Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 6th March 2011, 10:15 AM   #1
diyAudio Member
 
Join Date: Oct 2009
Location: Tasmania
Default Buzz noise from DC brushless fan in TDA2822m

Hi all, I'm trying to implement a tiny cooling fan in my TDA2822m project (yes, it's only 1W), but I just want to make sure it doesn't overheat if driven hard, plus it will look more geeky...

The problem is that it creates a buzz (square wave or spike) directly related to rpm. Only in the right channel, and gets a little louder as the fan gets closer to the chip. Still there to be annoying within the circuit box.

Would resistors either side of the fan reduce the noise (it has to have resistors any way to slow it down)? I can't try anything until next weekend, so I thought I may as well ask here.

What about an RC in parallel? Though getting that exact frequency will be difficult enough.

Any other possible solutions?

Thank you in advance for any help,

E.E
  Reply With Quote
Old 7th March 2011, 09:57 AM   #2
diyAudio Member
 
Join Date: May 2008
Does the fan already have a power supply of its own?
RC in parallel is more promising than resistors in series.
__________________
If you've always done it like that, then it's probably wrong. (Henry Ford)
  Reply With Quote
Old 9th March 2011, 09:11 AM   #3
sasmit is offline sasmit  India
diyAudio Member
 
Join Date: May 2006
Send a message via Yahoo to sasmit
Quote:
Originally Posted by enigmaticEntity. View Post
Hi all, I'm trying to implement a tiny cooling fan in my TDA2822m project (yes, it's only 1W), but I just want to make sure it doesn't overheat if driven hard, plus it will look more geeky...

The problem is that it creates a buzz (square wave or spike) directly related to rpm. Only in the right channel, and gets a little louder as the fan gets closer to the chip. Still there to be annoying within the circuit box.

Would resistors either side of the fan reduce the noise (it has to have resistors any way to slow it down)? I can't try anything until next weekend, so I thought I may as well ask here.

What about an RC in parallel? Though getting that exact frequency will be difficult enough.

Any other possible solutions?

Thank you in advance for any help,

E.E
Is the fans ground connected to your signal ground ?

The fan should ideally be connected to power ground i.e. assuming you're using separate grounds.

There are two ways the fan creates noise one will be through the power supply, the other is through EMI generated from the switching components inside the fan , this is most probably your problem since you're saying it increases if you take the fan near the amp.
For this I think you need to isolate your circuitry using a ground plane or a copper shield etc.
  Reply With Quote
Old 9th March 2011, 06:27 PM   #4
diyAudio Member
 
Join Date: May 2008
Switching components inside a fan?
__________________
If you've always done it like that, then it's probably wrong. (Henry Ford)
  Reply With Quote
Old 10th March 2011, 03:17 AM   #5
sasmit is offline sasmit  India
diyAudio Member
 
Join Date: May 2006
Send a message via Yahoo to sasmit
Quote:
Originally Posted by pacificblue View Post
Switching components inside a fan?
yes ! The brushless dc motor has a hall effect sensor and a pwm + switching components inside. When you look at it, it doesn't seem like much until I read an elektor article about brushless fans

Last edited by sasmit; 10th March 2011 at 03:21 AM.
  Reply With Quote
Old 10th March 2011, 04:07 AM   #6
diyAudio Member
 
Join Date: Nov 2009
Location: Los Angeles
Quote:
Originally Posted by sasmit View Post
Is the fans ground connected to your signal ground ?

The fan should ideally be connected to power ground i.e. assuming you're using separate grounds.

There are two ways the fan creates noise one will be through the power supply, the other is through EMI generated from the switching components inside the fan , this is most probably your problem since you're saying it increases if you take the fan near the amp.
For this I think you need to isolate your circuitry using a ground plane or a copper shield etc.
You're right about the grounds. An RC filter on the fan like 2.7 ohms in series and 220 uF in parallel would help also. He shouldn't need ground planes, just a proper power return so it doesn't get into the signal path. If the input loading of he amp is low (25K, or my preference <10K) EMI should not be the issue. It's the ground 'bouncing' from the power surges of the fan at commutation time.

G
  Reply With Quote
Old 10th March 2011, 05:45 PM   #7
diyAudio Member
 
Join Date: May 2008
Quote:
Originally Posted by sasmit View Post
yes ! The brushless dc motor has a hall effect sensor and a pwm + switching components inside. When you look at it, it doesn't seem like much until I read an elektor article about brushless fans
The hall sensor is used as feedback signal for PCs so that you get an alarm when the fan is stuck. I don't think it is connected in this application.
The PWM current limiter that may or may not be built into the fan is usually only active during start-up to limit the inrush current. That should also not be an issue.
Brushless motors do however produce significant ripple of their own, that is why they should have a separate power supply.
__________________
If you've always done it like that, then it's probably wrong. (Henry Ford)
  Reply With Quote
Old 11th March 2011, 07:10 PM   #8
johnr66 is offline johnr66  United States
diyAudio Member
 
Join Date: Mar 2009
I'm trying to understand the need for a fan in the first place. Are you overdriving the chip? epoxy a U shaped heat sink to the top would be a better passive solution. A fan probably won't do much for the tiny surface area without an additional sink.
  Reply With Quote
Old 11th March 2011, 08:31 PM   #9
diyAudio Member
 
Join Date: Apr 2003
Location: Portland,Oregon
Blog Entries: 4
Send a message via AIM to DigitalJunkie
I usually use a RC on fans to filter out the noise. Depending on how slow you want the fan to run 10-100ohms,followed up with a 100-220uf cap usually does it for me.
  Reply With Quote
Old 15th March 2011, 11:18 AM   #10
diyAudio Member
 
Join Date: Oct 2009
Location: Tasmania
Sorry I haven't replied for a while The noise is from EMI I think, as I attached the fan via a longer line and the noise was gone when about 15cm away. It also disappears when the fan is orientated so air is blowing at a tangent to the amp (Not very useful!)

The enclosure as it stands is already overcrowded, and the fan can only go above the amp at a distance of about 3-4cm. I'm guessing I need some sort of EMI RF shield that can let air flow through it easily?

There is a heatsink on the chip, scavanged from a CRT circuit board, about 3*1*1 cm dimensions, black Alu. It is tied on with string, glued with superglue and has thermal compund in between.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Brushless DC fan - power question Stuey Everything Else 4 13th October 2009 04:51 AM
Assistance in diagnosing Hum/Buzz/Noise xenithon Digital Line Level 37 24th January 2009 06:39 PM
Melos triode and computer as source: BUZZ BUZZ BUZZ zigo3 Tubes / Valves 4 28th November 2007 02:11 AM
buzz noise from loud speakers vibeline Multi-Way 9 7th January 2007 06:19 PM
Buzz Noise on outputs with inputs attached akunec Chip Amps 3 7th March 2005 12:31 AM


New To Site? Need Help?

All times are GMT. The time now is 11:49 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2