Power over Ethernet (PoE) fault finding - Page 1
Forum section: electronics / beginners

author: Mad Professor
author_rank: Regular Contributor
timestamp: March 25, 2016, 08:47:19 am
content: Hi All.I am hoping that there might be somewhere here with more hands on knowledge regarding Power over Ethernet (PoE).I am looking for some help and advice with regards to myHikvision DS-2CD2032-IandNetgear GS108P.My understanding is that the Netgear GS108P ports 1 to 4 support PoE, and 5 to 8 do not support PoE.Looking at the manuals, both the camera and the switch support PoE 802.3afI am wanting to install the above camera and power it via PoE. But it seems that it is a no go, I have tried each of the PoE ports.I can power the camera via an external 12volt supply and the camera will work just fine, But nothing via PoE.Where the camera is due to be installed is less then 15m of cable from the Netgear GS108P. My RJ45 cable tester shows no problems with the cable, but to be sure I even plugged in a 0.5m cat5e, and still no go.I do not have any other PoE devices to be able to test the Netgear GS108P, and I have no other way of supplying PoE to the camera.While trying to reserch on how PoE works I came across the followinghttps://portal.chippc.com/support/downloads/files/PoE_and_IEEE802_3af.pdfQuoteCan anyone here think of anything else that I can try before I have to start spending out more money.Thanks for your time.Best Regards.

author: han
author_rank: Frequent Contributor
timestamp: March 25, 2016, 10:11:06 am
content: Is it easy to take the camera apart?Probably the camera didn't have PoE module installed (or just damaged one)

author: Kohanbash
author_rank: Regular Contributor
timestamp: March 25, 2016, 02:41:20 pm
content: HiAs you said the cameras is 12V. The spec sheet says it is rated for 12V+/-10%. (The spec is a bit unclear and might just refer to the power brick that it ships with)You should verify the voltage coming out of the switch. It might be higher (such as 48V).If that is the case you can use a "normal" switch and an external POE injector at 12V

author: PA0PBZ
author_rank: Super Contributor
timestamp: March 25, 2016, 03:04:20 pm
content: Quote from: Kohanbash on March 25, 2016, 02:41:20 pmPoE is 48 volts, but the switch will not enable PoE before handshaking with the consumer, so there is nothing to measure before you connect a proper PoE consumer.There is nothing in the manual of the camera about PoE except that it should support it, and there is no manual for the switch that I could find. Looks unmanaged so I guess there is no PoE on/off setting. Failing anything else there are PoE to 12V convertors/adapters, maybe that is the easiest solution.

author: true
author_rank: Frequent Contributor
timestamp: March 25, 2016, 09:50:08 pm
content: Quote from: PA0PBZ on March 25, 2016, 03:04:20 pmOn the former, yes, it is a PoE model. All 2032s support PoE.On the latter, yes, it is an unmanaged basic PoE switch.Is this a new switch? We've had several similar switches, including this model, fail in the field - basically the PSU craps out and can't supply PoE. Sometimes switching still works (uplink connection lights flash like normal), and sometimes the switch doesn't, or the PSU is oscillating...Best to try another camera or another switch. If you have neither, see if you can borrow one, or get a cheap PoE injector and see if the camera works.

author: Cliff Matthews
author_rank: Unknown
timestamp: March 25, 2016, 10:53:56 pm
content: I have the Netgear 8 + 8 port unit (similar, but with 65-watt total power budget). The specs on yours shows max of 50-watts, so you could test the power supply with a 100-ohm load to see if it can deliver 24-watts. You can use a 10-watt resistor for a few of seconds in parallel with a volt meter.

author: bingo600
author_rank: Super Contributor
timestamp: March 26, 2016, 07:03:16 am
content: I think i read somewhere , that there are 2 wiring standards for PoE (how the wires/power is connected to the strands).Could you be hit from that ?/Bingo

author: Mad Professor
author_rank: Regular Contributor
timestamp: March 26, 2016, 09:07:48 am
content: Thank you for your replies.I have been leaning more towards the switch being at fault.I have just noticed that the power LED on the front of the switch also does not come on.I purchased the switch around two years ago, as I knew I would be adding PoE cameras to the network at some point in the future.As a switch I have not had any problems with it, but as I have not used the PoE I do not know if this has not been working from day one.I have now pulled the switch out of service and replaced it with a standard switch so I can do some bench testing.Last night I opened up the switch just to check voltages, I am finding the right voltages where I am expecting to find them.The PoE section of the switch is controlled / powered by a BroadcomBCM59101BKMLGQuad Integrated IEEE 802.3af-Compliant Controller.At this point in time I can only find theBCM59101 Product Brief, but I would also like to have a read over the datasheet.I have tested all the smd fused for continuity, and all four test ok.I then moved on to testing all the smd diodes, I have found two diodes that read continuity is both directions (dead short), D8 top layer and D15 bottom layer.D8QuoteI think this might be a 5.1V or 5.6V Zener Diode depending on what datasheet I look at.D15QuoteI think this might be a Schottky Barrier Rectifier.My datasheet hunting skills are very much lacking, could someone please confirm the details for D8 and D15.As I said above the Power LED is not coming on, The pcb traces for this LED goes to the BCM59101.I found this video on youtube. at approximately 1:46 power is applied to the unit, the Power LED comes on, and all the port link led's blink on and off again.https://youtu.be/HNbFMr9YeC4?t=1m43sWhen I apply power to my unit, the power LED does not come on, But all of the link led's do blink on and off again.So it seems that the switch is indeed the issue.Now it's a case of do I send the unit back to netgear, as the ProSafe range has aLifetime Warrantyor do I try and repair the unit.What are your thoughts?Thanks again for your time and help.

author: BradC
author_rank: Super Contributor
timestamp: March 26, 2016, 11:39:31 am
content: The Poe light won't come on until it has handshaked with the device. My experience with Hik stuff would lead me to blame the camera before the switch. You can test it by shoving 48v into the non-used pairs on the camera data cable. Check the spec for pins and polarity. I used that to power 4 cameras before I bought a real switch. Just pulled the pairs out of a cheap patch cable and shoved them into a psu. The camera should support both a and b variants of Poe.

author: dfmischler
author_rank: Frequent Contributor
timestamp: March 26, 2016, 01:15:06 pm
content: My experience with both Netgear switches and Hikvision cameras would lead me to get a better switch. I found some HP J8762A switches on ebay for about $40 each shipped, but the fans are pretty loud if you are going to be near it. I also have Cisco SGE20x0P (also loud) and SG300-28P switches, and they work well.