L298N motor driver not providing enough voltage to motor?

I have a L298N motor driver and I am trying to control my old RC car's rear motor.

My circuit is pretty basic - Arduino with 2 digital pins controlling direction and 1 PWM for the speed, 12V adapter plugged into the L298N's power source and a motor connected to the L298N motor output pins.

My issue is that when I power the motor directly from the 12V adapter - it runs perfectly fine. However when I try to power it via the L298N it just doesn't get enough voltage through.

I've measured the output voltage with a multimeter with the speed set to max (255) and it's barely 0.15V - enough for the motor to make some noise but not enough to make it spin.

What can I try to resolve this or at least troubleshoot it better?

Well the 298 does drop almost 5V at high current but this is a bit extreme…

You didn’t mention connecting the logic supply to the 298, nor the common ground. They are both shown in this schematic…

l298 arduino.JPG

Common ground! That was it. It's perfect now.


Twinsmaker: Common ground! That was it.

Glad to help. I assume you figured out why it's needed?

Unless you have a pressing reason to use a 298 (like you got a boat load of them for free) you might consider a more modern motor driver chip that doesn't throw 5 of your precious volts into the air as heat. I have the 2130 from this list, for example.

The one you listed is $5 and I got my 298 for $2.5 so that’s 2 times cheaper.
Also the fact that it doesn’t require any soldering is a big plus for me regardless of the size (for now).

Could you clarify what do you mean by “throwing 5 of my precious volts into the air” though? I’m powering it via 12V power adapter.

Twinsmaker: Could you clarify what do you mean by "throwing 5 of my precious volts into the air" though? I'm powering it via 12V power adapter.

The technology of the 298 causes a voltage drop of 2V minimum, so the most you'll get at the motors is 10 if you start with 12. But at higher currents, around 2A iirc, it wastes almost 5, leaving you with 7V.

Apart from leaving you with fewer volts than you would like, you need to manage the heat dissipation somehow. That's why 298 based shields like this have a huge heatsink.

Thanks for the info, after understanding the problem better I might get one of the boards you've linked here.

Also, I saw that some of the motor drivers in the list come with a small heatsink, but it's not attached to the driver by default. Is it hard to put it on and does it require soldering/gluing/sth else?

There is special heat sink glue, or tape, that do the trick.