Practical question

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- Den
  
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posted
20 years ago

Mon, Apr 5, 2004 6:38 PM

Group:

I've got a phone cordless phone that needs a 600mA 9V AC supply. The connector on the phone for the power is a RJ12 socket.

As I'm not too practically able (or is that I'm practically challenged?) I want to avoid soldering anything!! I can buy a wall-wart transfomer, but the low voltage cables are too 'chunky' to terminate in a RJ12 plug. So I'm planning on crimping the low voltage cables from the transformer to a small piece of CAT5 cable that terminates on a RJ12 plug.

My questions are:

a) is it safe? b) is there a better way to do it? c) [If I was a really sad character ...:) ] how would I calculate the conductor size needed to disappate the heating effect in the (relatively) small conductor of the CAT 5 cable.

Cheers

Den

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- Repeating Rifle
  
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posted
20 years ago

Mon, Apr 5, 2004 8:53 PM

in article SIhcc.23$ snipped-for-privacy@nwrddc01.gnilink.net, Den at snipped-for-privacy@nul.nul wrote on

4/5/04 11:38 AM:

You really need to change your attitude. There are great advantages to soldering, if you can do so reasonably well. Learn how. Avoid another half assed accomplishment.

Bill

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- Bill Shymanski
  
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posted
20 years ago

Wed, Apr 7, 2004 3:29 AM

challenged?) I

Of course not. You could trip over the cord, or accidentally swallow the cable, or any number of ways of hurting yourself.

Zillions. Isn't CAT5 solid wire? It will last for about a day and then go intermittent.

(An RJ12 wouldn't be my first choice for a power connector, especially on a phone...tends to get mixed up with the phone line connector. )

(relatively)

Hmm, well you could look up the heat transfer partial differential equations, calculate the Prantdl, Nusselt and Reynolds numbers, experimentally determine the thermal conductivity of the cable insulation, and the heat transfer coefficient of copper. Then you could determine the Joule heating effect in your cable due to the proposed current (not to ignore dielectric losses in the cable jacket) and from this calculate a temperature rise.

Or you could just look at it and say "Hmm, about the same size wires as every other bit of wall-wart-operated junk I have, probably OK" and not worry about it till you detected the smell of melting PVC.

Bill