Power Over IP Dongles

[Mike]

Not sure if this helps, but if you can hack this into the equation it might get you a cleaner solution:

http://cgi.ebay.com/PROXIM-HARMONY-POWER-S...1QQcmdZViewItem

6 ports are POE and 6 ports are a regular switch if I recall correctly. I am not familiar with all the considerations of PoE but considering something like this was 10 times the price for the panasonic, I thought it might help.

These work with it, so perhaps you could strip out the electronics from the access point and use these. There may be more to it, but perhaps someone is more familiar with this than I.

http://cgi.ebay.com/Proxim-Harmony-802-11a...1QQcmdZViewItem

Hope this helps.

 

[rocco]

Hi, John:
I would agree with Smee. You don't want to use resistors, because, regardless of the power supply, the voltage drop will vary with current draw, and the current draw will probably vary with when you are accessing the camera.

However, you may not need anything in-line. Your 5 volt supply may work fine as is. I did some calculations.

Assuming that your CAT5 is 24 awg, then the resistance should be 2.62 ohms for 100 feet. If a camera draws 200 milliamp, the voltage drop will be about one volt if you use two wires (one each way), and half a volt if you use two wires (two each way).

Chances are your cameras draw less than 200 milliamp, and the lengths are less than 100 feet. The cameras should be fine if you use all four spare wires.

 

[jrfuda]

Smee, I did not realize regulators were so inexpensive.

Here's one I've found: http://www.jameco.com/webapp/wcs/stores/se...roductId=192233 that's only $0.22 each. It's 5V 500mA, and - from what I've read - I need to give it alteast 7V for it to maintain 5V - so I can set the PS to 7.5V.

Now, what do I do with tis thing? Do I put the power to the input & the output to the camera? Does the ground need to be connected to anything? Is it that simple? ...and you mentioned capacitors, what is the purpose of these in the circuit? As you can tell, I don't know much 'bout electronics.

 

[electron]

I simply inject the power into the spare pair, without any extra hardware. My camera is about 175ft away (regular cam tho, no IP), and it measured 12VDC at both the input and output, but smee's point is definitely valid.

 

[smee]

Smee, I did not realize regulators were so inexpensive.

Here's one I've found: http://www.jameco.com/webapp/wcs/stores/se...roductId=192233 that's only $0.22 each. It's 5V 500mA, and - from what I've read - I need to give it alteast 7V for it to maintain 5V - so I can set the PS to 7.5V.

Now, what do I do with tis thing? Do I put the power to the input & the output to the camera? Does the ground need to be connected to anything? Is it that simple? ...and you mentioned capacitors, what is the purpose of these in the circuit? As you can tell, I don't know much 'bout electronics.

Input connects to the 7.5V (or whatever) from the power supply.
Output will be 5V.
You will have a common ground between the power supply, the ground pin of the regulator, and the ground connection to the camera. I.e., the ground pin, the power supply ground, and the camera ground are all connected together.

The capacitors are between the input and ground and the output and ground. They help to smooth out any noise/irregularities in the output voltage.

Something like a 10uF cap between the input and ground and a 0.1uF cap between output and ground should be ok. Note that if you get electrolytic capacitors (and some other types), they are polarized. You need to connect the "-" end to ground.

The capacitors are pretty cheap, too.

 

[smee]

I simply inject the power into the spare pair, without any extra hardware. My camera is about 175ft away (regular cam tho, no IP), and it measured 12VDC at both the input and output, but smee's point is definitely valid.

With a 12V camera, I'd guess that the actual internal voltage required is smaller. There is probably a regulator inside the camera dropping whatever the supply voltage is down to around 5V so it's not as sensitive to the external voltage.

This would be for the camera itself. If there are illumination LEDs, they might be running off the supply voltage (with the current limited by resistors) but they won't be as sensitive to line loss since they are probably running at higher than the required voltage to begin with.

