Power Supply for "far-away" UTPs

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IronBeltKen

Lazy Daydreamer
I just installed an additional UTP panel to my NCE PHPro-based layout. Because of the increased cable length, some of my UTP's that are farther away from the command station have become unresponsive. The NCE website says to plug-in a 12VDC - 1amp "wall wart" (NCE p/n P114) power supply in the socket on the rear. Ok, that sounds simple enough...

My question is: Do I need a P114 for every one of the UTP's that are too far away from the command station? Or, since they are daisy-chained together, will a single P114 suffice for the adjacent UTP's in addition to the one where I plug in the P114?

Any feedback is greatly appreciated...
 

kenw

5th Generation Texian
what are the power requirements (usually stated in mW on the label) of the UTPs? a 1 amp power supply = 1000 mw typically, but longer wire runs may decrease that a little depending on the wire size you use.
 

fcwilt

Active Member
Just a reminder:

E = I * R (where E is voltage, I is current in amps, R is resistance in ohms)

P = I * E (where P is power in watts, I is current in amps, E is voltage)

Other forms here:

http://www.onlineconversion.com/ohms_law.htm


So you cannot state categorically that a 1 amp power supply will provide 1000 mW of power.
 

kenw

5th Generation Texian
Well, 40 years in engineering taught me that, but for model railroad purposes it's close enough..... note the word "typically'......
 

fcwilt

Active Member
Well, 40 years in engineering taught me that, but for model railroad purposes it's close enough..... note the word "typically'......
How do you figure that?

For a power source capable of 1 amp but limited to 1000 mW the output voltage would need to be 1 volt.

That, in my experience, is not a common voltage found in model railroading.

On my layout I have a number of different power supplies with output voltages of 12, 15 and 20 VDC.

At one amp the power output of each type would be 12,000 or 15,000 or 20,000 mW.
 

IronBeltKen

Lazy Daydreamer
I read that same manual page, and, since I have several runs of 30ft of modular cable between UTP pairs in the chain, I was wondering if that meant I would have to buy ~3-4 wall warts - one for each UTP at the end of each 30ft cable. A local friend of mine assured me that just one, inserted at the optimum location, would solve the problem. And it did.
 

IronBeltKen

Lazy Daydreamer
presumably in the middle, so that no UTP is more than 15 ft from the supply?
Yes, #5 out of 8. As for being <= 15ft from supply, not so sure about that - but what matters is that all the UTPs are working now where they didn't before.
 



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