Audible noise in dc motors - Page 1
Forum section: electronics / beginners

author: Vindhyachal.takniki
author_rank: Frequent Contributor
timestamp: March 21, 2016, 08:21:19 am
content: 1. I have a simple application in which three dc motors are controlled by MCU with a mosfet.Motor is 12V dc motor & load is small robo tyre as in attached video. This is not much load & moreover tyre dont move on road it is hanging upwards so no friction of road or anything.2. Problem is as you can hear motor produces too much audible noise , is there any way to reduce it or any silent 12Vdc motor. SO that when motor rotates no noise or little noise is produced. I need 150rpm or 200rpm motor.https://www.youtube.com/watch?v=XhkE5fJk74A&feature=youtu.be

author: Simon
author_rank: Unknown
timestamp: March 21, 2016, 08:26:49 am
content: Are you controlling it with PWM ?

author: Vindhyachal.takniki
author_rank: Frequent Contributor
timestamp: March 21, 2016, 08:41:37 am
content: Yes. Four type of PWM signal for each motor: 100%, 75%,50%,25%

author: Kilrah
author_rank: Unknown
timestamp: March 21, 2016, 08:41:53 am
content: 1sec is a bit short for a video...Looks like geared motors, the noise likely comes from the gears.

author: Simon
author_rank: Unknown
timestamp: March 21, 2016, 08:43:15 am
content: Quote from: Vindhyachal.takniki on March 21, 2016, 08:41:37 amWhat frequency ? you need to use a frequency over 10KHz so that you do not hear the motor vibrating.

author: LA7SJA
author_rank: Regular Contributor
timestamp: March 21, 2016, 08:47:17 am
content: This sounds like noisy gearboxes more than motor noise. Try reading this document on noise in this document "Vibrations and Noises in Small Electric Motors"http://www.micromo.com/media/wysiwyg/Technical-library/Vibrations-Dr-Bertolini.pdfJohan-Fredrik

author: Vindhyachal.takniki
author_rank: Frequent Contributor
timestamp: March 21, 2016, 08:48:31 am
content: Yes it is geared motor.At 25%: 125us on, 500us periodAt50%: 250us on, 500us periodand so on

author: Simon
author_rank: Unknown
timestamp: March 21, 2016, 08:50:06 am
content: Quote from: Vindhyachal.takniki on March 21, 2016, 08:48:31 amSo 2KHz, you would hear that as a high pitched whine but from what others are saying (I can't play your video right now) your gears might be making more noise.

author: LA7SJA
author_rank: Regular Contributor
timestamp: March 21, 2016, 09:06:04 am
content: I did not find much of the 2KHz in a quick scope FFT but the sample was only 1 sec and I didn't bother to make a loop recording. So the culprit is probably the sloppy gearboxes.Johan-Fredrik

author: Vindhyachal.takniki
author_rank: Frequent Contributor
timestamp: March 21, 2016, 09:35:47 am
content: Are dc motor available for 12Vdc,150rpm, which dont produce this geared noises & can bear a tyre load as in video?

author: XOIIO
author_rank: Super Contributor
timestamp: March 21, 2016, 09:58:03 am
content: Quote from: Vindhyachal.takniki on March 21, 2016, 09:35:47 amGenerally motors don't come with gearboxes, they are separate parts.

author: Aleksandar B.
author_rank: Contributor
timestamp: March 21, 2016, 11:40:47 am
content: Quote from: Vindhyachal.takniki on March 21, 2016, 09:35:47 amI think it is impossible to find an off-the-shelf motor with such low RPM. Motors, in general, have very high RPM and are very inefficient if used at lower voltages to lower the RPM.

author: protec
author_rank: Newbie
timestamp: March 21, 2016, 12:06:48 pm
content: Seems as the weight on those shafts might be a bit excessive for the motor capacitance. Example, putting a 300lbs man on a 150lbs Guy's back. You think he is going to groan a little? Try supporting those wheels somehow. So that the shaft runs freely. Just a balance point will cause longer life to the motors bc I think you are wearing those motors out.Sent from my iPhone using Tapatalk

author: LA7SJA
author_rank: Regular Contributor
timestamp: March 21, 2016, 02:49:12 pm
content: Maybe you should start by reading thishttp://www.societyofrobots.com/mechanics_gears.shtmlthis should explain some of the problems you are facing and send you in the right direction. The way you try to build this is not going to work am I afraid. You should try and see some of the technics used in RC car or "fighting" robots, they have developed a few smart ways to put power on the ground (and it's not so noisy as your contraption).Johan-Fredrik

author: albert22
author_rank: Regular Contributor
timestamp: March 21, 2016, 06:42:17 pm
content: It seems that the noise comes from the gears. But you can discard the PWM by testing the motors with a variable DC power supply.

author: Audioguru
author_rank: Super Contributor
timestamp: March 21, 2016, 11:57:04 pm
content: Can you use quiet pulleys instead of noisy gears?

author: Back2Volts
author_rank: Unknown
timestamp: March 22, 2016, 02:12:31 pm
content: Gear box, inadequate support for the wheel shafts, acoustic amplification by plastic wheels (speaker like)

author: G7PSK
author_rank: Super Contributor
timestamp: March 23, 2016, 08:27:54 am
content: I only hear a rattle, that would most likely be due to the wheel wobble causing the shaft and gears to rattle. Balance the wheels and get them mounted square on the shaft, they are running out of true by a fair amount.

author: Vindhyachal.takniki
author_rank: Frequent Contributor
timestamp: March 23, 2016, 06:57:58 pm
content: I will try with stepper motor to see result rather than dc motor. i had tried two other d motor but same results