Questions on wiring structures for lights (part 2)

Hi Jarrell,

Here's what I can tell you about resistors:

I always use a resistor on accessories to run the bulbs at less than their rated voltage.  I find that it makes the light brightness more realistic; more importantly, it makes the bulbs last many times longer.  When I build a structure I usually make no provisions to replace bulbs, so I need for them to last thousands of hours.  In terms of selecting resistors, I'm not very scientific.  I have a power pack on my work bench and I have an assortment of resistors up to 220 ohm; I just combine resistors until the bulb looks right.  I usually start with a 220 ohm resistor in series with the bulb(s), then I add resistors in parallel with the first resistor until I'm happy.  Then I solder it all together and install it in the structure, resistors and all.

I've had a little bit of electronics training and I know how to use Ohm's Law to select the "right" resistor, but I find that there is enough variability in lamps that trial and error really is the most effective.

I posted a picture of my latest structure project with the wiring visible.  It's on the most recent WPF.

For what it's worth, for structures I find that multiple dim bulbs makes the lighting look more realistic than one brighter bulb.  I think it also looks best if the bulbs are near ceiling height inside the structure.

One last thing - if you buy bulbs on eBay or at train shows you can save money by buying bunches of colored bulbs.  Apparently the demand for colored bulbs is fairly low, so the prices are also lower than clear bulb prices.  The color comes off by giving them a bath in acetone.  Paint stripper works too, but I find it to be more unpleasant than acetone.

jacon12

Currently, I'm using Minatronics lamps rated at 1.5V 40mA (these came with resistors to wire in appropriately) but I also have a few Model power lamps rated @ 12-16V 30mA that I'd like to use.

1- Does it make any difference what voltage/amperage the lamps are, i.e. can they be mixed or do they have to be wired separately to their own power pak?

Jarrell, you should keep like-voltages on the same bus.  You can't power 1.5V and 12V bulbs together unless you use resistors.  1.5V bulbs will blow @ 12V and the 12Vs won't even power up at 1.5V.  You can mix and match amperages though.  The one thing you have to be concerned about with that is that the accumulative sum does NOT exceed the amperage rating of your power source.

2- When do you know that a resistor should be used?  Is that only when you're wiring the lamps up to AC?  The ModelPower lamps didn't include them in the package.

Personally, I wouldn't even mess with resistors.  I would just use the bulbs with the proper voltage.

3- What connections on the power pak, AC or variable DC, does the main bus connect to and what difference does it make?

Jarrell, here's where you have a choice.  You can 1) match the lights to the AC terminal for a constant intensity, or 2) use the DC terminals so that you can adjust or dim the lighting with your power pack; thereby saving on the life (hrs rating) of the bulbs.

Personally, I like option 2.  I like to dial down my interior lighting to ~50-60% of the incandescent bulbs rating.  It's still plenty of light but gives a nice, warm glow to a structure or building's interior.

Here's an example of 12V bulbs powered @ 8V:

I used Miniatronics 1.7mm 12V - 40mA incandescents (5,000 hrs) to light both my freight depot's interior and exterior.  They were a compromise to the 1.2mm 1.5V, which are more prototypically correct but only rated at 1,000 hrs.

4- On a 'mid sized' layout, that will include about 10-15 lamps of the above type, should I have a second power pack and a second main bus?

Only if you plan on using different bulb voltages for both interior and exterior lighting.  As I mentioned in the other thread, I would separate the two.  That way you can adjust the intensity inside your buildings and structures without effecting those lights that would "normally" be a constant intensity.  However, I would still hook them to the DC terminals so that you can lower the voltage and extend the life of the bulbs.

Jarrell, hope that helps...

Tom

 Jarrell, Tom pretty much took my thunder on this question. What I do is use three different transformers using the track side power. In inter mix the lights all through out the town. That way not all the buildings have there lights at the same brightness.  As stated it will make the bulbs last a lot longer. I am using a lot of the model power lights like you and have not replaced one for 2 years now.

 Couple of thing you can do to make the lights look better is glue them to the underside of the roof if there is no floor. Use a straw painted the color of the inside of the building to hide the lights wires. Added walls or floors to two story building's to the inside that will block the light out say the front, so only the back lights up or second floor is lite.

              Cuda Ken 

I like to use the variable DC outputs for 12-14V bulbs, I find usually about 50% power looks right. I use an old MRC Tech II dualpack, using one for interior lights and one for exterior lights like streetlights. If you hook them up to the straight 12V DC the bulbs will be (IMHO) unrealistically bright - and as noted will burn out a lot quicker.

With 1.5 volt bulbs I think it's basically "all or nothing", either they're on full or they're off, but I might be wrong?? I tried 1.5V bulbs but didn't really care for them except when connected to battery power like inside of passenger cars or cabooses.

Stix,

You can dim 1.5V incandescents just like any other higher voltage bulb.  You just don't have as wide a margin of variability.  I'm guessing that's probably what you were referring to by your phrase "all or nothing".

The one thing that I have found with the smaller diameter 1.5V incandescents is inconsistencies with how they shed light.  Maybe I got a bad batch but about half of my 10-pak of Miniatronics 1.2mm bulbs emitted a "concentrated" or "skewed" light, while the rest were more diffuse - which is what I prefer.

My guess is that the bottom part of the glass bulb surrounding the filament tends to be thicker in the smaller OD bulbs, which acts as a magnifier.  This is another reason I decided to go with the larger 1.7mm bulbs.