LED stands for “Light-Emitting Diode”. Unlike regular light bulbs, LED’s are polarity sensitive. The two silvery leads attached to the clear epoxy case are called the Anode, which is electrically positive and the Cathode, which is negative. If the polarities are reversed, the LED will not light. The Anode (+) is always the longest of the two leads. The Cathode (-) is the shorter lead, also identified by a flat spot on the case next to it.

White and blue LED’s have a forward voltage rating typically of 2.5 to 3.6 volts.

TIP: Other colors of LED’s use different voltages, which is important to remember if you’ll be using LED’s of different colors. Then it gets more complicated as you have to use resistors with the LED’s of different colors. I like using just the white ones and tint the LED with a bit of transparent paint to make it the color I want.

If the rated voltage is exceeded, even for a moment, the light will burn out almost instantly or at least severely shorten the life of the LED. If the voltage is too low, the unit will not light at all. Two 1.5V alkaline batteries in series, making a 3-volt power supply, lights them up nicely. When using more than one LED, all LEDs must be wired in parallel to the power supply.

Most LED’s have a lens on the front of them to make the light project much like a flashlight. For modeling the headlights of cars or the beacons on searchlights etc., this is a really fabulous way to add life to models of police cars like Rosco’s Dodge Monaco and big rigs like the International Transtar 4300 Eagle! But if you want to have the LED throw light more evenly in different directions, sand the entire clear case with sandpaper to roughen the glossy surface and take the sheen off.

Before you begin assembling the kit, you must first mount the LED’s into place on the relevant parts. Using your 3/16” drill bit, drill holes into the parts as shown in fig 2. You’ll want a light under each of the four clear towers and on the ends of each of the three arms, totalling 7 LED’s.

TIP: To keep light from shining through the plastic from the back of the LED’s, spray paint the INSIDE surfaces of the lit up areas (except for the clear parts of course!) with silver paint before assembly. Silver does a great job of blocking light, even better than black! That’s because silver paint has microscopic flecks of metal in it that is very opaque.

Insert the LED’s from the back of the part (the inside of the model) and use a modest amount of superglue to keep it in place. Use accelerator to speed up the curing time of the glue. You must pay attention to the anode/cathode leads position relative to each other as shown in fig 3 so that you don’t get confused when you wire them together. Spread the leads apart and lay them down as shown so they don’t cross over each other or touch the opposite leads. Since the LED leads are so stiff, they won’t move once in place, so you don’t usually have to insulate them as long as you spread them apart as shown to keep them from touching each other. Bend the leads gently, deliberately and as few times as possible. If you bend them back and forth too many times, you’ll cause metal to fatigue and they’ll snap off.

Cut four lengths of each colour of wire approximately 12 inches long, strip about ¼” of insulation off each end and pair them together, one for positive, one for negative. Usually black or white is used for negative (-) while other colours, usually red or green, is used for positive (+). It doesn’t matter which colours you use as long as you remember which is which.

Using a soldering iron, soldering paste and solder, attach the wires to the cathodes and anodes as shown in fig 4.

Proper soldering technique is critical for a successful job. First, make sure your soldering iron tip is clean by scraping or sanding off any carbon or other deposits that may be on the tip. “Tin” the tip by smearing some soldering paste on and flow a little solder onto the heated tip so that it becomes bright silver. When tinned, the iron is ready to use. Keep a wet sponge handy to wipe excess solder from the tip when needed.

It’s best to smear some soldering paste onto the wires you’re soldering to help the solder flow more readily and bond to the work. You can just dip the stripped ends of the wire into the paste to coat them. The LED leads are usually pre-tinned anyway, so the solder should flow to those very readily.

When soldering, always remember to heat the WORK first, not the solder. You touch your iron to the wires you’re soldering and then apply the solder to the side opposite the iron. When heated, the solder will flow into the wire and solder properly. If you heat the solder first, the solder will melt but the work won’t accept the solder and it will bead, resulting in what’s called a “cold solder joint”. Such a joint may hold for a while, but will usually work loose over time if not immediately.

Do not heat the work excessively, or you will damage the LED’s or melt the wire’s insulation. As soon as you see the solder flow onto the wire and “blend” with it looking like liquid chrome, remove the iron and allow the work to cool. After about twenty seconds of cooling, tug LIGHTLY on the wires to make sure they don’t come loose from the LED’s.

Remember, the iron is very hot and will melt plastic in an instant, so keep it well away from your model’s plastic parts! Keep your work table uncluttered (in other words, not like mine!). Have handy only the parts you are working on at that moment to avoid accidents.

Once you have the wires soldered to the four lighting points (the two on each of the three arms and the one in the main command section), test them by temporarily wiring each of the four assemblies to the battery box, again paying attention to polarity. Put the batteries in and see if the lights work as in fig 5. If they do, great! You can now glue on the other halves of the station sections as in fig 6. Make sure you don’t allow the wires to fall back inside these assemblies! If the lights don’t work, check your polarities. If they still don’t work, you may have a bad LED or the batteries may not be fresh. Remember you need TWO 1.5v alkaline batteries in series making 3 volts in order for the lights to work.

