Wiring Interior Light Bulbs

[Benjamin Maggi]

On my N scale layout, I prepared the structures for interior lights. (Painted interior black, left floors off, chiseled a whole in foam board for bulbs, drilled holed for wiring, etc...) and plan on using Brawa #3400 Bulbs. I like them because they have a screw in base and look large enough to cast enough light. They are rated at 14-19 volts. I plan to install each one seperately and control each house with a SPST switch. Panel is already completed. Power will be provided by a Bachmann lefty-center off-righty cheap train set power pack. Was going to use the DC output and regulate it by the lever to control the output, like a built in resistor or dimmer switch. I only plan to use 4 or 5 bulbs (it is a tiny layout), but I have some questions.

1. Would it be better to install a resistor in line with each bulb and then put the power pack on full, or rather run them directly (not daisy chain, but through each SPST switch) and control output with the power pack setting?
I like these bulbs because they are easy to replace if they burn out, but I still want to limit current for each one to prolong life. That is why I ask).

2. If I use a resistor for each one, assuming that I will be running 4 or 5 bulbs total off a cheap bachmann power pack what value should the resistor be? Since all 5 will be drawing, they might in fact limit each other. I will generally have them all on at once, but some times not.

3. Is it okay to run the power off of the DC output, or must I use the AC?

4. If anyone has used these bulbs before, what shoudl I expect for heat output. The houses have windows, but not too much ventilation. I don't expect to have the lights on for long periods of time. The lights will be sunk INTO the foundation of the house and the light will shine UP into the house. So, the bulb will be an inch below the building.

Thanks in advance for all the help you guys can provide!

Ben

[MisterBeasley]

I would run them directly off the DC, since it's easily varied. All the resistors will do is lower the voltage to the light, but the power pack will already do that. DC will work fine.

Your design will probably give enough ventilation, but more never hurts. If the windows are all glazed with plastic, then you really won't get much airflow. If they are open to the air, then there should be no problem. Excess heat, though, will probably shorten the life of the bulbs.

Have you considered using LED's instead? Since you are already planning on putting the bulb down low, you could shine the LED straight up and put a white surface on the inside roof. LEDs are very directional, but by bouncing the light off the ceiling you can get a lot of reflected light in the building. LEDs do need resistors, typically 440 to 1K ohms. LEDs have a very long lifetime, and they throw very little heat so ventilation is less of a problem.

[Anonymous]

This is sort of a pet peeve of mine, so please don't take it personally, but how many houses have you seen that have lights on the floor in the middle of the room?

I've seen very few instances where it looks good. I've seen plenty more where it looked downright silly. If you want it to look right, take the extra time to hang lights from the ceilings, build view blocks so all the windows aren't lighted, etc.

I also second Beasely's suggestion to use LEDs - especially the Surface Mount ones.

Again, no offense intended. It's your layout, but you may be disappointed in your methodology.

Mike Tennent

[emdgp92]

Most of my N scale buildings will be lighted as well. I built my own light fixtures from Model Power sockets (the plain ones, without the yellow bases) and some aluminum tubing. They look a bit like modern traffic lights--the upright post is inserted through a hole drilled in the base, and the arm runs out from the top. It's a bit crude, but once it's painted black to match the inside of my buildings, it's nearly invisible.

Before you start putting lights in buildings, the inside must be painted black and any light leaks must be sealed. Bulb heat must be taken into account as well. Foil or scraps of metal can be used to protect against heat damage to roofs and walls.

[Soo Line fan]

Your pack does not have a high enough voltage rating to cause a problem. Problems occur with 12v bulbs used with 14v or higher power supplies. Wiring them in parallel (direct) is the way to go. As has already been explained, your pack is a large adjustable resistor so adding any is not necessary. Use the adjustable DC voltage, not because it is DC but because it is adjustable. I have around 25-lighted buildings on my layout and I also use screw in bulbs, 12-14v. They are mounted high and shine down. I buy the screw bases with out any wiring attached, that way I add my own in what ever length I need. My power supply is an old Lionel SW transformer; I limit the voltage to 12v AC with one of the throttles. I cannot remember the last time I changed a bulb. They are on a quite a bit. Autos have been using bulbs inside dashboard clusters for ages, many in smaller confines than your buildings. The difference is the base. If a screw in base were used in a car, road vibrations would cause them to loosen. The thermal extremes in a dash exceed anything on your layout. You will not have a problem with heat as long as you avoid direct contact with plastic.

Jim

[Anonymous]

I concur that you should mount your bulbs higher. Also, if you are sinking them into the foam (did I understand that correctly) then you may have a possible fire hazard. Seems kind of unlikely given the small size of the bulb, but not something to take chances with - you want plenty of clearance between an incandescent bulb and any foam. On the power pack, just make sure its not injecting pulse, which is fine for motors but can overstress a bulb.

[Medina1128]

I plan to attach my bulbs to the ceiling with the wires run in the corner of the walls. You can get a small variable resistor at Radio Shack. Run your output to the resistor, then on the dstribution block that you wire all of your bulbs to. This way, the bulbs are in parallel, and you can turn the voltage down to dim the lights.
Before you install your buildings on the layout, create a light block, using common black construction paper. This will allow the light to be seen in only a couple of rooms or less. If your source voltage is less than the operating voltage of the bulbs, the bulbs won't be as bright. Interior lighting should be a little subdued for a more realistic appearance.