Electric noise.

[svol]

I got an irritating problem with my 2 Enermax 120mm adjustable fan which are used to cool my radiator. They seem to create electronic disturbance/noise which I can hear on my speakers when it is connected with my PSU.

I think the fans use PWM (Pulse-Width Modulating) to change speed and it seems the pulses are transmitted through the PSU black (ground) wire. I already tried whinding both the positive 12V wire as the ground wire around feriet rings to see if that stops the noice with no success.

For now I'm running the fans with a small universel adapter I use for my MP3/CD-man and that also can put out 12V... but if any of you can advice a way to stop the electric magnetic interference (EMI) I will be interested to hear your solution.

Thanks in advance!

I love my Delta 60HP 7000 RPM fan that puts out more dB then CFM

 

[lhgpoobaa]

hmmm.
IIRC dan at <A HREF="http://www.dansdata.com/danletters056.htm" target="_new">http://www.dansdata.com/danletters056.htm</A> recently answered a letter asking something similar.

Maybe it helps.

P.S. Have you tried disabling the signalling wire? and does the sound change pitch as you vary the fan speed?

I cant say i ever got any interferance with my 80mm enermax variable.

<b>Regards,
Mr no integrity coward.</b>

 

[Woodman]

This probably isn't it, but did you by any chance wrap, or bundle your analogue audio wire (from your CD drive to sound card) together with other power/IDE wires?

-----
I'm going to get you.

 

[svol]

One goes together with some temp sensor and the other hangs free in my system... they always did this. The problem started with my new fans and it dissapears when I disconnect them.

I love my Delta 60HP 7000 RPM fan that puts out more dB then CFM

 

[svol]

Hmmm... it seems to be traffeling through the power wires so I dunno if that fixes it. But I will try cutting the RPM wires (which I don't use actually).

I think the fact that my PC isn't grounded (I don't have a ground wire in my room) may increase vulnerabilty for EMI, but even when I shutdown my PC and let the fans run at the external adapter with the speakers on I can hear the noice... so I think it traffels through my power cables.

Man I need an electronics expert to figure this out... :frown:

I love my Delta 60HP 7000 RPM fan that puts out more dB then CFM

 

[phsstpok]

Try muting everything in your sound mixer.

This should tell you if the sound is being fed through one of your audio inputs and being amplified OR it will tell you that noise is somehow being carried directly to your speakers, as in through a ground loop.

<b>56K, slow and steady does not win the race on internet!</b><P ID="edit"><FONT SIZE=-1><EM>Edited by phsstpok on 08/04/03 03:05 PM.</EM></FONT></P>

 

[TheMASK]

Man I need an electronics expert to figure this out...

am ur man.


<font color=red>I only write to get more posts...</font color=red>

 

[Guest]

Please clear this up for me: You say the problem goes away when you use an isolated supply (your little MP3 player power supply)?

If that is true you have already done half the troubleshooting work right there. Is there any possibility that these new fans are pushing your power supply loading over it's rated?

One thing you could try if you really believe it is a conducted problem is: Try a 1000uF or so low ESR aluminum electrolytic cap right across the power leads at the fan, probably 25V working voltage or so should do. What this does is create a local tank for power the fan can use so it isn't (as) affected by the IR drops in it's own power cable. An RC filter if you will, where the R is the inherent resistance in the cable, and the C is the 1000uF.

 

[svol]

It goes directly to the speakers... even with the PC off and the secondary adapter on I can still hear it (although it is much more quiet then when the fans are connected with the PSU). So I guess it traffels through my 230V power wires... or it creates a very big EMI field that interveres with the wires 50 cm away.

I love my Delta 60HP 7000 RPM fan that puts out more dB then CFM

 

[svol]

Well not really away... but the noise gets less.

As for the PSU reaching its max... that is not it. The fans are only 3W in total and if I connect/disconnect my secondary 2 HDs the problems still exists.

I will see if I can find a 1000uF/25V capacitator somewhere around... maybe from an old PSU or otherwise I will try a local store.

I love my Delta 60HP 7000 RPM fan that puts out more dB then CFM

 

[Guest]

"Well not really away... but the noise gets less."

What is left is probably radiated. If so, it leaves a much trickier situation to analyze. You should be able to get to the same noise level as when you are using the MP3 supply with the cap trick I mentioned.

As for the radiated emission problem if it is still too unbearable....

Low quality audio circuits are notorious for high impedance amplifier inputs which are more susceptible to radiated emissions. If there is any question about your speakers quality (mostly applies to analog input speakers, but not necessarily, any amplified ckt really), you might try to test with a relatively higher quality pair.

Otherwise you are down to such witchcraftery as going all digital to shielded speakers, or trying some sheilding on your analog signal lines. Or better yet, shielding at the source of the emissions, the fans.

 

[svol]

I got a Creative Cambridge Soundworks 4.1 Surround set... working great for more then 3 year.

I love my Delta 60HP 7000 RPM fan that puts out more dB then CFM

 

[svol]

I found a 1000uF 35V capacitator... that would do right?

I love my Delta 60HP 7000 RPM fan that puts out more dB then CFM

 

[Guest]

Even better. Just make sure to hook the + and - sides up right, as almost all electrolytics are polarized. Normally the minus will be marked on the cap case.

Remember to hook the leads as electrically close to the fan motor as possible. Obviously for testing, any fan which you haven't sismilarly modified should be left off for the test.

I would be interested in hearing about the results....

 

[Guest]

"I got a Creative Cambridge Soundworks 4.1 Surround set... working great for more then 3 year."

A great set I'm sure, but it sounds as if these fans are creating an exceptionally harsh environment. Another trick I remembered....be sure to test with the case covers on as the grounded PC cases are doing significant shielding. As usual the best shielding will be had by the windowless steel grounded cases.

Since you mentioned that there is no earth in your wiring, you may want to try and experiment with adding your own earth connection directly to the PC chassis. This will help shielding with the benefit that your system will be safer as well. Maybe a steel, or copper water pipe would make a good choice for places to earth to.

 

[svol]

Well the capacitator only increased the noise. I'm now going to try to should all cables and run the wires through several feriet rings.

I love my Delta 60HP 7000 RPM fan that puts out more dB then CFM

 

[Guest]

Before you give up on the cap you should try it in one other configuration.

This time put it as close to the power source as possible, Ie at the other end of the cable or inside the power supply if possible.

Maybe I was just being a dumbass about placement. It would be a shame to not run the one other simple test, and find out that could have helped.

Any way, I don't really have much after that. Good luck.