After testing, remove the batteries from the battery box immediately so that if the leads from the battery box accidentally touch each other they won’t cause a short circuit.

When you’re sure all the lights work and are hooked up correctly you can finish the model. If your wires are heavy, they may not all fit down through the stand so you may have to attach the wiring at the station’s hub and run just two or four wires (including the two from the command tower) down through to the bottom of the model. Make sure you clear holes to allow the wires to travel all the way down to the display stand. Allow a good length of wire to exit the bottom of the model so you have lots to work from when you attach the stand and wire up the switch and batteries. Have a look at figs 7 through 9 to see how I worked with the example I built for this article. Work however you feel comfortable, but make sure you carefully think through all you need to do and plan ahead before applying glue. It’s a good idea to practice assembling the model entirely with tape so you can see where everything needs to go and the sequence you can use. Then test all the lights again. When you’re satisfied, glue it all together and finish as desired.

TIPS: For the clear towers, if you don’t want them to be fully illuminated but want the correct windows only to light, spray the OUTSIDE of them with white, to aid in light diffusion inside, then silver to block the light, then back up with the hull color. You can mask off the areas you want light to shine through, or, just scrape off the paint from the “windows” when dry. Do not allow any paint to get into the insides of the cones!

To help diffuse the light further, you can spray the INSIDE of the cones with clear dull coat or other plastic compatible matte varnish. You can also line the inside of the cones with translucent paper.

Save those clear cones as the very last thing to put onto the model, even after you have the stand mounted.

In order to light the model you’ll need to have a place to put the switch and battery pack. There are hundreds of different types of switches to be found at electronics supply stores, on the internet or you can rob one from an old broken radio or TV set. Just make sure it’s compatible with your needs and looks good when mounted to the base. Just a simple On-off switch is all you need. The switch I used is a friction fit, so you just drill the appropriately sized hole into the base and push the switch into place with no screws or glue needed.

Mounting the battery box is a bit different and presents a few problems. Most have screw holes to mount them but in this case we’re mounting it to something that has a wall thickness inadequate for screws, so we have to glue it in place. Another problem is that when you fit the box the only surfaces that touch are the four outer corners because we’re mounting it to the inside of a spherical cap made of ABS (Acrylonitrile Butadiene Styrene). Yet another problem is that the battery box (depending on the kind you get) is likely made from polypropylene, which is flexible and soft but there is no glue (that I know of) that adequately bond to it and also to ABS. So how do we overcome all these obstacles?

Begin by using the tip of your hobby knife to score the plastic parts as shown in fig 10. Press firmly, but not hard enough to cut the surfaces completely. You want to score a lot of lines in every direction to severely roughen the surface and give our glue something to grab onto.

I used hot-melt glue for my example (fig 11) because it’s fast. But that can be tricky. If you get the ABS plastic base too hot it will warp and distort, so, I recommend using epoxy, such as five-minute epoxy. Superglue won’t work very well for this because it’s too brittle. Some people have told me that silicone caulking can also work for this kind of thing but I don’t want to hold the parts for 24 hours or more while it cures. Some also say contact cement can work too, but I’ve not tested it in this type of application. So, follow the directions on the Epoxy package, mix up a batch of epoxy and apply a few gobs of it liberally onto the bottom four corners of the box, stick it in place and hold it there ‘til the epoxy cures. More epoxy can be plastered around the sides too, jam it in anywhere you can get it, but be careful not to impede the springs or other metal contacts inside the box.

When the switch and battery box are in place, just feed the wires from the model down the stand tube that you have replaced the kit-included rod with, and into the base underneath. You’ll have to drill a hole in the bottom of the stand support receptacle for the wires to come through. Bring the wires through, put the model in place and hook the wires to the battery box while re-routing one of the wires through the switch. Remember the polarity! Solder the wires in place after testing. Then, insulate the soldered wire ends with electrical tape or heat shrink tubing (fig 12), then tuck the wires away and secure them with superglue, or epoxy, or tape.

And you’re done!

Fig 13 shows the model as finished without the lights turned on.

Install a couple of AAA alkaline batteries into the battery box, put the model on your shelf or desk, switch it on and enjoy the work you’ve accomplished, which should be something like that as shown in fig 14! (Note, the model’s lights won’t show up quite as well in a brightly lit room!)

Now that you’ve successfully completed this relatively simple job of lighting up the K-7 Space Station, go for a more challenging subject next… How about lighting up Round 2’s fantastic 1/350th scale Starship Enterprise “A”? Or, you could try putting lights on all kinds of models shown here on Round 2’s web site. Have a look around! There’s something for everyone here!