Let the smoke out....

The EtherTen combines an Uno-equivalent Arduino-compatible board and Wiznet-based Ethernet support, along with a microSD card slot and Power-over-Ethernet support. [Product page]
andrewr
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Let the smoke out....

Post by andrewr » Fri Jan 23, 2015 6:06 am

Hi guys,

Made a (probable) newbie mistake today thats probably going to be costly....

Installed a 802.3af PoE regulator onto an EtherTen, plugged into a PoE switch and watched happily it start up.

Disconnected the ethernet cable, plugged in the USB lead, installed a sketch (basic webserver), brought the serial monitor up, all good. Happy Andrew.

(you can see where this is going....) Plugged the ethernet lead back in..... :o :oops: :-(

Unsoldered the PoE board to try and power the EtherTen via the serial port or the 2.1mm jack and it looks like its dead....

Unless I'm going blind, there's no caution warning on any documentation saying that you can't have the ethernet lead (supplying PoE) and the USB lead plugged in together - is this true? I'm guessing to do a serial monitor it'd have to be plugged into a non-PoE port on my switch, which is a pain in the butt.

I guess the EtherTen is kaput - would the 802 board be kaput as well?? $95 mistake if it is....

Cheers,

Andrew

andrewr
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Re: Let the smoke out....

Post by andrewr » Fri Jan 23, 2015 8:22 am

A bit of further info....

I noticed another thread on here about power issues and it looks like I may have had the same thing.

The PoE switch I was feeding it by is a TP-Link TL-SG1008P and it appears the -ve of the 48V supply feeding it is hooked to the mains earth. I was using one of the USB ports on my PC, so it would assume I've managed to get some sort of ground loop or something due to the supply of the TP-Link not being floating.

angusgr
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Re: Let the smoke out....

Post by angusgr » Wed Jan 28, 2015 9:31 pm

Hi Andrew,

Sorry for the slow reply. This does sound like some kind of ground loop issue, even though the PoE modules are supposed to allow for this - it shouldn't be a problem.

Was the TP-Link PoE power supply on a different circuit or on a long cable from the EtherTen and the computer?


Angus

andrewr
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Re: Let the smoke out....

Post by andrewr » Thu Jan 29, 2015 8:36 pm

Hi Angus,

No, it was plugged into the same power board as the PC and connected to the EtherTen via a 1.5m Cat5 lead.

Cheers,

Andrew

andrewr
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Re: Let the smoke out....

Post by andrewr » Wed Feb 04, 2015 10:52 am

Just to add a bit further to this thread for everyones amusement and information....

I've checked another TP-Link TL-SG1008P that we had at work and it was the same - the -ve of the 48vdc supply was hooked to the mains earth.

Checking a Linksys LGS108P that we also had, the DC supply on it is fully floating.

Moral of the story.... be possibly wary of using a TP-Link POE switch to power a EtherTen via POE.

Stylmast
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Re: Let the smoke out....

Post by Stylmast » Fri Feb 06, 2015 1:50 am

I have come across something similar, but mine was to do with using the DC supply jack & then plugin usb from a laptop with mains connected and I fried the board, it was only a Eleven so not to hard on the wallet. Work great with out the AC power connected, isolated from earth.

As a marine electrician I have always wondered & never found a good response as to why some systems are connected to earth and not others.. Capacitor coupled works most of the time but direct connect causes problem as above..

I try to run my DC systems above earth( Floating ), that way it takes to connection to earth to cause smoke. LOL It may have something to do with old ways of doing thing ( just a guess ).

Also as a side note - AC systems use MEN which already ties one side of the system to earth, so all you need is one fault to cause a problem or smoke. Hence the RCD is used to monitor the down stream side of the system. Some systems are ground or floating which requires 2 faults to cause a problem.

andrewr
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Re: Let the smoke out....

Post by andrewr » Fri Feb 06, 2015 9:04 am

Hi Stylmast,
Stylmast wrote: I have always wondered & never found a good response as to why some systems are connected to earth and not others.. Capacitor coupled works most of the time but direct connect causes problem as above..
... and TP-Link support are struggling with my question: (email sent with attached jpg)

"L,N & E being Line, Neutral and Earth (Protective Earth) of the mains supply input, +ve and -ve being positive and negative of the 48VDC output. Is there supposed to be a connection between the Earth of the Mains Supply Input and the -ve (negative) of the 48VDC output? "

... to say their response was not confidence inspiring would be the understatement of the year!!

"I am really sorry for that the question is out of the available service scope. we have no idea about the answer."

:shock: :o

Cheers.
Attachments
TP-Link POE LV supply 2.jpg

Stylmast
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Re: Let the smoke out....

Post by Stylmast » Sat Feb 07, 2015 12:48 am

That was a great answer from them. NOT.. More than likely the support is run by people with a limited knowledge from the tech side of things, which doesn't help. I think that there is ment to be a connection to earth as it would likely have something to do with our standards. But trying to get an answer on that would be very hard. The items with out a direct connection to earth are designed for international markets and are are more likely to also be multi voltage. Just my guess...

I think that the direct connection may cause more problems than it fixes for the more tech savy people out there like most of the people that are on here. My 2 cents..

angusgr
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Re: Let the smoke out....

Post by angusgr » Sun Feb 08, 2015 11:25 pm

Hmm yes that's not a great reply.

I've found it's pretty common for higher voltage/current AC/DC adapters to come with a 3 pin earthed AC inlet, and to have the output DC -ve "ring" earthed. For example most laptop adapters do this.

An anecdotal example, for a while in the late 2000s Apple shipped (from memory) an earthed 90W adapter and an unearthed 60W adapter for Macbook Pro and MacBook models, respectively. They looked identical at a glance. If you plugged the 60W MacBook adapter into a MacBook Pro then you could sometimes feel a tingle on the metal laptop surface due to the floating output! (Also the 60W adapter got really hot!)

I don't know if grounding such adapters is an Australian Standard requirement or just a common safety design feature.

Regardless of whether the output is grounded, it shouldn't make a large difference to the EtherTen itself. The RJ45 jack and the PoE 802.3af module are both supposed to be 1500V isolated, so no matter what is happening on the RJ45 cable the ground of the EtherTen (which is also the ground of the USB cable) should be isolated.

So I'm still at a loss to explain this. We might get some more clues when the module arrives here (no sign yet, hopefully today.)

I did find this interesting discussion on the IEEE802 mailing list about how they decided _not_ to include grounding requirements in the 802.3af standard: http://www.ieee802.org/3/power_study/em ... 00957.html


Angus

Stylmast
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Re: Let the smoke out....

Post by Stylmast » Sat Feb 14, 2015 5:43 am

I just stuffed up.. I smoked an Ether Ten. I had the dc jack supplying power to the board and wanted to fault find as to why I was getting a code error. I plugged in the serial lead buy I had the laptop charging and out came the smoke... Sh.......!!!!

This is a normal state for me as I require the board to be powered as the next step involes adding data logging to be added I don't what to keep having to reset the data every time. Is there another way to check code in real time before putting it onto the sd card or another way of doing this all together with out the sd card. ( I will be heading to a network data logging ) but
I want to try it first on an sd card. Maybe best to skip this stage. Less change of more smoke.

Is there anything that can be changed in your design to stop this form happening. This is the second board I have fried in this fashion both time by mistake. These board must require above ground power supplier to be safe.

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