Powering LEDs

[JST]

Hi,

I am getting round to fitting lights (all LED) on the layout and am looking for a power supply. It is a reasonably large layout and will end up with maybe 200 plus LEDs. The average 1 amp transformer will not hack it so I am looking for something else. I have one of these powering LED lighting in my garden (the transformer is indoors!) and am wondering if it would be OK to use one on my layout.

 

https://www.amazon.co.uk/Redrex-Universal-Regulated-Switching-Transformer/dp/B01MZ24ZUP/ref=pd_vtph_lp_t_3?_encoding=UTF8&pd_rd_i=B01MZ24ZUP&pd_rd_r=f6e1e0e0-86b9-11e8-a2e6-c55a064349a9&pd_rd_w=X9gmY&pd_rd_wg=nbAYw&pf_rd_i=desktop-dp-sims&pf_rd_m=A3P5ROKL5A1OLE&pf_rd_p=3950386175001893296&pf_rd_r=VQP1WEGB5BM0WV3KATX9&pf_rd_s=desktop-dp-sims&pf_rd_t=40701&psc=1&refRID=VQP1WEGB5BM0WV3KATX9

 

If not, anyone got any suggestions?

 

Cheers

[Ian Morgan]

Are you talking about LEDs inside model buildings, road signs, traffic lights, etc, or do you want to illuminate the layout?

 

Modern miniature individual LEDs will produce light with less than 5mA of current flowing. If you have a suitable dropper resistor for each LED, so they are all in parallel, you are only looking at a total of 1A to drive them all. If you use a 12VDC power supply, you could put 4 or 5 LEDs in series with a single resistor, so they would share the same current. The total current draw for all 20 would then be only 0,2 or 0.24A.

 

You only need 10A power supplies if you are lighting a layout with high power LED clusters or reels. Check the specifications for the lighting you want to use.

[JST]

Thanks Ian. Yes I was thinking of buildings, traffic lights etc. However, I suppose I could do with some additional ambiance lighting over the layout so maybe 10 amps would be useful. I also like overkill!

[AndyID]

Are you talking about LEDs inside model buildings, road signs, traffic lights, etc, or do you want to illuminate the layout?

 

Modern miniature individual LEDs will produce light with less than 5mA of current flowing. If you have a suitable dropper resistor for each LED, so they are all in parallel, you are only looking at a total of 1A to drive them all. If you use a 12VDC power supply, you could put 4 or 5 LEDs in series with a single resistor, so they would share the same current. The total current draw for all 20 would then be only 0,2 or 0.24A.

 

You only need 10A power supplies if you are lighting a layout with high power LED clusters or reels. Check the specifications for the lighting you want to use.

 

And it's probably a lot safer to use several lower current supplies rather than one big one. 10 amps through a thin wire or bad connection can produce enough heat to start a fire.

[DCB]

LEDs have moved on recently, Clear LEDs used to require at least 3 volts but the Christmas lights / table lights I had from Poundland recently are clear LEDs and operate from 2 X AAA batteries. I think there are 12 of them, ready wired, with switch and battery holder. I just fitted them.  

 

Going old school if you use 12 volts and resistors to fine tune the brightness of the LEDs as you might need 12 volts 5 amps for 100 LEDs but for lighting buildings where brightness is not crucial  [EDIT] [and you don't need clear LEDs] a 2.4 volt supply should be fine,    2.4 volts 1 amp should run 100 LEDS.   For traffic lights and railway signals you will probably need 3.6 volts to allow different resistors for different colours as reds always seem to glow more brightly than greens for the same Vf but I would separate the building light circuit from the traffic lights and signals circuit

 

Edit. My AAA batteries are actually 1.6 volt, against a nominal 1.2 so the figures are 3.2 volts for these modern high efficiency clear LEDs so they might not light on 2.4 volts.   The Poundland LEDs are actually a string of 20. I just drilled a load of holes in a bit of wood , poked the LEDs though and hung them in the Rabbit Hutch to provide moonlight on dark dry nights. 10 minute job.   Rabbit Hutch is the removable cover over an outside terminus in 00 The next job is to light the station building which will need yellow LEDs, Maybe do it tonight.   I might use batteries or may use a 3.2 volt supply.  

 

The Poundland LEDs could be of use to folks with dark dingy hidden sidings?

Edited July 14, 2018 by DavidCBroad

[Crosland]

Going old school if you use 12 volts and resistors to fine tune the brightness of the LEDs as you might need 12 volts 5 amps for 100 LEDs

That's 50mA per LED. You are out by almost an order of magnitude on the current or number of LEDs it will run. A 1 A supply will be more than enough.

 

2.4 volts 1 amp should run 100 LEDS.

1 A will run 100 LEDs, whether the voltage is 2.4, 12, or 100 V if suitable resistors are used.