Articles:
Gremlins in the Garage!

Let There Be Light
by Donal V. Buckley
The addition of light to a model can go a long way to customising a kit in a way that is unique and doesnt require masterclass painting or sculpting skills. With some basic information, care and patience, ( of which we all have plenty, right? ) and minimal cost, you can light any suitable kit. Granted in the kit area you may not find a huge amount of use but some types, robots and spacecraft lend themselves to enhancement by lighting.

Before starting to light any model, there are some basic questions that must be answered.

  1. What are the areas to be lit?
  2. What colour is required for the desired effect?
  3. What will be the light source?
  4. What will the power source be?

Question one is obvious but probably no less than not starting to paint until youve decided the desired effect. Question two should be decided before continuing. There are many differences in the set-up between a coloured light source and a white light source. Question three is important for a couple of reasons; depending on the colour required, you may have problems with heat dissipation, or hiding the light source. If its white you have to use lamps with different heat output and power setup whereas if its coloured it may require more circuitry. Question four could be the determining factor; battery, DC or AC. This will be answered by considering the light source you have in mind, where youll have the model and will it be permanent or movable?

Tools

If you intend regularly making electronic lighting sets, there are certain tools required.
  1. Soldering Iron, ( electric or Gas portable )
  2. Good pliers.
  3. Good electronics type wire snips
  4. Multimeter
  5. Resin-cored solder
  6. De-soldering tool or Solder Wick.

To explain each of these

The soldering iron is used to solder wire / components together, components into circuits etc. My own choice is electric iron. However Butane powered portable irons are also very useful. Word of caution when buying either, make sure the iron has an easily changed tip and that you can find replacement tips easily. Weller Irons and tips are the most widely used.

For both the pliers and snips; buy a decent pair. Many of you will already have these.

Multimeters are available in both Digital and Moving Coil/Analogue types. You can pick up a very basic one of either from about STGœ7.00 ( US$12? ). Prices go up and up as functions/reliability increases. You should be able to measure resistance and voltage ranges with these. A diode testing function is also useful, but not necessary. These are necessary to verify the integrity of a circuit or component, impossible to do without it in a complex circuit.

The resin-cored solder ( this is the normal type, but check when purchasing as you dont want un-cored solder ) is easily available. I prefer a thinner gauge to thick gauge, but its not very important.

The de-soldering tool or wick is important for when you screw up. Wick is a lot cheaper and works fairly well with a tiny bit of practice. De-Soldering tools take more practice but are a lot more effective in removing all solder, however for home use starting off Id recommend the solder wick.

How to Solder/Remove solder in a few sentences

Soldering works by heating the components/wire/printed circuit board ( PCB ) involved and applying the solder to the heated area for a very short time ( 1/2 secs ). The solder melts and flows over the components, the soldering iron is removed, the solder on the components, which should not be moved at this stage, solidifies and creates a permanent bond, which because its metal,, allows electricity to flow. The metal items to be soldered should be of a copper/tin/lead/nickel type substance, they should be clean, i.e. this means shiny for electronic components. The resin in the solder allows the solder to bond easier without oxidation . The soldered connection is called the joint. Note: It takes specialist equipment to solder/weld aluminium ( European spel ling ) or steel. If you use a Soldering Iron to melt or engrave plastic you will ruin the tip. After use coat the tip with solder and turn off. Allow the solder to cool on the tip.

To remove solder, heat the joint and place a length of solder wick on it, holding it in place with the soldering iron. The soldering will be removes from the joint by capillary action in the wick, (absorbed).

Obligatory Caution: Heated Soldering Iron Tips are damn hot. Be careful. Solder is a lead alloy. Dont eat it. Wash hands after use.

Components

I don't intend to get into all the different component types and variations, just some basics. All these should be easily available from an electronics supply outlet:
  1. Plenty of small gauge wire, preferably in both black and red colours.
  2. Selection of resistors. Preferably or watt. See later in text for more details of sizes and resistor colour-codes.
  3. L.E.D.s. Available in Red, Green, Amber and much more expensive Blue. Flashing L.E.D.s can also be useful.
  4. Light conducting source if necessary, fiber-optic cable or clear acrylic rod.
  5. Power source. Either a voltage adjustable DC transformer or a battery pack. Since I dont want to be responsible for anyone frying themselves Im not going to deal with AC
  6. Veroboard. This is a Brand name of circuit board which is pre-drilled, bare on one side with copper strips on the other side which can be cut as necessary, making it easier to assemble a circuit. Usually fairly cheap. Dont know what the US equivalent is, it may be Veroboard there as well.
  7. Black Heat Shrink tubing wide enough for the L.E.D.s or Fiber-Optic cable, also useful for insulating wires.
  8. White light source. Halogen bulbs, bicycle lamp bulbs, grain-of-wheat bulbs, etc.

A Basic example: Lighting the Halcyon ABC Warriors Eyes

This one is pretty basic but soon as I opened the kit I thought it could benefit from a pair of red L.E.D.s as the eyes.

You will need: two Red L.E.D.s, narrow gauge insulated wire, soldering iron and solder,, drill and cutter/small bit to take out the vinyl eyes, scalpel, no 11 blade, power source, ( a single 9V PP3 type battery is good for this), resistors, and battery clip or holder.

