Problem with dual mc 33926

Good afternoon. I am trying to control two motors with gearbox, specifically these: 228:1 Plastic Gearmotor Offset Output
To do this, I use the Arduino Mega 2560 and the dual mc 33926. The problem is as follows:

To controller 5V DC voltage but they arrive just engines 2V, so that when want to be at a slower speed, for example 50%, the motors are not moving, as the voltage that reaches them is 0 ,3-0, 4V.

Where can be the problem? Can it be that you have to change the frequency at which it works arduino?

Or maybe the code that I use is not appropriate?

Then I attached the code if it helps.

Thank you very much.

[code]Arduino Code

const int M2D2 = 12;
const int M2IN1 = 28;
const int M2IN2 = 26;

void setup(){
pinMode(M2D2, OUTPUT);
pinMode(M2IN1, OUTPUT);
pinMode(M2IN2, OUTPUT);


void loop(){

digitalWrite(M2IN1, LOW);


The idea is to move sideways. If instead of putting 255 (which is 100% speed) put 80, the motor does not move.


What do you mean by “they arrive just engines 2V”? How are you measuring that voltage? Which version of the dual MC33926 motor driver do you have, the shield or the carrier? Could you post pictures of your setup?

If you have the dual MC33926 motor driver shield for Arduino, could you run the demo program found in this Arduino library? The picture below shows how the shield is wired to the Arduino. If you have the dual MC33926 motor driver carrier, you might try connecting the inputs in the same way and using the Arduino library.

- Jeremy

First, thank you very much for the reply.

I mean that the engines only have a voltage of 2V, instead of the 5 I enter from the power supply.

The dual mc 33926 is connected to the Arduino via a pcb designed by me.

Is there a connection that’s wrong? Should we put in the arduino software, a default pin?

Right now I can not try the demo because I have the material available, but next week I do without fail.

A greeting.

It looks like some of the traces on your board go between pins. What is the minimum distance of clearance on those traces? Could you post a picture of the other side of your physical board that shows the traces? It also looks like the motor driver might be connected incorrectly (it looks off by one pin). Is the driver on the board correctly?

Could you also try taking the motor driver carrier off of your shield, placing it on a breadboard, and making the connections to the Arduino with jumper wires to see if it works?

- Jeremy

Is not well connected but only for the photo, because I did not realize. As pictures of the other side of the plate, but now I have tomorrow and try to make a raise.

Anyway tomorrow I will try to connect the motor controller on a breadboard and see what happens, to see if the problem is on my shield.

Thank you.

Hello. I’ve been looking and I have discovered one thing. When I connect the motor without load, if you get ±5V depending on the direction of rotation, however, when I connect the engine, yet the assembled project (pulleys, strings, parts, etc.) that is loaded is when no you only get 2V.

Why is this? How to solve it? I need you to reach 5 V to regulate the speed with which it moves.

It sounds like you might have a power issue. Could you tell me more about the power supply you are using? How much current can it deliver? Could you also tell me about the motors you are using (e.g. their stall and free-run current)?

- Jeremy

The motors I use are these:

Solarbotics GM8 143:1 Gear Motor Offset Output

  • 6 V Operation:
    No-load RPM: ~ 78
    No-load current: ~ 52 mA
    Stall current: ~ 700 mA
    Stall torque: ~ 76 oz-in

As for the power supply is normal, controlled source of both voltage and current. I use the output having ±5V, but if I use the adjustable (at 5V) and increase the current, voltage increases engine just …

I do not know if you will see that the engines are loaded or empty, but I’ve never again to connect load and work well, while still loaded with 2V.

- Thanks.

It is really hard to understand what you are trying to say about how your power supply is set up. What is the maximum output voltage and current of your power supply? What do you have the current limit set to? Could you post pictures of your entire setup that shows all your connections and power supply?

- Jeremy

The maximum voltage is 5V and the current is 1A.

That power supply might not be powerful enough for your system. Are you powering the Arduino or any other devices from that power supply as well? Could you try using a different power supply that can deliver more current? By the way, we recommend operating that controller with voltages above 8V, as operation from 5 - 8V reduces the maximum current output.

If you still have problems after changing power supplies, could you post pictures of your setup?

- Jeremy

Thank you. I’ll try with another power supply. I have a 5V 4A, I hope it’s not too much current.

I will comment on the results. Thank you.

It sounds like you might be confused about how current works. The load attached to the power supply will draw the current it needs, if it is available. The power supply will only output as much current as the load draws; it will not force 4A through the device.

- Jeremy

When the voltage is 8V problems disappear, so I will use that voltage.

Thank you very much.