measuring power

[Anonymous]

I posted earlier about transformer upgrades. Since then I e-mailed MRC and asked them which solution would work:
1. CW-80 with Twin Power Box
2. MRC Pure Power AC
3. MRC-Dual Power.
I am running one train set, about 6 cars, 4 remote o gauge switches, 2 uncouplers, and I intend to add 2-3 signals and perhaps a coal dump car and lighted station.
Their answer was I had to measure the power requirements and decide myself. So ok, being a complete novice at electricity, how do I do that. Do I measure watts, volts, amps etc.? And how can a fixed voltage 14 volt terminal(as on the MRC's power so many accessories? I guess I need a primer in electricity. Please explain.[?]

[lionelsoni]

Power is the product of the voltage applied and the current drawn. So an accessory that draws, for example, 1/2 ampere at 14 volts is consuming 7 watts.

Did you see my comment on the other thread? You can get fixed-voltage accessory power pretty cheaply: Radio Shack sells a 3-ampere 12.6-volt transformer (273-1511) for $10.49. They also have a 2-ampere 25.2-volt transformer (273-1512) which you could use for two 2-ampere 12-volt circuits by grounding the center tap, for the same price.

[ben10ben]

While you're at Radio Shack getting the things Bob mentioned above, pick up their $20 clamp-on AC ammeter to measure the current draw of your trains. That's the easiest way to find out how much power you need.

Most transformer ratings are given in watts. If they're not also given in amps, you can find amps by dividing watts by volts.

[Roger Bielen]

Another source of transformers, reasonably priced, is All Electronics, WWW.allelectronics.com. They have quite a variety. I have one that is 12.6V AC, if I don't remember the Amps but it's more than I'll ever use. They no longer have the one I have in the paper catalogue but have others, i.e. 12v - 5 A for $9.50.

Check their website to see what they have.

[lionelsoni]

Their TX-125 is 12 volts at 5 amperes for $9.75.

[eZAK]

Since adding up your total wattage needed can be difficult at times and may result in an incorrect guess, Try This Rule of Thumb;

Figure on about 2 watts (or Volt Amps) per square foot of layout space.

Remember, It is always better to have more power than you need,
than it is to have not enough power.