Sorry for the lack of photographs and excess of external links, I hope to add some example pictures as I can find/produce them.
Using LEDs on a model may seem like a daunting task, but in reality it's not so difficult. Just keep in mind that your project is likely to take quite some time to complete (especially if it's your first LED conversion).
Some basics for this guide:
1) Read the whole article as most parts of the accutal wiring/assembly can be completed in no particular order as long as certain "rules" are followed.
2) Know "THE" equation before looking for leds so you can find the correct resistor. That equation is (V in - Vf)/If = resistance in ohms needed.
V in = Voltage in from source (your total battery voltage)
Vf = the Voltage drop from each led (this should be listed on the LED's packaging, but might also be listed as Vf max or simply Vmax depending on manufacturer)
If = the maximum forward current in
Amps each LED can use (This should also be on the packaging, but remember LED’s list milli-
amps, so don't forget to move the decimal place in your equation as 1mA = .001A
Example: I have a 4.8 volt battery and an LED with Voltage drop of 4.0 vlots and a max forward current of 30mA. (4.8-4.0)/.o3 = 26.666. You'll need a resistor as close to this without going under. I used a 33ohm resistor in this case which worked fine.
You might also need to know wattage, so far I've been able to manage with resistors rated at 1/2 watt. I'm sure I could go lower, but not how much.
3) You'll need to solder wire to lights & resistors. You'll need the solder (I've been using
http://www.radioshack.com/product/index.jsp?productId=2062725&numProdsPerPage=60&retainProdsInSession=1), a soldering iron, and probably something like this:
http://www.radioshack.com/product/index.jsp?productId=2104639 just to keep all your parts steady while soldering. Keep in mind that most soldering irons get rather hot so if you've got small children in your home you might need to take extra precautions to keep your little ones safe.
4) If this is your first time soldering here's a good tutorial
http://www.youtube.com/watch?v=I_NU2ruzyc4. Just remember that for most of your work here you won't really be needing to solder to a board, simply wire to wire, but the techniques taught here are essentially the same and you'll find them useful.
5) Take your time, never let yourself get rushed 'cause there are a couple of simple mistakes you can make that can botch the whole job.
6) I recommend reading
http://www.nugax.com/WH40K/Crusader.html. I learned a lot of what I'm going to go over here from this tutorial, but most of his tutorial is pretty specific to customizing a Land Raider & simply used it as a basic guidline from which I made my own design. I hope to provide a more generalized guide here.
7) Be flexable, your project will likely not follow the initial plans. When you run into this situation, just stay calm and try to rework your plans as little as possible to accomodate for what's gotten in your way.
Now to the actual task.
Research Phase:
1) Pick a model you want to light up and acquire it. It's got to have suitable space for lights, wires, resistors, a switch (maybe two) and a power source. Take note of how many lights you'll want to use. Also, unless you have the means to completely disassemble an old one, you'll need to start with a new unassembled model. My first LED project was a Land Raider and I found the aforementioned guide (part 6 above) when I was in my researching phase of the project.
2) Now that we have a model before we do anything else, look the parts over and really study the assembly instructions. Take notes on where you think things will fit the best and if necessary, take measurements & draw basic diagrams of what you think the wiring should look like (this will make more sense a little later on after I cover some of the wiring aspects). You'll want to at least have an idea how your curcuit will run. Think of it as an oval race track, it needs to start at your battery's positive lead, go through the resistor, continue through the LED (in the right direction which is positive in through the anode and out through the cathode. The anode/cathode should be listed on the LEDs packaging) then back to the battery's negative lead.
3) With a basic plan in mind collect the rest of the materials you'll need to complete the project. Get all the LEDs you'll need (possibly some extras just in case & if this is your first time working with them I highly recommend it), the appropriate resistors, and wire, lots and lots of wire. In the case of basic
GW models I've used either 22 gauge wire or magnet wire depending on the situation. If you find you need to go as small as using magnet wire, be aware that it doesn't have much insulation on it (usually an enamel coat at the most) so your wires need to be rather seperated.
Work Phase:
1) You'll have to pretty much prime this sucker on the sprue. There's no real option to assemble the model, prime it, paint it, then wire everything in. Just assemble what you can, add wiring, paint if necessary, and repeat as needed. If you're familiar with the Land Raider model this might help. I started by assembling (but not gluing yet) the basic core box of the model (minus the external plate on the back which I magnetized so I could use it as a battery cover), cut the holes I needed for my wiring & LEDs, painted each piece, glued it all together (had to put the interior engine panel in front of the floor & wall moulding to get extra space for the battery, but shaving a little off the top of it caused it to fit perfectly) then added my wiring before assembling the tracks. I hid all my wiring inside the tracks above, below and inbetween the door/sponson points. My battery and switch ended up in the back behind the magentized panel.