  1. First remove the excess vinyl from the front and rear head sections.
  2. Next, cut a hole in the rear head section to allow the cable access.
  3. Next is probably the most difficult bit. Using a small drill bit (1/32 ) cut a hole directly through the centre of each eyeball. Next I used a 1/64 drill bit ( really small ) to extend the cut-out of the eyeball. Next from the back of the head section, use a cutter to cut very slowly down to the eyeball without taking out the lids. A round cutter is best for this. You can them finish off with the No. 11 scalpel blade to align to the eyelids. You will need to cut a channel in each side of the inside of the head to allow room for the L.E.D.s and wire. If you cut too far forward youll take off the eyelids and need to re-model these slightly with milliput.
  4. Next you need to check the fit of the LEDs. What I found was that the eyeball doesnt take the LED precisely. There were some slight gaps at either side. I molded this up from the inside with milliput, (my first attempt was to use glue to fill the gaps but the glue made a mess of the LEDs, so I went back to Milliput. I used one spare LED and Superfine Milliput to make the correct fit.

    Another suggestion from Stewart in Liverpool is heat thin Plasticard and put the LED into it while its hot, thus giving a good fit. (Thanks Stu !)

  5. Assuming your test fit is O.K. next paint the inside of the head black, otherwise youll get some of the light shining through the vinyl, especially as you will have had to cut out some of the vinyl inside the head.
  6. Next TEST assemble your circuit and ensure its working. The longer leg of a LED (say it quickly! ) is the positive. Wrap this to the short leg of the other and then connect the positive on one and the negative on the other to the appropriate side of the battery. Both LEDs should light. If you mixed up the sides reverse it on the battery, both LEDs should light. However, only hold this for a few secs to ensure the circuit works.
  7. In order to properly build the circuit you must solder all connections together. For those familiar with it, I recommend shrink-wrapping all soldered connections. IMPORTANT: Because each battery type is different and the chemical make-up of the battery determines the current ( Amps ) you MUST add a resistor to limit the current, to prevent the LED shorting out and blowing/burning out. Especially in this case, as once its added theres no going back. However with a current limiting resistor in place and dont change your power source, you should have unlimited lifespan from the LED. For wiring the Halcyon I used a PP3 Battery. Current is quite low from these batteries, I calculated a 375W Resistor.

    To make it easy, without calculations, try a or Watt 1 KiloOhm resistor, connected to the positive LED leg. If you need greater brightness, halve or quarter either of these values if you are using an Alkaline or Ni-Cad 1.5V battery.

Note on Resistors, LEDs

If you are interested, this will be helpful for other circuits; Resistors are measured in Ohms and come in different resistance, symbol W and power usage symbol W, ranges and also different manufactured types. The types dont matter here.

Note: the values of resistors can be determined from the colour bands on them, their colour code. See The Resistor Color Code Chart for details on how to read it.

Resistor values are not quite straightforward. The typical values are; 1.1, 2.2, 3.3, 4.3, , 5.1, 5.6, 6.2, 6.8, 7.5, 8.2, 9.1, 10, 11, 12, 13, 15, 16, 18, 20, 22, 24, 27, .100, 110, 120, ., 200, 220, 240, 300, 330, 360, 430, 470, 520, , 560, 620, 680, 750, 820, 910, 1000, (1k), 1.2K, 1.5K, 2.2K, ..etc. As you can see its not a straight increase of values. There are intermediate values available, but for modeling purposes you dont nee this accuracy.

The main ranges of Power Consumption for our purposes are; , and 1 Watt resistors.

Also for our purposes, they can be wired in two different ways: series and parallel:

Series
leg of one connected to the leg of the next (daisy-chained); Series. Values of R1 and R2 are added.
Parallel resistors are connected beside each other;
Parallel: Values are given by; R1 x R2 R1 + R2 However this formula is only used for two resistors in parallel. There is a different one for more than two: ( 1 = 1 + 1 + 1 .) R R1 + R2 + R Series is useful for adding up smaller values to give a larger, e.g. 1 K W + 1 K W = 2 K W Parallel is useful for splitting larger values to give smaller, e.g. 2 K W x 2 K W = 1 K W 2 K W + 2 K W

Light Emitting Diodes (LEDs)

These are semiconductor devices, which emit light when correct current and voltage are applied. For red LEDs voltage is 1.5V and current (I) of 18mA. For green diodes voltage rises to 2.2V. LEDs are connected Forward Bias i.e. the anode (positive terminal) is connected to positive with respect to the cathode (negative terminal). For most model circuits which are operated by battery or DC transformers, this means positive leg to positive connection and negative leg to negative connection.

They are available in Red, Green, Amber, and Blue, although the Blue is rare and more much more expensive. There are also flashing LEDs, however they do not flash in synchronous time so they should not be used in array as a light sequence; however they can be useful as simple timing devices in a circuit, although only as a control for normal LEDs, e.g.: using a flashing LED to switch on a transistor driver circuit for other LEDs, or even a simple current feeder to (maybe) two LEDs in series, although I havent tried this.

In Closing

There are a lot of potential uses for electronics in kits, running and navigation lights, search- and identification lights, sirens, speakers and of course, eyes, screens, dials, etc. There are books available for electronics in models. As with all else, some practice and some care, along with the right tools, will go a long way, regardless of electronics knowledge or background.

If I ever get time Ill try to add some circuits with diodes, transistors and 555 timers, but don't hold me to it, o.k.?

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