Go Down

Topic: DC MOTOR NOISE (Read 6770 times) previous topic - next topic

humapoc

dear friends,


please help and advise

i have this motor. http://tm-k.co.kr/bbs/board.php?bo_table=dc_motor_4&wr_id=45&page=2

when i connect motors to arduino mega through motor shield and start there is much noise from arduino and motor


please advise what capacitor should i use with this motor.



MarkT

A small ceramic cap should go directly across the motor terminals, maybe 100nF.  This will
reduce noise from the sparking of the commutator being transmitted up the wires.

Check if the noise is PWM, and consider changing the PWM frequency.

Add lots of decoupling to the motor supply itself, 1000uF or so perhaps, which will be electrolytic
(which is polarized, make sure its the right way round and has adequate voltage rating).  That
will reduce noise on the power supply wiring.
[ I DO NOT respond to personal messages, I WILL delete them unread, use the forum please ]

jremington

Pololu has a short tutorial on reducing motor noise.

Grumpy_Mike

Are we talking about electrical noise or audio noise here?

humapoc


bodmer

It would be useful to describe the symptoms of the problem you are trying to fix...

I doubt a capacitor will help. The potential problem areas I see are:

1. You have selected a motor with a high stall current (10A for 12V motor)
2. Typical motor shields only handle up to 2A (which one do you have?)
3. The low PWM frequency and low motor inductance (implied by it's current rating) will lead to high peak currents
4. The high peak currents will need a low impedance power source to feed the motor shield otherwise the rail will collapse and upset any other electronics fed from that supply


humapoc

Thanks for your feedback. I use motor shield 2 A. Each Motor < 1600 mA. Together 3000 mA. May be i should use 2 motor shields?

bodmer

It would be useful to describe the symptoms of the problem you are trying to fix... i.e. what is not working as expected?

humapoc

Everything works fine. But there is noise coming from arduino and motors while moving.

bodmer

#9
Jul 10, 2016, 04:23 pm Last Edit: Jul 10, 2016, 04:23 pm by bodmer
Is the noise causing a problem?  If so what is the problem?

For example, it looks like you have built a line follower. Is the noise affecting it's behavior?

Or is the noise actually just a "whistle" or "whine" you can hear? (from the motor PWM drive frequency)

humapoc

YES THE NOISE IS JUST A STRONG WHISLE.

THANKS FOR YOUR HELP IN ADVANCE.

bodmer

That is caused by the PWM frequency that drives the motor.

Options:
1. Just use on/off "bang bang" control so motor is fully switched off or fully on, probably not an option unless you have a high gear ratio
2. Increase the PWM frequency by code hacks
3. Cover the robot with noise absorbent foam and soft mount the motors on rubber bushes :)
4. Change the motors to higher quality units (generally much higher cost, but tend to generate less audible PWM noise)

If everything else works then you have done a good job!

outsider

#12
Jul 10, 2016, 05:11 pm Last Edit: Jul 10, 2016, 05:23 pm by outsider
Have you tried different PWM pins? PWM frequency on pins 3, 9, 10 & 11 is about 470 Hz, on pins 5 & 6 about 940 Hz. Might give a less annoying whistle.
EDIT: Just noticed you're using a Mega, never mind.  :-[

bodmer

Pins 3 and 11 are used by the motor shield for PWM. These operate at ~490Hz

Add these lines to setup() when using a Mega and the PWM will run at 3.9kHz

Code: [Select]

TCCR1B = (TCCR1B & 0xF8) | 0x02; // Pin 11 (and 12)
TCCR3B = (TCCR3B & 0xF8) | 0x02; // Pin 3 (and 2, 5)


This may be less annoying  :)

Grumpy_Mike

electrical noise
Why did you say that?
When you went on to shout:-
YES THE NOISE IS JUST A STRONG WHISLE.
This is quite clearly acoustic noise. This is why I asked the question and you did not tell the truth. Do you lie about other things too?

Go Up