When you measured the voltage at the camera end, was it with or without the camera connected? I'm just curious if the load made a difference.

 

[jrfuda]

The common ground is the (-) of the PS and camera, right? So, something like this:

Also, I've read a bit about heat disapation with regulators, will that be an issue, or is 200mA too little to worry about heat?

I guess I'll need to practive my soldering. I haven't soldered anything in about 3 years!

 

[electron]

I simply inject the power into the spare pair, without any extra hardware. My camera is about 175ft away (regular cam tho, no IP), and it measured 12VDC at both the input and output, but smee's point is definitely valid.

With a 12V camera, I'd guess that the actual internal voltage required is smaller. There is probably a regulator inside the camera dropping whatever the supply voltage is down to around 5V so it's not as sensitive to the external voltage.

This would be for the camera itself. If there are illumination LEDs, they might be running off the supply voltage (with the current limited by resistors) but they won't be as sensitive to line loss since they are probably running at higher than the required voltage to begin with.

When you measured the voltage at the camera end, was it with or without the camera connected? I'm just curious if the load made a difference.

Good point smee, I think I tested it when the camera was still disconnected. I am about to take those measurements again to track down if my camera was destroyed by the lightning. Interesting thread John!

 

[jrfuda]

Here's a kit I've found: http://www.unifiedmicro.com/vr.htm $4.95 each, or 3 for $12.95. A bit more than buying the parts, but may make fabrication easier and the final product neater.

 

[smee]

The common ground is the (-) of the PS and camera, right? So, something like this:

Also, I've read a bit about heat disapation with regulators, will that be an issue, or is 200mA too little to worry about heat?

I guess I'll need to practive my soldering. I haven't soldered anything in about 3 years!

Yes, that's the circuit. I can never remember which pin is which on the 78xx regulators. Just make sure your capacitors are oriented correctly.

The heat generated will depend on the current draw and the voltage drop. The most recent issue of Nuts & Volts Vol 27, No 7 has an article on selecting heatsinks. You should be able to find information online. I'll admit that I usually don't try to figure this stuff out and do it by trial and error. Often, a heatsink isn't required. At other times, I've had regulators get quite warm (ok, uncomfortably warm).

 

[smee]

Here's a kit I've found: http://www.unifiedmicro.com/vr.htm $4.95 each, or 3 for $12.95. A bit more than buying the parts, but may make fabrication easier and the final product neater.

I was going to recommend a similar kit, but it looks like it was discontinued. I'd go for the kit, myself .

 

[jrfuda]

I just ordered 6 of the kits (actually 2-3packs at $12.95 each).

It looks like I was mistaken regarding the power requirements of my cameras. It looks like the included wallwarts are 5VDC 2.5A, and that the cameras draw 900ma - that seems like a lot of juice for a little camera, so maybe it's a conservative estimate. I may have to use 2 power supplies powering 3 cameras each. Fortuneately I already have 2.

 

[gcimmino]

Some additional reading for you..

These are links from when I was researching POE for my Panasonic BL-C10As which are also "not standard" from a POE perspective as they need 9V.

Homemade POE, one for your type of camera:

http://www.eidusa.com/Electronics_Kits_PoE_injector.htm

http://www.wireless.org.au/~jhecker/poe/

Two calculators for cable loss:

http://www.gweep.net/~sfoskett/tech/poecalc.html

http://www.demarctech.com/techsupport/poecalculate.htm

And last is the commercial product that I ended up ordering for the Pana cams:

http://www.ovislink.com.tw/poe.htm

Enjoy

 

[upstatemike]

Great links! Thanks for posting!

 

[jrfuda]

Yes, great links indeed. I really like the kit on the first links, though they're a little expensive - actually might cost more than the POE switch and splitters application I mentioned a few posts up, but a great way to go for a smaller POE application (2-3 POE devices). The other kits look really good as well.

When I'm all done with this, maybe we should all collaborate on a tutorial for here, and maybe that network camera site that a new member runs.