[SOLVED] 5V PoE generates annoying sound (youtube)

Hello,

I just soldered a brand new PoE module onto my Yun. (bought on arduino.cc). When i connect my Yun onto my PoE+ switch a strange sound is generated from the PoE module. The Yun is getting power over the ethernet cable. But that noise can't be normal?

I've made a short video that captured the sound: https://www.youtube.com/watch?v=crGa9u51yBo

It's annoying... Why is it doing that? An other PoE injector did not solve this. So it must be something with the PoE module.

All pins are soldered correctly. And the ethernet shield is not touching any pins on the PoE board.

My other Arduino board (EtherDue) with PoE does not make this noise...

Can i do something to resolve / reduce this sound issue?

Greetz, Vinzz

There's a lot of static in the recording, which makes it hard to hear, but there seems to be a very high frequency whistle that stops as soon as you unplug the cable. I assume this is what you're hearing?

To me, that sounds like the switching power supply. Usually, the frequency is high enough to be inaudible. When it's that that pronounced, I find that it's often an overload condition where the supply is straining to provide enough power. What is the output current rating of the module?

In rare cases, I've seen where a bad transformer has loose windings that vibrate at the switching frequency, but most of the time it seems to be an overload.

indeed, it's that high frequency whistle.

forgot to post a link to the PoE module in my previous post: http://store.arduino.cc/product/X000010 -> Ag9605-S 5V 9 Watts

This module should meet the requirements for the yun (as the explanation also states.)

Yes, 9 Watts is 1.8 Amps @ 5V, so that should be plenty of capacity.

Hopefully, someone using that module will be along to give their experiences.

I have a very similar module using an Ag9700 and have the same sound.

Also i have noticed that when powered by POE i can not get the bridge library to initialize.

It is a real pity as i was thinking that with POE this would be a great small device that i could use all over the place but with the noise and not been able to get the system up and working is a real downer.

ShapeShifter: ... In rare cases, I've seen where a bad transformer has loose windings that vibrate at the switching frequency, but most of the time it seems to be an overload.

It might be the case.

http://www.reddit.com/r/arduino/comments/2taq1d/arduino_ethernet_with_poe_module_high_pitch_sound/

we bought 20 Arduinos Ethernet with PoE modules at work and maybe half of them are making continuous high pitch sounds when on.

Chuck a bit of goop on it, let it dry, problem solved.

Davey_Rance:
I have a very similar module using an Ag9700 and have the same sound.

Also i have noticed that when powered by POE i can not get the bridge library to initialize.

It is a real pity as i was thinking that with POE this would be a great small device that i could use all over the place but with the noise and not been able to get the system up and working is a real downer.

Yun current load 200~300 mA

Ag9600

Page 17

Minimum Load 100mA Ag9605

Ag9700

Page 22.

Minimum Load 200mA Ag9705

Ag9705-s is not direct replacement for Ag9605-s.

Davey_Rance: Also i have noticed that when powered by POE i can not get the bridge library to initialize.

The bridge and all the rest of the arduino is working fine. (even with 16x2 lcd and a rotary encoder). But that high frequency noise is very annoying. I can still hear it when i'm 10 meters away.

sonnyyu: Chuck a bit of goop on it, let it dry, problem solved.

What do they actually mean? Do i have to glue something?

VinzzB: What do they actually mean? Do i have to glue something?

Many times, the transformer will have an exposed core and exposed windings. Squirting some glue or silicone RTV into it can stop the vibrations. Bu the transformer in the link you posted looks to have a cube shell covering it, so the glue option may not do much for you.

Can you press you finger on various locations of the board and see if the noise stops? If so, you've found the component that is vibrating, and some goop to stabilize might help. But if it's inside the transformer, and the transformer is enclosed, you might be out of luck.

The OEM of POE module:

http://www.silvertel.com

Tel: +44 1633 817199 Fax: +44 1633 815415 email: sales@silvertel.com

drop a line or fax issue to them, some time you are lucky enough to receive new revision module on mail for free. Never hurt.

ShapeShifter: Can you press you finger on various locations of the board and see if the noise stops?

I already tried various press actions. even with some pincers (on transformer). but nothing seems to work.

I'm going to mail silvertel, hopefully i get a response from them.

VinzzB: I'm going to mail silvertel

Good call. :sunglasses:

Hi, Im An engineer from Silvertel

This whistle is the PoE modules DC-DC converter running unstable caused by lack of output capacitor.

We have already informed Arduino that they have not followed our datasheet; by not fitting an electrolytic capacitor across the PoE modules output pins.

In the Ag9600 datasheet, we specify using a 470uF electrolytic capacitor directly across the output pins. Here is a link to our datasheet, see Section 5.7 - http://www.silvertel.com/images/datasheets/Ag9600-datasheet-isolated-Power-over-Ethernet-PoE-module-solution.pdf

We have conducted tests for other Yun user and have worked out that you should be able to get away with fitting a 100uF 6.3V tantalum across the Ag9605-2BR output. Because Arduino haven’t made any provision on their Yun board for fitting an output capacitor, it has to be soldered directly across the pins (negative to pin 7 and positive to pin 8 ).

Attached is a photo showing the position of the capacitor on the bottom of the Yun board. https://dl.dropboxusercontent.com/u/23654687/Arduino%20Yun%20Tantalum%20Mod.jpg

We have informed Arduino of this mistake, in a hope that they will correct this mistake on the next revision of their Yun board.

Regards

Apps Support Silvertel Ltd

@wigouche, Thanks a lot, It is first class Apps Support.

A Lesson to Learn is always go to next level support, here is level 2 support. believe or not there is level 3 support for this case which is POE controller IC Apps Support. Since level 2 does fantastic job...

@Wigouche,

I received almost exactly the same mail from silvertel? Did you answer it? :-)

Thanks for the fast explanation and solution, happy to hear that it can be solved easily. I'm now searching for the right capacitor on some old elektronics as i do not have these component laying around. :-P

I'll try it out and post my result here.

i found a 100µF 16v capacitor on an old elektronic board. Should i use a 100µF 6V or is the 100µF 16V also good to use?

I learned elektronics 10years ago. But only the basics. I actually don't know what this capacitors do exactly. If i'm not midstaken they load an unload a current rapidly. But does this mean that if i use the 16V cap that it loads and unloads 16V?

No, the cap is just rated to work at voltages up to 16V. It will fine for 5V. 470uF might a bit much for the system to charge up initially, you might see some odd behavior when the power is first turned on.

thanks alot the fast reply,

it was a 100µF 16V i found, not a 470µ. (edited my post above) made a little mistake

Thanks for the reply wigouche

As a quick question will the Ag9705 work or will i have to rip it out and then order a 9605? It is funny that i just got mine from you guys this week :)

Thanks

Davey

Solved! Thank you everyone.

Soldered the cap onto the PoE board itself. See attachments.