Motor Driver Error - Simple Motor Controller 18v7

I’m connecting Simple Motor Controller 18v7 to my laptop with motor connected. After some troubleshooting errors. Now i have “motor driver errors”. I don’t really know how to fix this, could any one please help me?
I’m using 2 AA battery connecting to 2 pins on the controller, and connects 2 other pins to a DC motor (1.5-3V range). When i took out the dc motor with batteries, it works totally fine.



It sounds like you are not supplying the Simple Motor Controller with a sufficient voltage. You should supply it with between 5.5V and 30V. It sounds like you might have a motor that is only rated for 1.5V to 3V. If that is the case, you could effectively limit the voltage supplied to the motor by limiting the duty cycle of your PWM signal.

If you are still having trouble after increasing your supply voltage, could you post pictures of your setup that show the solder joints and all connections?

- Grant

Thank for the response.

So if my motor is only rated from 1.5V-3V. I can’t supply 6V right?
That means I have to change to another motor to have a voltage at least 5.5V?
By the way, I thought the motor controller is supplied power through the mini usb cable? isn’t it?


You can still supply 6V to the Simple Motor Controller even if your motor is rated for 1.5V - 3.0V. Limiting the duty cycle to 50% with a 6V power supply would effectively supply 3V to the motor.

The SMC cannot drive a motor while only powered by mini-USB. The mini-USB connector only supplies power to the motor driver’s logic; VIN supplies power to both the motor and the motor driver’s logic.

- Grant

Hi Grant,
Thanks for the reply, i will definitely try that. But how do you limit the duty cycle to 50%, and is it okay if you don’t do it?
However, I have a question about the speed (rpm) of the dc motor. I’m making a spin coater to spray a layer of photoresist on a wafer. If I want the motor to spin exactly at 4000 rpm. And when we spray the chemical on top of the wafer while the motor spinning, it would affect the speed of motor when there is a load. Is there any way the SMC can detect the load weight, and give feedback to the motor to keep it spinning at the original speed 4000 rpm even if we spray some chemical on it (add load to the motor)?

Thank you very much!

You can limit the duty cycle on the Simple Motor Controller by changing the motor settings in the Simple Motor Control Center. The setting you will want to change is the Max. Speed. You can read more about this setting in the Simple Motor Controller user’s guide, which can be found under the “Resources” tab on its product page.

By the way, to keep the speed of the motor constant under varying loads you would need some kind of tachometer feedback, and the Simple Motor Controller does not have built in support for feedback. To process the feedback, you might consider adding a microcontroller or using one of our jrk motor controllers.

- Grant

Do you have any suggestion with the microcontroller for feedback?
It seems like I need to buy a SMC with feed back. Could you recommend me one?

I need to build a spin coater quickly asap, and the requirements are bellow:

  1. be able to input the speed range from 500 rpm- 5000 rpm (need to be precise)
  2. be able to input the duration (time) of the spinning
  3. when we have the load, and the chemical starts dropping off on the layer, the load weight will be varied, we want the feedback to correct this deviation and maintain original speed as we inputted

With those requirements, can you recommend me a cheap and easy-to-use one? And do i need an external battery or a power supply for it?

Also, is there a way that I can return my old SMC and buy this new one instead? IF not, could you please help me to get a discount one?

Thank you very much,

Though our Simple Motor Controllers do not support feedback, you could still implement feedback while using the Simple Motor Controller in your system. You might consider having a microcontroller process the feedback and send commands to the Simple Motor Controller to drive the motor. For a microcontroller, you might look into an Arduino, as they are generally easy to use, and there a lot of resources out there for them. We do not accept returns on opened items, but if you decide you want to use a different controller of ours, you could email us directly and I might be able to get you a small discount.

- Grant

Hi Grant,
I’m not good at programming with microcontroller. Therefore, I guess I will need to buy a jrk controller. Which one do you recommend me to buy to accomplish the tasks I described above? And do you know what exactly I need to buy to perform those tasks? (the jrk controller, motor, and external battery right?) I don’t want to waste my money this time again, so I really need your help to determine exactly what I need to buy so that I can complete the required tasks of the spin coater on time?

Thank you.

Also, which email can I send to get a small discount as you said?


I cannot design your system for you or tell you everything you will need for your project. You might be able to use the jrk in your project, but please note that it is not a plug and play device, and it would need to be properly configured for PID control. I suggest reading the jrk user’s guide to see if you think it is something you are comfortable doing.

If you decide you do want to use a jrk, you can contact us at to ask about the possibility of a small discount.

- Grant

Hi Grant,
Thanks for the advice. I check Jrk controllers, and there are many of them. If I want to operate a DC motor with 12V or below, which jrk controller would you recommend me the best with less expensive?

Thank you very much

Both versions of the jrk motor controller can operate at 12V. It is up to you to determine which is appropriate for your application.

- Grant

Hi Grant,
I got your discount of the jrk controller. However, I’m trying to use Arduino to control the feedback with the Simple Motor Controller 18v7. If i can’t make it work, i will then buy the jrk. I would like to ask for your advise, Do you think I need a motor driver to control the feedback with arduino? Or the Simple Motor Controller itself can be interacting with the Arduino for the feedback?

Thank you for your time!

As I mentioned in my previous post, you could use the Arduino to process the feedback from the encoder and send commands to the Simple Motor Controller to drive the motor based on that feedback.

- Grant