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Topic: Transformation of old RC car into wifi car - problem with motor and H bridge (Read 652 times) previous topic - next topic

Domix

Hi,

I wanted to transform an old RC car to a wifi controlled car. So I have connected the two motors from the chassis of the car to this H bridge L298N and a NodeMCU. The front motor is responsible for steering and works good. But the motor in the back, which moves the car forwards and backwards gets only 0,6 V while the front motor gets 4 V. And this is the problem. On every output of the H Bridge the back motor only gets 0,6V, but when I connect it directly to a battery it works without any problems. Also any other motor I have checked on the board works well on any of the two outputs. So everything is working like supposed but not together. Taking another motor for the back motor would be kind of complicated because the motor already has the gear to power the two wheels, which would not fit any of my other motors.

Does anybody has an idea why the back motor doesnt work with the H Bridge?

Thanks


Domix

The schematic is really simple. A nodeMCU is connected to a L298N H-bridge, which is connected to two small dc motors.

slipstick

It sounds like your "back motor" is trying to draw too much current for the L298N to cope with. Or maybe whatever you're powering it with can't provide the needed current or voltage.

Since you've given no details of the motors (small dc is not a useful specification) or the H-bridge or how everything is connected or powered that's the best I can do.

Steve

zwieblum

What's the voltage of the batteries? Your L298N board needs at least 7V to work propperly.

Domix

It sounds like your "back motor" is trying to draw too much current for the L298N to cope with.
If this would be the problem, how could I solve it?
Also i have forgot to write this: If I connect the back motor directly to the power supply, which I use for the car, the motor works well. It really only does not work, when connected through the H-bridge.
I have no info on the motors, there is no number printed on them.


What's the voltage of the batteries? Your L298N board needs at least 7V to work propperly.
The voltage of the battery in the car is 6V. When I use other motors in the car it all works but then I would lose the gear so it would not function as a car...

slipstick

You could try a better motor driver. The L298N is old and inefficient and can only handle about 1.2A.

You seem to have a multimeter so, if it can measure current, check the current of that motor when it is connected directly to a battery. Very briefly (a second or two only) hold the wheels so they can't turn. That gives you the stall or maximum current. Then you can choose a motor driver that can handle at least that much current. Pololu have a good range of modern motor drivers https://www.pololu.com/category/11/brushed-dc-motor-drivers but there are plenty of others available.

Steve

Domix


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