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How to stop electrical whining noise?

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John Doe
Guest

Wed Dec 26, 2018 5:45 am   



https://youtu.be/FSwZQtqWyHw

Can that whining noise be easily eliminated?

I am assuming its origin is easy for some to guess.
It uses brushless motors controlled by an "electronic speed control"
(ESC). There is a large cap across each ESC supply plus and minus. I
tried adding a 1000 F low ESR capacitor on the battery input but that
didn't help.

Thanks.


Guest

Wed Dec 26, 2018 6:45 am   



The blades.

Also, emitting a shitload of sound is inefficient. Anything that makes unwanted motion or energy is wasting.

Yeah they probably want me to teach greengineering but fuck all that.

What you hear is the fans' blades interacting with the air, but which then the sound is transmitted to you. And others, who might bitch.

Bottom line, the sound is not coming from the motors.

Sjouke Burry
Guest

Wed Dec 26, 2018 6:45 am   



On 26-12-2018 5:02, John Doe wrote:
Quote:
https://youtu.be/FSwZQtqWyHw

Can that whining noise be easily eliminated?

I am assuming its origin is easy for some to guess.
It uses brushless motors controlled by an "electronic speed control"
(ESC). There is a large cap across each ESC supply plus and minus. I
tried adding a 1000 F low ESR capacitor on the battery input but that
didn't help.

Thanks.

maybe magnetically induced noise? Bigger caps cannot cure that.


Jasen Betts
Guest

Wed Dec 26, 2018 6:45 am   



On 2018-12-26, John Doe <always.look_at_message.header> wrote:
Quote:
https://youtu.be/FSwZQtqWyHw

Can that whining noise be easily eliminated?

I am assuming its origin is easy for some to guess.
It uses brushless motors controlled by an "electronic speed control"
(ESC). There is a large cap across each ESC supply plus and minus. I
tried adding a 1000 µF low ESR capacitor on the battery input but that
didn't help.


my guess it that it's coming from the motors.


--
When I tried casting out nines I made a hash of it.

bitrex
Guest

Wed Dec 26, 2018 7:45 am   



On 12/26/2018 12:13 AM, Jasen Betts wrote:
Quote:
On 2018-12-26, John Doe <always.look_at_message.header> wrote:
https://youtu.be/FSwZQtqWyHw

Can that whining noise be easily eliminated?

I am assuming its origin is easy for some to guess.
It uses brushless motors controlled by an "electronic speed control"
(ESC). There is a large cap across each ESC supply plus and minus. I
tried adding a 1000 µF low ESR capacitor on the battery input but that
didn't help.

my guess it that it's coming from the motors.



Does the noise stop when you turn it off? Right. well. There's yer problem

Jeff Liebermann
Guest

Wed Dec 26, 2018 7:45 am   



On Wed, 26 Dec 2018 04:02:07 -0000 (UTC), John Doe
<always.look_at_message.header> wrote:

>https://youtu.be/FSwZQtqWyHw

The video is from 2005.

>Can that whining noise be easily eliminated?

Maybe. Propeller tip vortexes and cavitation are making the noise.
The only way to reduce that is to reduce RPM's, which means you'll
need larger diameter props, or by clever prop design. Some
manufacturers offer low-noise props. I've never tried any, so I have
no clue if they actually work.
<https://airbuzz.one/why-i-dont-use-the-low-noise-propellers-anymore/>

I couldn't find any for Walkera, just DJI:
<https://www.amazon.com/Anbee-Low-Noise-Propeller-Quick-Release-Platinum/dp/B07795ZT1P>

Various low-noise propeller tests:
<https://www.youtube.com/results?search_query=low+noise+propeller>

>I am assuming its origin is easy for some to guess.

I never guess when I can also test.
1. Take a vinyl hose and cram one end in your ear. Use the other end
to determine the source of the noise. I think you'll find that it
makes the most noise near the tips of the props.
2. Remove the props from all the motors. Run the quadcopter without
the props. What's left is the contribution made by the brushless
motors, which I think you'll find isn't very much.

Quote:
It uses brushless motors controlled by an "electronic speed control"
(ESC). There is a large cap across each ESC supply plus and minus. I
tried adding a 1000 F low ESR capacitor on the battery input but that
didn't help.


Filtering the DC power inputs isn't going to do anything useful.

--
Jeff Liebermann jeffl_at_cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

bitrex
Guest

Wed Dec 26, 2018 7:45 am   



On 12/26/2018 12:58 AM, Jeff Liebermann wrote:
Quote:
On Wed, 26 Dec 2018 04:02:07 -0000 (UTC), John Doe
always.look_at_message.header> wrote:

https://youtu.be/FSwZQtqWyHw

The video is from 2005.

Can that whining noise be easily eliminated?

Maybe. Propeller tip vortexes and cavitation are making the noise.
The only way to reduce that is to reduce RPM's, which means you'll
need larger diameter props, or by clever prop design. Some
manufacturers offer low-noise props. I've never tried any, so I have
no clue if they actually work.
https://airbuzz.one/why-i-dont-use-the-low-noise-propellers-anymore/

I couldn't find any for Walkera, just DJI:
https://www.amazon.com/Anbee-Low-Noise-Propeller-Quick-Release-Platinum/dp/B07795ZT1P

Various low-noise propeller tests:
https://www.youtube.com/results?search_query=low+noise+propeller

I am assuming its origin is easy for some to guess.

I never guess when I can also test.
1. Take a vinyl hose and cram one end in your ear. Use the other end
to determine the source of the noise. I think you'll find that it
makes the most noise near the tips of the props.
2. Remove the props from all the motors. Run the quadcopter without
the props. What's left is the contribution made by the brushless
motors, which I think you'll find isn't very much.

