PoE: Kaboom?

Hi All,

I have a customer that likes to do his own Ethernet cabling.
He is installing a bunch of PoE IP cameras and PoE VoIP phones.

Now I can't even imagine the PoE injector spec not having
over current (short circuit) protection in the spec. so
I am not ever going to look.

But do implementators actually follow the spec.?

If he goofs the cabling, will there be any damage to the PoE
injector port if the cable is shorted out?

How about what he hooks it to: flashing lights, bad smell,
kaboom, laughing computer consultant?

I did see a PoE tester, but it was ~$200.

Your thoughts?

-T

On 2019-06-04 11:48, T wrote:
Hi All,

I have a customer that likes to do his own Ethernet cabling.
He is installing a bunch of PoE IP cameras and PoE VoIP phones.

Now I can't even imagine the PoE injector spec not having
over current (short circuit) protection in the spec. so
I am not ever going to look.

But do implementators actually follow the spec.?

If he goofs the cabling, will there be any damage to the PoE
injector port if the cable is shorted out?

How about what he hooks it to: flashing lights, bad smell,
kaboom, laughing computer consultant?

I did see a PoE tester, but it was ~$200.

Your thoughts?

-T

All low-cost Chinese PoE injectors I've seen do NOT follow the spec but
are just a 48V PSU, a few inductors and two RJ45's. There is no PSE side
PoE protocol controller, so connecting to a camera without PoE (but with
the usual 75 Ohm Bob-Smith terminations) may cause severe problems.
Current limiting is only the limiter of the PSU. Smoke will escape from
the camera.

It is easily checked with a $5 DMM: measure the output voltage when no
load is connected, it should be just a few volts. Connecting a 25kOhm
resistor load should cause the controller to output 48V (for at least a
few seconds).
Search Google for wiring pinout.

Arie

T wrote:
Hi All,

I have a customer that likes to do his own Ethernet cabling.
He is installing a bunch of PoE IP cameras and PoE VoIP phones.

Now I can't even imagine the PoE injector spec not having
over current (short circuit) protection in the spec. so
I am not ever going to look.

But do implementators actually follow the spec.?

If he goofs the cabling, will there be any damage to the PoE
injector port if the cable is shorted out?

How about what he hooks it to: flashing lights, bad smell,
kaboom, laughing computer consultant?

I did see a PoE tester, but it was ~$200.

Your thoughts?

-T

https://en.wikipedia.org/wiki/Power_over_Ethernet

"Stage Action Volts

Detection PSE detects if the PD has the correct 2.7–10.1
signature resistance of 19–26.5 kΩ
"

"PSE may deny any PD drawing more power than max allowed by PSE"

The article further describes the various protocol(s) supported.
I would guess that the probing can detect a "dumb" device
not needing POE.

*******

https://www.amazon.ca/WS-PoE-Tester-.../dp/B00SCMTMVG

https://www.poetexas.com/products/po...etector-bundle

The Amazon photo might still have had the protective peel-off display
cover on it, while running.

And this is their way of "proving" they are in Texas. Otherwise, their "About"
entry doesn't actually give a street address. I must have missed it.

https://www.poetexas.com/blogs/news

Paul

On 6/4/19 7:00 AM, Arie de Muynck wrote:
On 2019-06-04 11:48, T wrote:
Hi All,

I have a customer that likes to do his own Ethernet cabling.
He is installing a bunch of PoE IP cameras and PoE VoIP phones.

Now I can't even imagine the PoE injector spec not having
over current (short circuit) protection in the spec. so
I am not ever going to look.

But do implementators actually follow the spec.?

If he goofs the cabling, will there be any damage to the PoE
injector port if the cable is shorted out?

How about what he hooks it to: flashing lights, bad smell,
kaboom, laughing computer consultant?

I did see a PoE tester, but it was ~$200.

Your thoughts?

-T

All low-cost Chinese PoE injectors I've seen do NOT follow the spec but
are just a 48V PSU, a few inductors and two RJ45's. There is no PSE side
PoE protocol controller, so connecting to a camera without PoE (but with
the usual 75 Ohm Bob-Smith terminations) may cause severe problems.
Current limiting is only the limiter of the PSU. Smoke will escape from
the camera.

It is easily checked with a $5 DMM: measure the output voltage when no
load is connected, it should be just a few volts. Connecting a 25kOhm
resistor load should cause the controller to output 48V (for at least a
few seconds).
Search Google for wiring pinout.

Arie

Thank you!

On 6/4/19 8:10 AM, Paul wrote:
T wrote:
Hi All,

I have a customer that likes to do his own Ethernet cabling.
He is installing a bunch of PoE IP cameras and PoE VoIP phones.

Now I can't even imagine the PoE injector spec not having
over current (short circuit) protection in the spec. so
I am not ever going to look.

But do implementators actually follow the spec.?

If he goofs the cabling, will there be any damage to the PoE
injector port if the cable is shorted out?

How about what he hooks it to: flashing lights, bad smell,
kaboom, laughing computer consultant?

I did see a PoE tester, but it was ~$200.

Your thoughts?

-T

https://en.wikipedia.org/wiki/Power_over_Ethernet

Â* "StageÂ*Â*Â*Â*Â*Â*Â* ActionÂ*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â* Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â* Volts

Â*Â* DetectionÂ*Â*Â*Â* PSE detects if the PD has the correctÂ*Â* 2.7–10.1
Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â* signature resistance of 19–26.5 kΩ
Â* "

Â* "PSE may deny any PD drawing more power than max allowed by PSE"

The article further describes the various protocol(s) supported.
I would guess that the probing can detect a "dumb" device
not needing POE.

*******

https://www.amazon.ca/WS-PoE-Tester-.../dp/B00SCMTMVG


https://www.poetexas.com/products/po...etector-bundle

The Amazon photo might still have had the protective peel-off display
cover on it, while running.

And this is their way of "proving" they are in Texas. Otherwise, their
"About"
entry doesn't actually give a street address. I must have missed it.

https://www.poetexas.com/blogs/news

Â*Â*Â* Paul

Thank you!