LED Building lighting and HO DC Transformer

Yep, the only issue is making sure you don't crank the voltage up too high.  Use the DC output, set it at 11-12 volts measured, and you can light up lots of buildings on the layout.  The LED strips cut with three LED's and a resistor sections, each section uses a maximum of 20ma.  The whole strip of 300 LED's is rated at 2 amps.  Let's say the HO power supply DC output is good for 300ma, that will do 15 groups of three LED's on the strips, or 45 total LED's.

Thanks John.  So each strip needs a resistor? What size?  If I use a barrier strip to feed several buildings from one set of power leads can I use an appropriate size resistor on the line side of the barrier strip or do I need individual resistors on each load coming from the barrier strip?

The strips have the resistor built in.  Just be sure to cut where the cut mark is, as John said - usually every 3 leds. And keep your voltage around 11v-12v.

You can use this for the lighting but DO NOT try to set the voltage and leave it thinking it will stay. These power packs are non regulated if you turn the AC power off and then turn the power back on they can spike to full voltage. The result is all your LED’S will go really bright never to light again. Don’t ask me how I know this….

 To use it as is you will need to have the DC turned off when applying the AC power and then bring up the DC power up to your setting. Forget one time and you may be replacing all your LED’S.

 To use it as a set and forget you should add a 12vdc regulator between the power pack and your led’s.

 For this reason I just went ahead and purchased a regulated 10A 12 VDC supply off the Bay for $16 with free shipping. With 10amps of power I don’t need to keep track of the number of led’s I use.

Thanks guys.  I read John response too quickly and didn't see "cut" so I thought John was saying use three LEDs and a resistor not realizing the resistors were included in the strip.

I would also recommend a regulated 12 vdc power supply for the LED strips. Many of the LED reel suppliers also offer power supplies.

I like the idea of a regulated supply, but if you want to use the HO supply, one trick is to connect an incandescent bulb across the output along with the LED strips.  This will limit the spike that happens on power on.

OTOH, the regulated supply is clearly a better idea, and they can be dirt cheap.  eBay #: 152337854739 is a 1.5A supply  for $4.89 shipped that will do several hundred of the LED's on the strips.  It's a US seller as well, so you'll get it pretty quickly.

John:

I just purchased the power supply below. I want to power three independent row of SPST Atlas O switches (about 12 per row). I asked about circuit breaker in case of a short (it has a 'fast' breaker) but did not think about voltage spike on power on. What is your opinion? should I install the light bulb in series with the Atlas switches on my control board?

http://www.12voltpowersupplies.us/

30A   I'd certainly have breakers or fuses on any wiring coming away from this supply!  30A is enough to start fires with a short.

Model Structures posted:

John:

I just purchased the power supply below. I want to power three independent row of SPST Atlas O switches (about 12 per row). I asked about circuit breaker in case of a short (it has a 'fast' breaker) but did not think about voltage spike on power on. What is your opinion? should I install the light bulb in series with the Atlas switches on my control board?

http://www.12voltpowersupplies.us/

Your power supply is heavy enough for 100W HAM RADIOS.  Now is it regulated?  Do you have an instruction sheet?

John thanks for the heads up on the power supply.

John:

It is 10 amps per output - three outputs total. I can install fuses if necessary. What do you think?

Joe

I'd have fuses for 10 amp channels as well in any case.  If you're powering accessories from this, I doubt you're going to use #12 wire all around.

I'm pretty sure those connections are simply paralleled, you can get up to 30 watts from any of them.  Nothing in the description, the instruction sheet, or the picture suggests there are three independent channels. 

MegaWatt S-350-12 Power Supply Evaluation

MW S-320-12 Instruction Sheet

John:

Thank you. I will send am email to Marle asking about the max output for each if the three +V/-V pairs and report what I find out.

Joe

Just check the three power outputs with an ohmmeter, I'll bet you find they're all connected together, just as the grounds are.

One other thing. That small Tyco power pack isn't the best choice among HO packs for this application. The variable speed control consists of a very small arc range -- something slightly less than 180 degrees at something like a 1-inch radius. Even if you are careful enough to set it at 12 volts, one small bump to the right could quickly push the voltage to its maximum 18-volt output.

John:

You are right - according to John Marles:

Thanks Jim, I have a couple on hand and just thought it could be an easy answer to powering the lights.  I didn't plan on the Ron Popeil "set it and forget it" operation but I'll have to pay attention to your point if I stick with my original plan.  GRJ provided an inexpensive alternative so I may go that route.

Model Structures posted:

John:

You are right - according to John Marles

In this case, it was no big surprise.  If there were actually three independent channels, two things would have been true.

#1, it would have cost more.

#2, there would have been components obvious to support the independent channels.