It uses brushless motors controlled by an "electronic speed control"
(ESC). There is a large cap across each ESC supply plus and minus. I
tried adding a 1000 µF low ESR capacitor on the battery input but that
didn't help.

Filtering the DC power inputs isn't going to do anything useful.


Right the noise is mechanical, not electrical. Parts that are rotating
and making sound. If it were a jet engine OP would be looking for some
kind of "hush kit"

Klaus Kragelund
Guest

Wed Dec 26, 2018 8:45 am   



It sounds to me like it is switching noise from the motor drive, which causes movement of the motor windings

It sounds to be a steady noise frequency which it won’t be if it is related to the blades

No way to change it, except to change the motor control SW or filter the output to the motor to reduce the switching current ripple

Cheers

Klaus

John Doe
Guest

Wed Dec 26, 2018 8:45 am   



Jeff Liebermann <jeffl_at_cruzio.com> wrote:

Quote:
John Doe <always.look_at_message.header> wrote:

https://youtu.be/FSwZQtqWyHw

The video is from 2005.


The video is from 2015. I thought about posting a disclaimer after
clicking Send, but it's not necessary. The video is a concise and
accurate example of the same noise from the same model drone.

I already have some third-party props to try. I just need to grind
the nuts for them.















Quote:
Can that whining noise be easily eliminated?

Maybe. Propeller tip vortexes and cavitation are making the noise.
The only way to reduce that is to reduce RPM's, which means you'll
need larger diameter props, or by clever prop design. Some
manufacturers offer low-noise props. I've never tried any, so I have
no clue if they actually work.
https://airbuzz.one/why-i-dont-use-the-low-noise-propellers-anymore/

I couldn't find any for Walkera, just DJI:
https://www.amazon.com/Anbee-Low-Noise-Propeller-Quick-Release-Platinum/dp/B07795ZT1P

Various low-noise propeller tests:
https://www.youtube.com/results?search_query=low+noise+propeller

I am assuming its origin is easy for some to guess.

I never guess when I can also test.
1. Take a vinyl hose and cram one end in your ear. Use the other end
to determine the source of the noise. I think you'll find that it
makes the most noise near the tips of the props.
2. Remove the props from all the motors. Run the quadcopter without
the props. What's left is the contribution made by the brushless
motors, which I think you'll find isn't very much.

It uses brushless motors controlled by an "electronic speed control"
(ESC). There is a large cap across each ESC supply plus and minus. I
tried adding a 1000 F low ESR capacitor on the battery input but that
didn't help.

Filtering the DC power inputs isn't going to do anything useful.


bitrex
Guest

Wed Dec 26, 2018 9:45 am   



On 12/26/2018 02:30 AM, Klaus Kragelund wrote:
Quote:
It sounds to me like it is switching noise from the motor drive, which causes movement of the motor windings

It sounds to be a steady noise frequency which it won’t be if it is related to the blades

No way to change it, except to change the motor control SW or filter the output to the motor to reduce the switching current ripple

Cheers

Klaus


if it's electrically excited/resonant acoustic noise caused by a
specific PWM harmonic in the audible range (the whine seems to be
consistent in frequency across the motor power output range) what about
a parallel-series LC band-reject in the PWM drive output to the motors?
The armature can't resonate at that frequency if it can't get any power
from the controller at that frequency

John Doe
Guest

Wed Dec 26, 2018 9:45 am   



bitrex <user_at_example.net> wrote:

Quote:
Klaus Kragelund wrote:

It sounds to me like it is switching noise from the motor drive,
which causes movement of the motor windings

It sounds to be a steady noise frequency which it won’t be if
it is related to the blades

No way to change it, except to change the motor control SW or
filter the output to the motor to reduce the switching current
ripple

I hear it now. Had to put on headphones, on laptop speakers I only
hear the lower pitched blade noise


I was just coming back to post about that possibility. The frequency
is at least 8 kHz. A bad sound system or failing ears might not even
know what sound we're talking about.

Klaus Kragelund
Guest

Wed Dec 26, 2018 9:45 am   



I hear a steady switching noise, in the neighborhood of 10kHz

bitrex
Guest

Wed Dec 26, 2018 9:45 am   



On 12/26/2018 02:30 AM, Klaus Kragelund wrote:
Quote:
It sounds to me like it is switching noise from the motor drive, which causes movement of the motor windings

It sounds to be a steady noise frequency which it won’t be if it is related to the blades

No way to change it, except to change the motor control SW or filter the output to the motor to reduce the switching current ripple

Cheers

Klaus


I hear it now. Had to put on headphones, on laptop speakers I only hear
the lower pitched blade noise


Guest

Wed Dec 26, 2018 10:45 am   



bitrex
Quote:
On 12/26/2018 02:30 AM, Klaus Kragelund wrote:
It sounds to me like it is switching noise from the motor drive, which causes movement of the motor windings

It sounds to be a steady noise frequency which it won’t be if it is related to the blades

No way to change it, except to change the motor control SW or filter the output to the motor to reduce the switching current
ripple

Cheers

Klaus


if it's electrically excited/resonant acoustic noise caused by a
specific PWM harmonic in the audible range (the whine seems to be
consistent in frequency across the motor power output range) what about
a parallel-series LC band-reject in the PWM drive output to the motors?
The armature can't resonate at that frequency if it can't get any power
from the controller at that frequency


I is most likely
https://en.wikipedia.org/wiki/Siren_(mythology)
seducing pilots to put their ear next to the propellors
and then have those chopped off.

A classic.

Klaus Kragelund
Guest

Wed Dec 26, 2018 11:45 am   



Yes, you can filter it with LC filter

But as I hear it, the high frequency noise is same level as the blade noise, so why bother?

The frequency is low to reduce power switching losses, if you add LC, losses will rise a lot

Cheers

Klaus

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