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How Many Lights Can Be Run Off A Transformer?
Reynold asks readers for advice:
“My N scale layout has 78 building yard lights not including the signals which I have spread over 4 transformers. If possible I would like to have them set up to all operate off just one power supply specifically for lighting. Is this hard to do? What would I need as a minimum transformer power output? I am hoping someone can shed some light on the problem – sorry about the bad pun!!!”
5 Responses to How Many Lights Can Be Run Off A Transformer?
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Hi I have an N scale layout which I run 124 lights 12 volt led of various types ( street and yard) and 42 for various buildings again 12 volt led . I use a W. E. P. PS3050 Dc power supply which I bought of eBay its adjustable from 0-30 volts and 0-5 Amps. It was about $70 handles the layout easily with plenty of power left so I can add more lights if need be. Hope this helps Graeme.
Hi Reynold
It depends on whether you are using LED’s or incandescence lamps the later will dray more current so you will need to work out what each lamp uses and by adding up the total current draw and having a transformer to handle this I presume you will be running 12 volts Dc on your lighting circuits. So if you intend to rectify the AC output of the transformer a lesser voltage transformer will do just remember that AC rectified to DC is 1.4 times the voltage of AC so the rectifier will also need to handle the same current.
You need to tell us first:
Are your lights bulb or LED ? (Bulbs can run on DC or AC, but LEDs need DC.)
What voltage do they work on ?
If bulbs, what current does each bulb take ?
To expand slightly on Kevin’s post:
If your lights are incandescsent bulbs, (normally 12 to 16V if sold for model railroads), thay can run on AC directly from a suitable transformer. Assuming they are all the same voltage bulbs in parallel, your transformer must have a current output capability at least equal to the total current taken by the bulbs.
For example, 80 lights, each taking 50mA would require 80 x 50mA = 4 Amps (minimum) transformer output rating.
As already mentioned, LEDs use much less power, but must be run from a PSU (Power Supply Unit) that has a DC output with voltage control.(to avoid frying them).
Small LEDs take about 25mA maximum (and HO model railroad lights probably much less).
So (if each LED has its own resistor to limit the current it takes) 80 x 25mA = 2 Amps DC PSU (minimum) output rating.
Our club layout is 30×60 with all scenes in the middle of a city–LED lights on everything that doesn’t move. Most quality 12 volt DC transformers are 2,5 watts with/or without a meter to control the voltage and an on-off switch.Formulas aside, we have not hit the wall as yet and we are beyond 80 and it never even breaks a sweat.
When using LED’s I limit there current to about 10mA with a vansoft.co.za download page. It has an electronic calculator that can be used to calculate the resistor values as needed.