Lighting models I: Non LED lighting

Welcome to my article on model lighting! I cover different technologies that are useful for people who want to illuminate scale models of various kinds – cars, spaceships, dollhouses, etc.

And I don’t mean shining external lights on the model, of course. I’m referring to the technology to make tiny light sources that appear to-scale with the model itself.

CHAPTER CONTENTS

The olden days – tiny incandescent bulbs

In days of yore, crusty old men and women would use flashlight/electric torch bulbs or grain of wheat/grain of rice bulbs to light their projects. Such lights are cheap, easy to wire up, fairly tolerant of power issues, available in all kinds of different sizes, emit very natural coloured white light, can be tinted different colours, and can produce a wide spread (in terms of angle) of light.

Now there's anything inherently wrong with old tech. But the drawbacks of tungsten bulbs heavily outweigh the advantages.

First, they run very hot, which can cause real temperature problems in a model, especially a plastic one. You have to make sure that the bulbs don't come in contact with surfaces that can melt or scorch, unless you run them at lower voltage than they're designed for. But if you do that then they'll output more yellow light.

Second, they have a fixed and fairly short lifespan before they literally burn out altogether. So you need to engineer ways to access and replace a dead bulb. Model railway buildings, for example, might use a bulb on the end of a straw so you can pull it down from under the table. This sort of thing is a problem for small vehicles, though.

Third, their brightness decreases and colour shifts towards the yellow as they age.  Not a massive deal with small bulbs, which tend to burn out before these shifts are noticeable, but it's an issue.

Fourth, they're technically only available in a single colour - warm white. Colour variations involve coating the bulb in varnish or using tinted lenses to alter the colour output. That's at least easy enough to do, but of course you get a drop in light output when you apply the colour.

And finally and perhaps most importantly, they eat up batteries very rapidly. Since a good part of the energy is wasted to heat, they don't produce as much light as a cool light source would. A single LED can easily draw 1/4 of the power of a single grain of wheat bulb. Low-current LEDs can use a fiftieth!

Big incandescents

This is how movie models used to be lit. Look at the huge spaceship models from the first Star Wars films - you'll see tungsten halogen bulbs. You'll also see enormous cooling systems and fans. This is partly because the models were large, and partly because film of the day required a lot of light to expose, especially with lenses stopped down for increased depth of field.

Because these lights generate tons of heat, and suck down so much power, they can't be battery powered. So they're generally impractical for hobbyist projects, putting aside issues of size. But they're not really needed anyway, since most hobbyists models don't require the massive light output that such lighting systems generate.

Neon and fluorescent tubes

As above, these were once used for movie and TV models. The massive Enterprise D model used as the first Star Trek: the Next Generation filming model, for example, contained neon tubing, much like a bar or restaurant sign. But these lights require bulky transformers and mains power, can still get warm, and are generally kind of big.

That's fine for an enormous car-sized filming miniature built on a five-figure budget. You might also put a fluorescent bulb into a skyscraper on a model railroad, so that you can get all the windows lit up. But these tubes are of no use for smaller hobbyist models.

Electroluminescent (EL) wire and panels

This is plastic wire or sheeting which glows eerily when high-frequency electricity is applied. Electroluminescent products have all kinds of cool (literally) advantages for model making. They don't produce any heat, and draw hardly any power. The material can be incredibly thin and flat (in the form of EL tape and EL panels), which is perfect for backlighting control panels and the like. Since the entire surface of the EL material glows perfectly evenly, you don't have point sources creating hotspots.

EL wire, the most common form of the stuff, is flexible and can be used to make unusually shaped objects glow. The wires also don't require a second return wire like a normal electric circuit. At least they don’t from a model builder’s point of view. The second wire is actually there internally - think the way coaxial TV cable has one wire sleeved within another - just that one of the internal electrodes is transparent or very fine. This makes them easy to install and run – you just put the EL wire somewhere, hook it up at one end, and the whole thing glows.

Those are all wins. But the drawbacks limit the technology's adoption.

Lousy colours

EL material is available in a variety of colours, but most shades aren’t useful for many types of model-making: strange greeny blues and pinks and whatnot. There are white EL products on the market, but they have a very cool blue tone when lit, and produce a generally strangely coloured glow. They certainly don’t emit anything like warm tungsten light, and are often pale pink when off, which doesn’t look great. This all may be fine for your model, depending on what it is, but it does put limits on what’s possible.

Dim light

EL material is never very bright. It’s fine for backlighting control panels viewed in dark rooms, for example, but useless for making a spotlight or a powerful rocket engine or anything easily visible in daylight. The material just emits an unearthly alien glow, and has no intensity to it. You can pump more juice into the material to boost the brightness, but at the cost of a dramatically reduced light-producing lifespan.

Extra circuitry required

You can’t simply plug EL stuff into a battery or power transformer and have it light up. You need a special electronic device called an inverter which puts out a really high frequency AC current at an extremely low amperage. This box takes up room, which is a problem in small models, and also tends to make a faint high-pitched whining or whistling noise. (higher quality inverters make such high frequency noise as to be inaudible to humans, but cost more)

Resizing is awkward

It is possible to cut EL material and solder new wires to it, but it’s very fiddly to do and takes a lot of skill and patience. Beginners should stick to using EL material with presoldered connectors. Cutting a flat EL panel down to convenient sizes and shapes is, therefore, possible but not always easy. You also have to seal up any cuts very carefully - any liquid or even moisture entering the cut area will destroy the device. Unsealed cut areas will gradually darken with time. Glue or varnish should work for that.

Brief lives

Finally, arguably its biggest drawback is that EL material has a relatively short working lifespan. As EL material is used it start to drop in light output. The time period to half brightness is in the thousands of hours, but I just don't like the idea of sealing material like that in a model that will hopefully sit around for years. (note that it doesn’t deteriorate simply with age as such - it wears with actual use)

So. Super-thin flat EL panels are perfect for tasks like backlighting your cockpit instruments or windows, or making model TV screens and monitors. The wacky colours have a certain B-movie SF utility. You can get thin EL tape material that’s flexible and easily installed all over the place. If you’ve got room for the inverter, and don’t mind the modest brightness and short lifespan of EL products, it can serve some really useful purposes. Electroluminescence is just not a great general-purpose lighting solution at this time.

Blacklight

Another approach is to put blacklight responsive paint on a model and illuminate it with blacklight - typically a fluorescent tube or LED which emits UV-A energy. White paper with optical brighteners will also glow under UV.

This can be useful, as it's quick and easy to daub spots of paint on areas which need illuminating. But it also has a weird fake glow to it compared to actual light sources. Although UV energy can't be seen by the human eye, various materials can fluoresce in strange ways. And most blacklights do emit a small amount of visible blue or purple light. They also lead to creepy blue colour casts when photographed.

LEDs are awesome

So. All these lighting methods have pretty serious drawbacks. What is the solution today? Why, LEDs, of course! Read on in the next chapter!

The next section

II: LEDs (light emitting diodes).