255), it sounds like its going to explode, so I’m trying to run it at a lower speed. But If use values anywhere below 170 the motor will not run and will only make a beeping sound.

Secondly, regardless of the PWM value I run the motor at, the chip gets very hot very quickly.

My question is, why can’t I run the pump at lower PWM values, and why is it getting so hot? If I bought a 12V water pump and used the same setup, would I not have any of these problems?

EDIT: an update... it seems to basically work now. i have a feeling it wasn't working great because I was previously using a powerbar

It will run on max power PWM(255) for about a minute, and then stop working, which is okay. It will stop and then the motor shield lights will start blinking. Does anybody have any guesses what is happening? The motorshield chip is a little hot, so overheating is a possibility. Or is there not enough current ?

video https://www.youtube.com/watch?v=xdxf3f_Svqs

void setup() {

//  //Setup Channel A
  pinMode(12, OUTPUT); //Initiates Motor Channel A pin
  pinMode(9, OUTPUT); //Initiates Brake Channel A pin

void loop(){
  //forward @ full speed, A
  digitalWrite(12, HIGH); //Establishes forward direction of Channel A
  digitalWrite(9, LOW);   //Disengage the Brake for Channel A
  analogWrite(3, 170);   //Spins the motor on Channel A at a speed. approx 90 is min


  digitalWrite(9, HIGH); //Engage the Brake for Channel A


  • I’ve read that I need a 12V adapter to power the motor shield. That's incorrect; the product page says 5V to 12V.
    – Gerben
    Mar 20, 2016 at 19:42
  • the chip gets very hot very quickly - which chip?
    – Nick Gammon
    Mar 20, 2016 at 19:54
  • Would that be the voltage regulator chip by any chance?
    – Nick Gammon
    Mar 20, 2016 at 22:22
  • @NickGammon it is the main L298P chip
    – Nicky
    Mar 20, 2016 at 22:52
  • Of course it sounds like it's going to explode if you're powering a 9V motor with 12V. This could cause a much greater current draw than you would expect as the relationship between voltage and current is unlikely to be linear once you go out of the manufacturer's specifications, which is why the driver gets hot. Mar 23, 2016 at 8:16

1 Answer 1


Regarding your motor just making high pitched noise (beeping) I would say that you are not supplying enough power to your motor for it to pull in the load and get rotating, you might try to first get it started by a higher power setting (PWM) and then when it's running see how far down you can set it before it stalls (stops).

I don't belive a 12V pump would work any different.

As to the motor and L298 chip getting hot, this is sort of normal and in some cases would require som way of dissipating this heat. A heatsink might be an option.

If you were to overheat the L298 it will shut down before being destroyed (it should).

  • Okay thanks, does that mean I should supply more voltage or current ? It just seems strange considering the water pump is rated at 3-9V
    – Nicky
    Mar 20, 2016 at 22:54
  • 2
    Neither, By power you have to take into considerment that you are using PWM. That means that if your motor at 12V would draw lets say for ease of calculation 1A at 100% pwm it would draw 12W (Watt) by lowering your PWM ratio to 50%, your motor will still draw 1A at 12V but only half the time.
    – Hans Neve
    Mar 21, 2016 at 12:34
  • The motor runs smoothly and reliably when I connect it straight into the VIN pin using a 9V adapter. But when I drive it through the motor shield problems occur. Ideally I would want to drive the motor shield/motor with a 9V power adapter so that I can run the motor at max PWM (255), but there isn't enough power if I do that because the motor shield also needs power.
    – Nicky
    Mar 22, 2016 at 0:49
  • I thought to myself, maybe I'll just run the motor at max power (12V) for the project, I don't need it to be on that long so it's ok. But as I was trying to test that out, the motor stopped responding, the lights on motor shield were blinking and I could hear a ticking sound. So…… is there any solution to this apparent "electrical noise" ?
    – Nicky
    Mar 22, 2016 at 0:49
  • Check voltages at 100%, you might have burned the motor.
    – Hans Neve
    Mar 23, 2016 at 18:59

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.