Etherten ethernet stopped working when powered by POE

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]
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sumnerboy
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Etherten ethernet stopped working when powered by POE

Post by sumnerboy » Tue Oct 21, 2014 8:20 pm

I have a couple of your Ethertens powered by POE from one of your 4-channel POE Mid Span Injectors. They have both been working just fine for the last month or so.

Then all of a sudden last night both of them dropped off the network. They were both still receiving power and there was nothing in my DHCP logs indicating they weren't even trying to connect to my IP network.

I am only using two of the ports on my mid-span injector so I tried different ports on that, but no difference. I then noticed if I unplugged one of the Ethertens, the other one would operate OK after a reset. As soon as plugged in the second Etherten both would drop off.

I then plugged the second Etherten into my laptop USB to make sure the sketch was ok and noticed it started working again, along with the other one. As soon as I unplugged the USB cable they both dropped off again.

I have just noticed that when being powered by POE the ethernet LEDs are not being lit at all on the problematic Etherten, but the power led and D13 led are shining bright. As soon as I plug it back into the USB the ethernet leds come to life and everything starts working.

Any ideas what could be wrong here? Is it possibly a faulty POE injector, or something wrong with this Etherten perhaps? Very hard to tell from a far I know, but just wondering if you had seen or heard of anything like this before?

sumnerboy
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Joined:Thu Aug 28, 2014 8:58 pm

Re: Etherten ethernet stopped working when powered by POE

Post by sumnerboy » Tue Oct 21, 2014 8:34 pm

As soon as I unplug Etherten B from the USB supply (therefore powered by POE only) all the ethernet leds go out on both Etherten A and B and they both drop off the network.

If I plug Etherten A into the USB supply then the ethernet leds come on but Etherten B is still dead. Plugging Etherten B into the USB supply causes the ethernet leds to come on for both devices and is the only way I can get both to work on the network.

Is it possible there is something wrong on Etherten B that is shorting out something in the mid-span injector? Very very weird - since it was all working fine up until last night and nothing has changed in terms of DHCP server, network config, or either of the sketches.

angusgr
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Re: Etherten ethernet stopped working when powered by POE

Post by angusgr » Tue Oct 21, 2014 9:26 pm

Hi sumnerboy,

What an unusual combination of symptoms! Sorry to hear your setup stopped working smoothly.

Do you have access to a multimeter? If so, can you measure the voltage on the V- and V+ pins of the PoE regulator on each EtherTen?

Is the regulator on either EtherTen getting unusually hot? Take care not to burn yourself on the offchance it is!


Angus

sumnerboy
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Re: Etherten ethernet stopped working when powered by POE

Post by sumnerboy » Tue Oct 21, 2014 10:05 pm

Hey Angus,

I do have a multimeter but I am not sure which IC is the voltage regulator on the Etherten.

I took the jumpers off and measure the voltage coming in across the incoming POE and it was 8.1V. The voltage across the VCC + GND pins (without jumpers) was 4.27V - so this will be what is being supplied by the USB cable.

When I reconnect the jumpers (VCC -> (+) and GND -> (-)) I see 5.22V across.

Thanks for assisting!
Ben

angusgr
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Re: Etherten ethernet stopped working when powered by POE

Post by angusgr » Tue Oct 21, 2014 11:32 pm

Hi sumner,

Sorry, I didn't explain very well at all. However it sounds like you made the measurements I was thinking of!

What voltage power adapter do you have attached to the PoE midspan injector? 8.1V out of the PoE injector (as measured at the + - pins with no load attached) is within spec, but if this drops to 5.2V when you attach the load then this is too low (minimum 7V VIn for EtherTen).

Can you please measure the voltage at the PoE midspan injector (with and without loads attached) and compare? The voltage at the PoE injector should be in the range 7-20V to be compatible with the EtherTen VIn requirements (recommend 7-12V).

If the midspan injector power adapter's output has degraded a little as it has aged then this may explain the large drop (to below minimum voltage) when you attach the loads.


Angus

sumnerboy
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Re: Etherten ethernet stopped working when powered by POE

Post by sumnerboy » Wed Oct 22, 2014 12:52 am

I have a 9V wall wart supplying the POE injector. Without anything plugged in it is reading about 9.4V across the input pins.

When I attach the *good* Etherten it drops to about 9.3V. If I attach the *bad* Etherten it drops to 9.0V.

How long should these POE injectors last? Is this a known issue with the adapter output degrading?

Makes sense if this is a voltage issue I guess. Need to get my hands on a 12-15V supply...

angusgr
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Re: Etherten ethernet stopped working when powered by POE

Post by angusgr » Wed Oct 22, 2014 9:35 pm

I think that's probably worth trying. There will be some voltage drop due to the resistance of the cables as well.

It may be that EtherTen #2 draws slightly more current for some reason (higher resistance in its cable, something that's attached to it, normal variation between the parts onboard the two) and this just happens to drop the input voltage below the minimum input threshold.

12V is probably a happy medium to try. Get an adapter with 500mA current capacity if you're just powering the EtherTens and nothing else, probably 1A otherwise (and I'd recommend 1A anyhow if you can get it.)


Angus

sumnerboy
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Re: Etherten ethernet stopped working when powered by POE

Post by sumnerboy » Thu Oct 23, 2014 7:21 pm

Thanks Angus - I have just ordered a 12V 2A AC-DC wall wart so will try that when it arrives.

sumnerboy
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Re: Etherten ethernet stopped working when powered by POE

Post by sumnerboy » Tue Oct 28, 2014 7:52 pm

Just a follow up - I bought a new 12V 2A adapter and now both Ethertens seems to working fine. Thanks for your help Angus.

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