120 volt AC to 12 Volt DC Convertor

If you total up the current draw of all the led strips, then add perhaps 1.5x for safety margin and future expansion that will tell you what size 12v supply you need.  Then just daisy chain the wiring of the terminal boards.  I'm not sure why you want 12 separate outputs?

Hi Randy. Just a suggestion for you to consider. I have used AC/DC compatable LED strips to light up  buildings on my layout. I then used an old AC transformer to power them. I set the transformer at a voltage that lights them up satisfactorily. The strips were pretty inexpensive, easy to stick on the underside of the roof or overhangs of the buildings to light up. Might be easier to use this type rather than buy/make a DC converter.  Wish you the best.

If you have any computer power supplies laying around you could get a breakout board that should work very well plus give you additional voltage options besides 12V

https://www.amazon.com/gp/prod...le?ie=UTF8&psc=1

John

John has the right idea, you can get tons of cheap filtered DC power from a computer power supply!  20-30 amps is about the low end of the range of 12V from even a fairly cheap PC power supply!

@JamesR posted:

Hi Randy. Just a suggestion for you to consider. I have used AC/DC compatable LED strips to light up  buildings on my layout. I then used an old AC transformer to power them. I set the transformer at a voltage that lights them up satisfactorily. The strips were pretty inexpensive, easy to stick on the underside of the roof or overhangs of the buildings to light up. Might be easier to use this type rather than buy/make a DC converter.  Wish you the best.

I am not aware of any AC compatible LED strips, and couldn't find any in doing a web search.  Could you clarify?
While any LED light strip will function on AC current, the life of the strip will be severely shortened because LEDs are damaged by the reverse current.  

There are many ways to light buildings with LEDs.  What to choose depends on how much work (ie. soldering) you want to do vs how much you want to spend.  

Lights:
Low cost:  Buy the 16' 12v LED strips, cut into sections of 3, 6, 9, etc LEDs and solder 2 wires to each strip
Higher cost:  Buy pre-wired 3 LED strips or buy screw-on or crimp-on connectors to use with cut sections of the 16' strip.  Make sure to connect the + power supply to the + pad on the light strip.  You can wire them either in a star pattern from a terminal strip or daisy chain the strips together (although that doubles the number of connections on the strips).

Power supply:
12v DC power supply.  Pick one based on total watts needed.  Most LED strips list watts per foot.  Exceed what is needed by 50% as Doug suggested
Computer ATX PC power supply with breakout board as suggested above
Or use 18vac (variable) or 14vac Accessory terminal on a hobby transformer plus 2 or more of GunrunnerJohn's LED Lighting Regulators. This has the added advantage of adjustable dimming.

Power distribution:
Low cost: Terminal strips with common connector strip
Higher cost:  MTH Terminal block (they are high amperage which is unnecessary, but they are convenient to use)
Power Distribution Hub with adjustable current (brightness)

Bob

Randy, the strips I used powered by AC transformer are these from Amazon. https://www.amazon.com/gp/prod...le?ie=UTF8&psc=1

@JamesR posted:

Randy, the strips I used powered by AC transformer are these from Amazon. https://www.amazon.com/gp/prod...le?ie=UTF8&psc=1

@JamesR

James:

Thanks for the link. Though I already have the LEDs in a long strip that require soldering, I am going to hold onto this link to use for smaller buildings. This product takes the soldering step out of the equation. What I am really looking to find via this post is a plug-into-the-wall converter that converts house current to 12-volt DC to power all of the layout buildings.

@JamesR posted:

Randy, the strips I used powered by AC transformer are these from Amazon. https://www.amazon.com/gp/prod...le?ie=UTF8&psc=1

Those are not AC strips, they're just small segments of the common 12V LED strips.  In spite of the ad copy, the actual picture tells the tale, they're plain 12V strips!  You can get sixteen feet of these from AliExpress for around $3, you're paying three times that and getting a total of a couple of feet of LED strip!

I used those on AC to light up the exterior of my Menards diner. Been doing fine for a year and half or so.

@JamesR posted:

I used those on AC to light up the exterior of my Menards diner. Been doing fine for a year and half or so.

And they will for a spell.  As long as the reverse voltage doesn't exceed the ratings of the LED's used, they work fine.  The peak voltage of 18V RMS is 50.9 volts, the negative peaks are 25.4v.  The typical max reverse voltage specification of an LED is between 5 and 7 volts.  There are three LED's in series.  Given all those facts, the LED's are experiencing some degree of out of spec reverse voltage, though the amount is mitigated by the series connection of three LED's.

