Motor/power control problem

Other Hardware Motors, Mechanics, Power and CNC
1

Hi,
It's been several sessions that I can't solve this problem, I need your help please.

I want to control with a l298n motors drivers & an arduino UNO a RC car motor of a 14v.
I tested with mini motors and it works without any problem, but when I switch to a bigger motor, I just hear the effort slightly from the motor but it doesn't work like for the small ones.

Here is a video of the motors that work: mini motors work - YouTube
And the video of the motor that I want to make work but that does not work: the motor does not work - YouTube

The code is good
Battery used: AMP9037 12V-7Ah
Motor: Traxxas Motor Titan 550 Reverse 14.4V 21T 3975R

Do you have any idea where this is coming from please?

2

What does the motor's data sheet say about its stall current, which is the current required to get it moving. Is that within the L298's ability?

3

Thanks for your answer!
I did not find this information but I know that the L298n can accept up to 46V

4

With a generator I tried and with 5v only on the engine it worked too well but when i use l298n I don't know why it's not working

5

I asked about current though.

It's possible that the L298 can't provide enough current.

Use your Ohmmeter to measure the resistance of the motor, and use Ohm's Law to calculate the current, given the resistance and the voltage.

6

Judging by the videos you're in a great lab at college or similar: surely you have tutors or lab assistants or TAs or lecturers to turn to?

7

Okay I think the problem comes from the l298n. i see now its overheating, do you know which component can i use ?

8

Yes we are in a college, we have a teacher who tried with us but even him don't know why it doesn't work lmao

9

It's impossible to specify components without knowing the facts, and the crucial fact you're missing is the motor's current draw at stall (ie at startup).

You need to know that- see #5. What's the resistance, and what current does that calculate out to?

Then look at a list of drivers such as those at Pololu, comparing your requirements with each board's offering.

10

Hmm okay thanks,
here are the measurements we were able to collect. the voltage decreases a lot at the exit of the l298n

measures
measures1920×3106 360 KB

11

You need to know the stall current....

  • With the motor disconnected from the circuit, measure the resistance of the winding and apply Ohm's Law. (I'd do it this way.) OR...

  • Measure the current if your meter has a current setting, by breaking the circuit and measuring the current across the break.

12

like that?

image
image438×584 63.5 KB

12/5= 2.4A

13

Which if my memory serves me is over the L298's current limit of 2A.

15

Okay thanks ! I looked on the internet and it seems very difficult to control a motor of 2.4A, this l298n is not enough. do you know what similar component I can use please ?

16

what do you think about that one ?

17

That's a 21 turn motor, the stall current will be massive (think 50A or more even), its designed for use with a LiPo battery and ESC suitable for a high current RC DC motor. You need a suitable RC ESC to drive it.

18

oh :confused: so the link i sent doesnt work for my project
when i use the motor on a generator i dont need 50A to start it, i dont really understand

19

Stall current is the current that flows if the input voltage is held at the nominal value with the rotor locked. If you connect a motor direct to a DC supply thats able to handle that current, that's the current that flows momentarily at start up, due to resistance alone.

If the DC supply cannot deliver that high a current it will overload briefly as the motor starts and the voltage will dip (may SMPS don't like this and will reset if you try).

In high power motors you actually never want full stall current to flow, but the startup current is always going to be large (certainly beyond a lowly L298) for this type of motor as it basically a few feet of copper wire direct between the terminals until its spinning fast enough for back-EMF to limit the current.

A suitable ESC will handle the ramp up of PWM duty cycle needed to start the motor in a civilized manner (perhaps only 10--20A spike then?).

[ BTW don't trying locking the rotor in a motor like this, ESC's typically explode if you do this as they are not engineered for such abuse ]