Low voltage wiring question

[John-NYBW]

My weak suit in model railroading is definitely in the electrical area. I am about to begin construction of a 4x8 snow covered Christmas village layout and have alread acquired many of the snow covered structures from a variety of sources. Most of them have internal lighting and a few use battery power to light the structure. Since I plan to permanently mount the structures on the layout, having to replace the AAA batteries is going to be a hassle. In addition, placing them so the on/off switch is easily reachable is going to limit where they can be placed. 

I'm wondering if I could use the same low voltage current I use for LED lighting and wire it to the battery terminals. Is that a feasible option for eliminating battery power? If that is an option, does polarity matter?

[hon30critter]

John-NYBW

I'm wondering if I could use the same low voltage current I use for LED lighting and wire it to the battery terminals.

Hi John,

This is the sort of question that can best be answered with a 'maybe'.

The first thing you will have to do is determine what the voltage is for each of the structures. If you are lucky they will all be the same voltage, in which case you could use a single wall wart power supply (or a couple of larger batteries) to power everything. If each of the structures uses two regular 1.5v batteries (usually AA) then all the lights operate on 3 volts. You can get a 3 volt 1 amp power supply for peanuts.

If any of the structures use a single battery, or three batteries or more (unlikely) then their voltage will be lower (1.5v for a single battery) or higher (3 x 1.5v batteries = 4.5 volts). That will complicate the power supply, but if you simply replace the 4.5v light with a 3v LED, the problem will be solved. There is no need to remove the old light(s). Just disconnect them and put a new LED into the structure.

Note that you want to wire the structures in parallel, not series. In other words, you don't want to connect all of the lights in a string where one light feeds the next light. This is an ideal situation for setting up a lighting bus just as you would when wiring track.

Feel free to ask more questions.

Cheers!!

Dave

[gmpullman]

Buck-Boost regulators are a good way to lower DC voltage from the common 12VDC wall warts, too.

https://a.co/d/8oLrRzL

Some have built-in voltage indicators, too but you can simply measure the output with a VOM as well.

https://a.co/d/g3L29pu

There is a trim pot on these that allow you do 'dial-in' whatever output voltage you need. I use them for my Miller 'neon' signs that are provided with a 3 AAA battery holder but I convert them all to my lighting buss.

Yes, polarity matters but most wall warts have a dashed line on one side of the circuit but it is best to also check these with your meter, too. If the meter is giving you a negative voltage reading you have the polarity reversed. If you use a 1 amp wall wart you should be good for about 300 LEDs.

Good Luck, Ed

 

[John-NYBW]

The structures in question use a pair of AAA batteries. I had thought of just putting LEDs in them but I though since they already have the LEDs, why not just wire the battery terminals. 

Many of the structures I have acquired were on ebay and come with a single incandescent bulb, a little smaller than a Christmas tree light. They are powered with an ordinary wall plug with a dimmer switch and if I used them as is, I'd need several power strips. I'm probably going to replace those with LEDs so it would not be too much trouble to light the battery powered structures the same way.

[MisterBeasley]

The first phase of my layout was built rather haphazardly, and I ended up with a lot of wall-warts to provide the collection of voltages.  After that, I bought cheap 12 VDC power supplies online and simply added resistors to the circuits to get what I wanted.  The power supplies are individually fused because they don’t have circuit breakers.

This works fine for all my incandescent structure lighting, for  which I use 16 volt bulbs and find the 12 volt supplies just perfect.  I have several Miller Engineering lights as well.  The single supply only takes one outlet on a terminal strip, and I run a line to a toggle on the control panel so I can shut the lights off while still running the trains.