I know when I used to use a plain LED and resistor for lighting TMCC stuff, the half-wave peak voltage was taking out my headlights after a spell, the problem is real.

However, as long as it works for you...

One other option not yet mentioned: I don't know about you, but I have a box full of old wall warts salvaged from defunct electronic devices in my basement (I'm an inveterate scrounger, in case you hadn't figured that out!), and a fair number are in the 9-12VDC output range. I've had good luck splicing the wall wart's output wire into the power input for LEDs (and other accessories), and if you prefer not to do splicing, matching connectors can usually be found on-line at modest cost (especially from slow-boat sources, if you can wait a few weeks!). You might have to use more than one to meet your total needs, but the price is right!

The only real caveats I'd add would be to do the arithmetic to be sure the rated power is sufficient (FWIW I agree with the suggested 50% safety margin), and be sure to check the *actual* (vs. claimed) output voltage -- there's sometimes a surprising variance between the claimed output and the actual as-measured voltage.

"I then used an old AC transformer to power them."

Me: AC is bad for LEDs

@RRDOC posted:

While any LED light strip will function on AC current, the life of the strip will be severely shortened because LEDs are damaged by the reverse current.  

GRJ: Yes, and here is the math

@gunrunnerjohn posted:

And they will for a spell.  As long as the reverse voltage doesn't exceed the ratings of the LED's used, they work fine.  The peak voltage of 18V RMS is 50.9 volts, the negative peaks are 25.4v.  The typical max reverse voltage specification of an LED is between 5 and 7 volts.  There are three LED's in series.  Given all those facts, the LED's are experiencing some degree of out of spec reverse voltage, though the amount is mitigated by the series connection of three LED's.

And there is the difference between the amateur hobbyist and the consummate professional . . .  

@Steve Tyler posted:

One other option not yet mentioned: I don't know about you, but I have a box full of old wall warts salvaged from defunct electronic devices in my basement (I'm an inveterate scrounger, in case you hadn't figured that out!), and a fair number are in the 9-12VDC output range.

You need long and flexible extension cords to use wallwarts for rolling stock like passenger cars!

@RRDOC posted:

And there is the difference between the amateur hobbyist and the consummate professional . . .  

@RRDOC,

You're on the right track but I would suggest this slight modification:

       And there is the difference between the amateur hobbyist and the most junior professional . . .

If a consummate professional, like GRJ, were required to light an LED so that it would achieve a long successful life we'd all still be using incandescent lamps in most everything.

(However, we do notice, around us, a surprising number of LEDs in products we see everywhere that die early because of design oversights including but not limited to holiday lights, retail store lighting, electronic signs, and 120 v. screw-in incandescent lamp replacements, all of which should have been designed by a minimum of a junior professional, but apparently weren't.)

Mike

It truthfully doesn't take much to achieve a long life with LED's, but it's also possible to abuse them and have a short life.

@RRDOC posted:

And there is the difference between the amateur hobbyist and the consummate professional . . .  

Awww . . . but it's just so much *fun* to spitball it! 

@gunrunnerjohn posted:

You need long and flexible extension cords to use wallwarts for rolling stock like passenger cars!

Yep:

As to powering rolling stock, it's like the old joke about electric cars -- the EV itself is cheap enough, it's just the cost of all the miles of extension cords you need to get anywhere!

@Mellow Hudson Mike posted:

If a consummate professional, like GRJ, were required to light an LED so that it would achieve a long successful life we'd all still be using incandescent lamps in most everything.

Or . . . just buy the properly engineered products like those offered by GRJ!

[You're welcome, GRJ, and my bank deposit info is all still the same! ]

@gunrunnerjohn posted:

It truthfully doesn't take much to achieve a long life with LED's, but it's also possible to abuse them and have a short life.

Yep -- once all the smoke inside escapes, they don't tend to work very well . . .

@Mellow Hudson Mike posted:

@RRDOC,

If a consummate professional, like GRJ, were required to light an LED so that it would achieve a long successful life we'd all still be using incandescent lamps in most everything.

……..

Mike

John has shown us how to do it. It is not that hard and he has even provided the electronics for sale to implement successful installations. Pat