A query regarding motor pwm using l298n driver and Pico/Arduino

Projects General Guidance
1

I tried controlling speed of DC Bo motor using an l298n driver. For pwm I used pi pico w and an Arduino Uno R3

I used a multimeter to measure the voltage at which the motor would start initially from rest.

For the Pico it was about 1.7 1.8 volts
For the Arduino it was about 1.1 volts

Note that the Pico has an output of max 3.3v 16mA on gpio pins and for arduino uno this number is 5v 40mA

My query is....does this mean PWM control gives me a smaller range of speeds if I use the Pico..? From what I understand..yes..but..I'm not sure. Any ideas ?

Thank you

2

No - it's the pulses / pulse widths.
If the pulse voltage is sufficient for the L298 as a valid input then that's that.

3

A VOM is not a very accurate device under certain conditions, use a scope for accurate data.

4

What frequency did you use on the pico?

5

The pwm Freq on the pico was 5000 and on Arduino was 1000.

6

That may explain it

7

I'm going to try n measure the rpms to be certain about my query...but as for the frequency differences..a higher frequency just means a finer control over the voltage right..?

The speed of the motors depends on the voltage level supplied to the enable pin, a high logic (5v) gives maximum speed logically though it may vary based on the battery supply.

The Pico woks at a logic of 3.3v, ...so even at 100% cycle the enable pin gets 3.3v, documents mention that the l298n module uses ttl logic levels but I don't quite know if all this effects the range of speeds that could be achieved ...

I may be wrong in the way I'm understanding things tho, but actually measuring the rpms should help. Regardless I was wondering if someone had experience with this before.

8

I don't really have access to a scope rn :sweat_smile:

9

I think I understand where I went wrong.

The pwm sent to the enable pin just turn on and off the supply voltage to the motors really fast and hence pwm the motor supply voltage to control motor speeds..meaning at the enable pin..as long as logic high and low are distinguishable it shouldn't matter whether the logic level is 3.3v or 5v.

I think this was what runaway pancake was trying to explain earlier on this thread :sweat_smile:

I was trying to do something else entirely but this question popped in my head and confused me, I over complicated a simple thing.

Thank you for all the replies tho, I appreciate them

10

No it does not. That is where your thinking is wrong.

11

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