I work at the Kansas Veteran’s Home in Winfield, Kansas. Last year for Christmas I put together a town setting for the home. The layout was on a 4’X8’ sheet of plywood and styrofoam insulation. At one end I made mountains/hills by cutting the styrofoam sheeting, stacking it, and then shaping with a knife and putty knife. It looked very realistic.After the whole town is in place I scatter fack snow over every thing. For the town it’s self, I used buildings/houses, figures, ect I have collected of Windham Heights - Cobblestone Corner, purchased from the Dollar Tree Store. For lighting, I took regular Christmas tree lights, drilled holes through the plywood/styrofoam and attached each light to a small nail, and then put the building/house over it. But then came the strret lighting. Throughout the town I had about 16 street lights, 2 traffic lights, and 2 rail crossing lights All of these lights were powered by batteries. The layout was set up and operated from Monday thru Friday, for 5 weeks. We went through a lot of AA batteries. I also had an HO steam train circle the layout.
For this season my plans are to extend the layout to a 4’ X 10’ or 12’. I also plan on having 2 trains circling the layout. one will be a passenger train on level ground, with the other as a freight train, which will elevate up into the hills and then back down.
Anyway to my question - I have been looking on the net at electrical street ligts. Most can be bought 3 at a time, with wiring. How many lights can I wire together to my power pack/or packs. If anyone has other idea I am open for ideas.
If the lights are the same voltage (or a bit higher than) your pack’s voltage, then simply find the amperage of one bulb.
Read the power pack’s “volt-amp” rating and divide by the voltage. This will give the available current or amperage. Scale this down to about 80% for safety and divide by the single bulb amperage. The result is the number of bulbs that you can run in parallel.
If the bulbs are of a lower voltage than the pack you will need a more complicated ‘series/parallel’ hookup.
This is harder to explain. voltages (or needed voltages) in series add. Voltages in parallel are the same. Currents in parallel (like above) add, and and currents in series are limited by the lowest (any one if all equal) load.
For example two 6 volt bulbs in series, each drawing 0.1 amp will require 12 volts but still draw only 0.1 amp.
Two 12 volt bulbs in parallel will draw a total of 0.2 amps.
Single or parallel 6volt bulbs across a 12 volt source will get very bright for a fraction of a second. Then you replace them.
The sum of series voltages of the bulbs needs to equal or exceed the pack’s voltage rating.
The sum of parallel bulb currents needs to be less than the pack’s current rating.
I hope that this makes some sense - it’s pretty late, my brain is only in first gear.
The total amperage and voltage output of your power pack
The amperage draw and voltage rating of our light bulbs
With light bulbs, you need to keep track of the total amount of amps each bulb pulls, so that you don’t exceed the amperage output of your power pack. Likewise, you must make sure that your power pack output doesn’t exceed the total voltage of your light bulbs.
[Edit: Bob, the following explanation of current and voltage is based on wiring bulbs in parallel.]
Amps (Current)
If you have a wall transformer rated at 1.5VDC (i.e. 1.5 volts of DC power or 1.5 amps), you can power as many bulbs as you want as long as the total of their amps does NOT exceed 1.5 amps. For example, you could power (50) 30mA bulbs (mA = milliamps; 1 milliamp = 1/1000 of an amp) for a total of 1,500 milliamps (30 x 50 = 1,500). If you exceed the current draw of your source, you put undue strain on your source.
Volts
If you have a 12V bulb and your power pack is rated at 15VDC (or 15 volts of DC power), realistically you will only be able to turn the knob on your the power pack up to 80% power (80% of 15V = 12V). If you exceed that amount, you run the risk of blowing your bulb(s) and/or shortening the life of them dramatically. You can always run it with less power by adjusting the knob down.
Sooooo, it depends on your power pack and the bulbs your use. That would be true for batteries as well. It also depends on how you wire up your lights.
Wiring
As far as wiring, you have two ways to do that: either “in series” or “in parallel”. The small Christmas tree lights you used to light the layout last year are usually wired “in series”. Simply put: When lights are wired “in series”, if one bulbs burns out, the WHOLE string goes out because current has to travel through ALL the bulbs in order to return to the power so
Wow! Brain in first gear or not - I think that Karl did a splendid job of explaining voltage and currents to you. Much better than I did. As I said, I’m still learning about this stuff myself so Karl’s succinct explanation was helpful for me. Thanks, Karl! [:)]
I use a similar but not exactly the same approach for lighting buildings. For those which are flat on the layout I 1/4" drill a hole under the structure. I then take 1/4" wood dowel pins and drill a 1