HOWTO: WRT54GL DIY INTERNAL POE! *PICS*

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matt0401
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PostPosted: Tue Aug 28, 2007 3:35    Post subject: Reply with quote
Treb, that daisy chain looks cool but how do you provide it with enough power for 3 devices? I only see one spot for a power adapter. Won't there not be enough power to power 3 GL's if you only plug in one power adapter to the daisy chain?
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Treb
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PostPosted: Tue Aug 28, 2007 16:24    Post subject: Reply with quote
matt0401 wrote:
Treb, that daisy chain looks cool but how do you provide it with enough power for 3 devices? I only see one spot for a power adapter. Won't there not be enough power to power 3 GL's if you only plug in one power adapter to the daisy chain?


That wholly depends on the power supply you hook up to the daisy chain. I don't have the power consumption of a GL in my head (Google is your friend).

For the sake of argument lets assume a GL will draw a maximum of 250 milliAmps, then three GL's will draw 750 milliAmps of current. So a 750 milliAmps would be enough theoretically. In the real world having a bit of extra power reserve is recommended. I'd say that a 1000 milliAmps power adapter should suffice in this example.

Trying to draw more current out of a power adapter than it's capable of delivering will (literally!) fry a power adapter. Been there, done that Very Happy.

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matt0401
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PostPosted: Tue Aug 28, 2007 22:52    Post subject: Reply with quote
Ahh okay. See I'm new to electrical engineering. I didn't even know you can use mismatched power adapters with random devices (as long as they fall into certain guidelines).

Basically, what you're saying is: You can use any power adapter with any number of devices as long as the power adapter is capable of providing enough current for all devices it's powering or more, but not less. Even if it provides way more than needed, the power supplies of the devices can step it down.

Is this correct?
Treb
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PostPosted: Wed Aug 29, 2007 6:56    Post subject: Reply with quote
Yes. If a power supply can deliver way more current than the device it's powering actully needs, the power supply won't even break into a sweat.

The above doesn't apply to voltage! Some devices, such as the WRT54G(L), have an internal voltage regulation and can be powered with anything between 5 and 20 Volts. Some devices don't have internal voltage regulation and need to be hooked up to a specific power adapter supplying the correct (pre-regulated) voltage.

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matt0401
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PostPosted: Wed Aug 29, 2007 14:31    Post subject: Reply with quote
Thanks for the info, Treb.

I have one more question. When using one power supply to provide power to multiple routers should they be wired in series or parallel?
infusion
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PostPosted: Wed Aug 29, 2007 16:32    Post subject: Reply with quote
Parallel! Very Happy
Treb
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PostPosted: Wed Aug 29, 2007 18:18    Post subject: Reply with quote
Parallel indeed. A daisy chain is parallel too.
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robert-e
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PostPosted: Wed Aug 29, 2007 18:48    Post subject: Reply with quote
Hi,
The amount of voltage drop is proportional to both current AND length of wire, to the more routers you hang off the lan cable, the shorter the maximum length of that cable.
For example, suppose the max length for one router is 300 feet, then if you hang 3 routers off the end, the cable length can only be a max of 100 feet. The only thing that could help this is to use bigger conductors for the lan cable, or use a pair of wires in parallel in the Positive and Negative leads (in the lan cable).

Regards,
Bob
Blackraven
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PostPosted: Thu Aug 30, 2007 12:06    Post subject: Reply with quote
Anybody has experience with hacking a NIC card so that it powers the WRT?
I want to do this to my laptop, so I can power my client-mode router over it.

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TomSelleck
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PostPosted: Thu Aug 30, 2007 13:13    Post subject: Reply with quote
Blackraven wrote:
Anybody has experience with hacking a NIC card so that it powers the WRT?
I want to do this to my laptop, so I can power my client-mode router over it.


That's an interesting idea. You could solder power to the correct contacts on the NIC. You could build your own molex connector to have the PC's power supply power the router. If you will only be using that one PC with the router, it seems kind of excessive. You could just get a USB client adapter.

The scenario would be marginally more useful if the router was in client-bridge-mode. One PC powers the router but several PC's use it.
toysareforboys
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PostPosted: Thu Aug 30, 2007 13:29    Post subject: Reply with quote
Blackraven wrote:
Anybody has experience with hacking a NIC card so that it powers the WRT?

Laptop? Hmmm. Not too sure. You'll need to feed the network port with power from the power port on your laptop. You could do it internally probably. Check the output on your laptop power adapter, if your using a Linksys router anything 9 to 19 volts should be fine for your POE setup.

Now using a desktop computer to power the linksys, that's a great idea. If you're using a Linksys router, you can power it internally in your computer, right off your computers power supply! Yellow and Black wire to the corresponding pairs of pins on the back of your nic's network port. The back of your nic will look exactly like the back of the WAN port in my picture.

Now, if you need to run a few routers off it, your computers power supply has more then enuff juice Smile.

-Jamie M.
adx
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PostPosted: Sat Sep 01, 2007 1:00    Post subject: Reply with quote
Can't find the exact power consumption of WRT54GL. So, can we use one 12V 1000mV linksys adapter to power up 2 unit of WRT54GL? If can, how long can we pull the cat5 cable from the first unit to the second? What about xmit power, is there any effect if we use 84mV for both unit?
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toysareforboys
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PostPosted: Sat Sep 01, 2007 1:05    Post subject: Reply with quote
An electrical guy friend of mine measured my GL's current draw at 420mw, wireless set at 84, under full load (4 PC's transfering files to eacher, 4 wireless clients), powered over a 100ft CAT5 cable. Current draw would be a little less on a shorter cable, a little more on a longer cable.

So two off your Linksys's 1000mw adapter should be fine, depending on the cable length.

-Jamie M.
JN
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PostPosted: Sat Sep 01, 2007 17:27    Post subject: Reply with quote
toysareforboys wrote:
An electrical guy friend of mine measured my GL's current draw at 420mw, wireless set at 84, under full load (4 PC's transfering files to eacher, 4 wireless clients), powered over a 100ft CAT5 cable. Current draw would be a little less on a shorter cable, a little more on a longer cable.

So two off your Linksys's 1000mw adapter should be fine, depending on the cable length.

-Jamie M.
Actually, I wonder if I could get a buffalo WHR-G54S to run off a USB port's power?
robert-e
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PostPosted: Sun Sep 02, 2007 21:08    Post subject: Reply with quote
toysareforboys;
Im am not sure how your electrical friend measured the current on your linksys...I measured mine (twice) and got 220 MilliAmps (not mv) without a lan cable attached and 225 ma with the lan cable connected. I used a meter accurate to .1% in series with the 12 volt Linksys power adapter. The router was running 102 mw of power on the radio. This would indicate you should be able to power at least 2 routers (possibly 3) routers with one 1000 ma Linksys power supply.
Regards,
Bob
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