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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 |
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#2
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PoE: Kaboom?
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 |
#3
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PoE: Kaboom?
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 |
#4
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PoE: Kaboom?
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! |
#5
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PoE: Kaboom?
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! |
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