Using LEDs in buildings

LEDs are now the standard method of adding lights all over the layout, including buildings.

They are small, cheap, and don't get hot, making them ideal in modelling. There are a few things to consider when using them within a building. Here is my list of items to keep in mind:

  1. Make sure the light cannot leak out through joints in the building or even directly through the walls or roof. Nothing looks more unrealistic than a glowing house. You may have to add a paper mask inside, or between the light and the roof and walls. Test in a dark room.
  2. Don't make the light too bright. Modern LEDs can be very bright. LEDs are usually run at about 20mA and this may be way too bright for a building. You may want to design your electrical circuits so that the LEDs run between 5mA and 12mA.

    I usually recommend a 12V DC bus to power all your lighting. This lets you power up to four white LEDs in series in each circuit at around 10mA with the following resistor values:

    1 LED, use a 1000 Ohm resistor
    2 LEDs, use a 680 Ohm resistor
    3 LEDs, use a 390 Ohm resistor
    4 LEDs, use a 120 Ohm resistor
    See this page for all the details on the electrical side of things.

    One can also place a pulse width dimmer on the 12V bus so that you can dim all the lights at once, but it will act on all of them which is not very useful. If you want to vary the brightness one can also control the maximum brightness of individual LEDs by running them from a RemoteSign ESP at 3.3V and a 120 Ohm resistor. Once the building is complete, you can then experiment with the brightness to determine the best value.
  3. Place the light where it would normally be inside the building. Typically, lights are placed overhead in each room, so placing them on the underside of the ceiling is a much better choice than placing it on the floor. When the lights are placed high up, the light coming out of the windows falls down to the ground in a natural way and adds much more realism.

  4. Pay some attention to the color of the light. Use cool white LEDs for rooms that would likely be lit using fluorescent lighting. Use warm white for spaces that are likely lit using incandescent lighting, but be aware that many LEDs sold as 'warm white' are more like yellow. I sometimes add a bit of yellow acrylic paint to a cool white LED to give it a warmer color.
  5. Take care with lighting effects. These days there are numerous products that will create special lighting effects such as the flickering start of a fluorescent light, welding, fades, etc. (For example RemoteSign ESP). If you are using startup sequences, take care not to connect all the lights in the building to the same output that creates the effect. I once saw a video of a train station where the lights of every platform all flickered into life in perfect unison, which spoiled the whole effect of having some lights flicker on startup.
  6. Some lights are on all the time. Don't feel it is necessary to be able to switch every light on and off, or have them going on and off at random times. Places such as station platforms are typically lit from dusk to dawn, so a single switched circuit can handle all those lights together. Other spaces such as station buildings and offices are lit all day, so those can all be powered by a circuit that does not have independent switching. Lighting that is not too bright can also be unnoticeable during the day, and can simpley be left on all the time. See farm lighting experiment.
  7. Not all rooms are lit at the same time. Depending on the type of building, you may want to mask some windows off to simulate rooms that have their lights off. Consider which windows would be part of a single room though, you don't want to make it look like each room only has one window.
  8. If the windows of your building are clear, illuminating the room will enable the interior to be seen. This then suggests you should also add appropriate interior details.

    If you don't want to add interior details, then consider adding curtains or some window decoration so that the light shines through, but we can't see in.

  9. Think of where the wires will run. You don't want thick wires to create shadows or large visible 'pipes' if one can see through the windows. Wires can be collected into small tubes (E.g. a straw) or carefully glued into a corner of the room. You can now buy the small surface mount LEDs already soldered onto 'Litzen' wires which are thin as hair.
  10. It is best to include the LEDs when you build the kit. Access is better, and one can drill holes for wiring, add masks, etc.