Making my own PoE switch

B

Basjke

Getting the hang of it
Jan 5, 2017
151
22
I have purchased 6 piece HAC-HFW2221R-Z-IRE6, and will use Cat5 wire to connect.

Therefore I have purchased the following video balun.

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Cameras came without power supply, which I think is standard.

I know they are are 12v but I can't find anywhere how many Amp the power supply should be.

I read somewhere that a PSU of 12V 2.5A should be used, but in the spec I read maximal power consumption is only 8.6 Watt, so less than 1A

Since the video balun I purchased can transfer the power over the Cat5 I want to build my own kind of PoE.

When I look at PoE switches I notice that for a 12V camera they use 48V switches, what I don't understand.

My idea was to buy a power supply 12VDC 15 A ( 2.5A x 6) , or 2 x 7.5A, and then connect 6 DC plugs to the output of the power supply. So that would mean that every camera would get 12V 15A or 7.5A depending if I use 1 or 2 power supplies.

Would this work the way I intend, or am I dreaming ?


Edit : should have done some more research before posting, because a Cat5 wire can not handle more than 1.5A, so my video baluns are kinda waste of money since I will need separate power supplies anyway.
 
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That's the reason for the 48V. The standard POE (802.3af) can supply 12V at 12W at the destination from 48V due to line loss and conversation. POE+ (802.3at) can provide 25W at 12V.
I would use a POE switch and one of these (PoE Splitter - TP-Link) at the destination to get the voltage that you require.

EDIT: I notice that the adapter says 12V-36V MAX so this may not actually work.. :(
 
Do not mix up real PoE according to 802.3xx standard and Passive PoE injection those are two different things.

The adapters you bought are Passive PoE Injectors meaning YOU inject power thru some 12V powersupply (can be as many amps you want, the camera will only use what it need).

Real PoE 802.3xx cameras need real PoE 802.3xx switch or power source which is indeed 48V, the reason of 48V is that is can suffer or voltage drop (usually the powered device really need 12V max oe less) and also higher voltage mean you can go down with the amps to provide same power at the end, remember the law P = U x I
 
Dodutils said:
The adapters you bought are Passive PoE Injectors meaning YOU inject power thru some 12V powersupply (can be as many amps you want, the camera will only use what it need).
Click to expand...

I understand the camera will use only the amps it need, but I think a Cat5 wire is limited to something like 1.5amp, and I also don't know how much the camera actually need.

In the spec it says maximum 8.6Watt power consumption, which is 0.71Amp, but on Ebay listings I read recommendations for a 2.5Amp power supply.

Is this because of the motorized lens?

Anyone can tell me the current requirements for this camera?
 
To be clear, the OP does not have a network camera, its a CVI camera...so there is no "switch"..
 
12V with 8.6W max mean 0.71A max (that is the real values from Dahua web site I don't understand why you can't find them it's on their camera's tech spec page)

http://www1.dahuasecurity.com/fr/products/hac-hfw2221r-z-ire6-1224.html

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Cat5 cables are supposed to be 24AWG minimum so 0.57A per wire (6.8W) and as your plug provide 2 pairs of +/- power wires it could handle 1.14A@12V=13.6W

But you may find 22AWG Cat5/6 cables that allow 0.96A per wire and then you'll have 23W if your dongle internally split/join the power over 2 pairs like shown on the little schema they have printed on them.

But you also have to be aware about the voltage drop depending the length of you cable so if the camera need can draw 8.2W@12V mx and if only 9V reach the camera (min allowed voltage 12V-25%) then it may require 2A to reach 8.2W max value.

Question, why did you buy Analog cameras ?
 
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Basjke said:
I did find this, as I posted in my previous message, but in my book 12V 8.6 W means 0.71A and not 1.4A.
8.6W / 12VDC = 0.71A
Why do sellers recommend 2.5A if 0.71Ais what it really needs?
Click to expand...

oh my bad about the math I was not awake this morning I inverted the calculations (updated my comment) ;-)

Do not take care about what they recommend but as I said you can use a 12V/2.5A power supply if you want, the camera will take what it needs (on contrary of voltage for which you cannot provide higher voltage than maximum allowed/supported by the camera). and/or the gauge of the wire will limit the current physically.

But sometime resellers recommend higher value just to avoid possible poroblem due to power peaks some lower power transformers may not handle properly and then make the device crash, or simply they do recommend it because it's higher priced ;-)
 
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Basjke said:
Because it was much cheaper than the same spec ( motorized varifocal) in IP camera, and they are 2MP, which means better picture at night
Click to expand...
But you'll get worst picture than real 2MP IPCam because of analog convertion.
 
Basjke said:
Not so sure about that, going by the comments of bigredfish, who owns this camera and IP cameras as well.
Click to expand...

Video quality is indeed surprisingly good for analog, I went to IP cam for a long time ad never went back to analog since then but looks like they improved a lot.
 
Dodutils said:
But you'll get worst picture than real 2MP IPCam because of analog convertion.
Click to expand...

HDCVI cams today, particularly the Starlight versions, are virtually identical in IQ as their 2MP IP counterparts. The indeed now have 4-8MP and 4K in HDCVI.

Perhaps under very fine expert observation there could be a difference, but I dare most to see a difference in IQ if I didnt tell you they were HDCVI. See attached
 

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