Power over ethernet

[wesleyw]

Does anyone know if there is a PoE based TFT out there? I know you can get Think Clients that are but I was wondering about screens?

 

 

Wes

[gwendes]

ooooo...

You could probably inject the monitor's PSU over ethernet and then collect it the other end.

Would be cool if you could get VGA too - poor little cat5!

Love the idea - what are you gonna do with it?

[wesleyw]

Well I was thinking of installing around 50 points per room and setting up Thin Clients and TFTs to gain power and data but I haven't been able to find anything for TFTs some thin clients only use about 4w but TFTs are more like 30w so I'm not sure if it's possible or not?

 

 

Wes

[srochford]

As far as I know, you can't do what you want at the moment but I've read about various attempts to change the PoE standard to allow enough power down the cable to power something like a laptop.

 

Not sure if this would give you enough for a TFT - I'm guessing that the idea is to get enough current to charge the battery slowly rather than to power the whole machine but all sorts of things are possible :-)

[Geoff]

The Specs for PoE limit the wattage for each port to 12.95W, this is insufficient to run a TFT.

 

http://en.wikipedia.org/wiki/Power_over_Ethernet#Power_levels_available

[gwendes]

Here's a 12W TFT

 

http://www.sharp-world.com/corporate/info/rd/tj1/pdf/6.pdf

 

and that's old (1997)

 

Theoretically possible but never been done ASAIK

[plexer]

The notes section at the bottom of that wikipedia article is the most interestnig.

 

Using 2 pairs for + and 2 pairs for - you could provide is 72W taking into account voltage drop on a 100m cable you could provide 59W.

 

So it would be possible to run 2 cat5's for each machine poe + data for the thin client from one and power from the other.

 

Ben

[wesleyw]

What sort of a fire risk would it be though? I can just imagine 10 rooms turn on in the morning for instance and the fire brigade are out five minutes later

 

 

 

 

 

Wes

[plexer]

There isn't one if you look at the spec that's what the cable is rated for it won't melt and burn.

 

If you were to use 1 conductor for + and 1 conductor for - and try and run that then it will melt.

 

Would you like me to test it with a 100m of cat5?

 

Ben

[Ric_]

Just looking at this from a different angle... couldn't you just buy extra big dado and stick the PSUs inside? I have done this with some projector installs for the Nuvo speaker amp (it looks very tidy).

[wesleyw]

@ Ric_: I was thinking it would be a cheaper and simpler solution than putting in 25 network points and 25 power points?

 

@Plexer: If you wouldn't mind testing it and letting me know the results that would be fantastic!

 

Wes

[enjay]

allow enough power down the cable to power something like a laptop. Not sure if this would give you enough for a TFT

Not sure what sort of kit you have, but our laptops pull much more juice than the TFTs (heck, my laptop on standby is about the same as my TFT in full swing).

 

I'm guessing that the idea is to get enough current to charge the battery slowly rather than to power the whole machine but all sorts of things are possible :-)

That can't be - if it was sufficient only to charge the battery not actually run the laptop, then it would eventually turn off, as power out would be greater than power in...

[Ric_]

@wesleyw: You would be surprised how little of the cost of putting in dado trunking and power is actually the power. Compare this cost to PoE injectors (approx. £20 each) and the power receiver (don't know how much one of those might be but assume £10)... that's a conservative cost of £750 just for the equivalent of 25 single sockets.

[enjay]

that's a conservative cost of £750 just for the equivalent of 25 single sockets.

Which compares quite nicely against one price I saw for electrical work which was £50 per socket (£1250 for 25).

[plexer]

Poe injector £11 for 3 com ones, plus you need to have 25 sockets at the injecting end to plug them into cascading and multiple trailing leads not recommended so if you've got to put power in you may as well put it in at the desktop.

 

Ben

[wesleyw]

That seems fair enough. Looking at equiping 36 rooms with 25 power points (not sure if it'll be doubles or singles) will also need to look at new furniture for these as well. I thought I'd get all the options covered and hand the now quite sizeable document to the head to look through before we setup a meeting.

 

Wes

[plexer]

Make all power sockets doubles.

 

Ben

[wesleyw]

Depending on the price difference I will they can then plug in their machines and external drives.

 

 

Wes

[plexer]

Price difference should only be the difference in price between a single faceplate and a double one.

 

Wiring is the same.

 

Ben

[Geoff]

Remeber you can get single plug to double kettle lead cables too.

[mrtechsystems]

Geoff I think we call them Y cables m8 lol 8)

[Geoff]

Well whatever, as long as you know what I mean.

 

http://www.scan.co.uk/Products/ProductInfo.asp?WebProductID=488085