Erratic behavior SEEED Motor Shield

first of all, I apologize for any difficulty of understanding my thread since this is my first type posting my question.

I am trying to use potentiometer to control my sumtor 42HS4013A4 Bipolar Stepper motor’s speed using the Arduino and the SEEED arduino motor shield v2 but the motor and the motor light indicators on the Seeed motor shield behaves erratically (the behavior of the motor and the indicators are directly related)

You can see the picture of the setup and the codes in my attachment.

  1. If I use the usb cable to power the arduino + arduino shield + the stepper motor, the motor only runs accordingly to my code when I bend the cable end near the arduino. If it is not bent, the motor light indicators fine but motor cannot turn (it seems that the power to the motor is not sufficient if the cable is not bent)

  2. If I use the external power (at 9V) hooked up to the seeed motor shield to run the circuit, the motor light indicators on the motor shield are fine at high potentiometer (analog) value (but the stepper motor turns very crooked). At low potentiometer(analog) value. The motor shield runs for 1 second then turns all motor lights indicators off (while the power indicator on the shield stays on). This behavior repeats in a cycle until I increase the potentiometer (analog) value.

I at first thought that the problem was due to a low quality arduino. Yet the problem remains the same after switching to 2 other arduino boards.

Seeed_potentiometer_controling_speed.ino (673 Bytes)

Bending a cable should have no effect. Your cable may be broken or you have a bad connection in the plug/socket.


Post links to the datasheets for your motor and for the motor shield you are using.

Have a look at steppper motor basics.


Never power a motor from USB, you risk damaging something expensive like your computer. THis gives the information about the motor shield I am using This gives the information about the motor light indicators of the motor shield. The v1 and v2 motor shield have the same motor light indicators. This is the information about the stepper motor

I understand that there could be the problem with the cable. I would doubt there is any problem with the arduino plug because I have replaced 3 of them.

However, could you help me explain the erratic behavior of the arduino shield + the stepper motor when I use the external power supply plug in the shield. The problems occur at all voltage from 6 to 12


As far as I can see your motor requires a current of 1.3 amps. That is far in excess of of the 0.5 amps (max) that a USB connection can provide

That motor shield is a very poor choice for driving a stepper motor. Have you read stepper motor basics?


Yes, I have read through your post, but I assume that, since the shield working current is 2.2 amp. It should be able to run the arduino without any problem.

Can you explain why this is a poor choice?

You should not be using a motor shield to run that motor, it needs a current-controlled chopper driver like A4988 or DRV8825. Low impedance motors like this are for current-control, not voltage control.

since the shield working current is 2.2 amp

This is actually nonsense, but your experience is quite typical. The manufacturers, as well as the shield manufacturers, have been misrepresenting the current-handling capability of the L298 chip since its inception. See for example

You will have much better luck with a modern motor driver board using the A4988 or DRV88x5 chips. Pololu is a good source, and they support their products.

e2738729: but I assume that, since the shield working current is 2.2 amp. It should be able to run the arduino without any problem.

As I and others have said, a h-bridge is not appropriate for a stepper motor whatever the marketing guys might say.

But even if it was, where is the 2.2 amps going to come from if you only have 0.5 amps from a USB connection ?


Thank you very much. I will try the Chopper drivers then

I will try the Chopper drivers then

With a separate motor power supply capable of supplying a couple of amperes, of course.