2) Make sure you wire each LED in this order positive lead, resistor, LED, negative lead. To save space (assuming you've got a number of lights in close proximity), you can split your positive lead as far out as you can, but before any resistors are connected, and can continue to split each time you need to add a resistor/LED. Again, in the case of my land raider I hid a resistor just above each door/sponson point for the two lights on either side, and I put my interior lights entering from the sides, near the ceiling so I was able to hide the LED and resistors for those in the space between the doors. The line ran from the battery to the top of the doors, split one to the resistor, one continuing, split one to each of the remaining resistors. Connect the negative lines together as soon as possible so you can get down to one wire running back to the negative lead and again save space. Saving space will help you have a little more play when it comes to final assembly of your model.
3) Unless you're only lighting up single LEDs spaced quite a distance from each other (creating completely seperated circuits), wrap your resistors and all exposed wiring joints in electrical tape. This will prevent accidental connections and give an added layer of insulation.
4) You can actually wire in the switch before or after the LEDs, it doesn't really matter since all it does is break the circuit causing a stop in power flow. However, it does have to be between the power source on one side or the other and ALL LEDs that you want controlled by that switch. I find it easiest to just wire it nearest the battery, but you may want it elsewhere on the model so you won't have to open any compartments to turn it on/off. If you want to have multiple switches to turn on/off different lights then you'll need to split the positive line wire in your switches and treat the line after each switch as a separate circuit to track.
5) Wire the battery/battery housing into the circuit.
6) Before you finish assembling and immediately after you finish assembling your model (but before the glue has set) BE SURE
TO TEST THE LIGHTS!!!! You might need to resolder something that's come loose.
7) Paint to your liking and you're done.
Personal Tips
Battery choice:
There's a ton of options for batteries anything from wafer thin watch batteries, double A, triple A, to rechargable NiCad/NiMh/LiPo. Keep in mind that the more lights (and consequently resistors) on the project, the faster your battery will drain. Watch batteries are expensive and will drain rather quickly, you might get away with one or two
these if you're only lighting a single LED. Standard or even rechargable AAs/AAAs might seem more feasable/cost effective, but they're pretty big for the scale of most models in our hobby. I personally went a slightly more expensive route, but it's saved me space and it's rechargable. I used a NiMh battery from a 1/36 scale R/C car. Ran me a whole $12 (if you need the charger it's another $20 or so, but you'll only need one if you stick with this battery type). Here's a link to it:
http://www.losi.com/Search/Default.aspx?SearchTerm=36_Std_NiMH (If you want a charger go for the outlet charger, the box shaped charger is battery powered, so you'll fill it with
a bunch of
AA batteries and it'll charge your NiMH until it runs out of juice). You'll also need:
http://www.losi.com/Products/Features.aspx?ProdId=LOSB0847 It runs about $3. You'll need it so you can remove the male connector to wire into your project. This allows you to remove the battery for charging and eventually replacement. I'm not telling you to use this setup, just letting you know what's worked best for me. Use it at your own discretion.
Beginners:
Help yourself early, if you have multiple LEDs that require resistors of differing values, mark the package they're in with the resistor rating required so you don't have to punch up the equation every time you forget which resistor goes with which LED. Just don't write over the ratings on the LED packaging, just in case you need to double check your math (personally, I'd just use some masking tape and write on it).
You'll probably be nervous/anxious about working with LEDs and having the potential to completely ruin an expensive model (face it, these things aren't cheap and I was nearly jumping out of my skin the first time I tried this). Give yourself some extra experience with the soldering/wiring aspect by purchasing extra LEDs and the appropriate resistors. Then take one each of the resistors & corresponding LEDs, solder them together (remember to solder the resistor to the anode and not the cathode), solder a wire to the resistor and one to the cathode then connect your battery to the appropriate wires and make sure it lights up. Remember this has to be your full power source so if you're using more than one standard battery for your final project, you can't cut corners and just hook one battery up to test. Most standard batteries (other than 9volt batteries) are 1.5 volts EACH, so if you're using 2
AA batteries you'd have a 3volt circuit. If you mess with your voltage, you will no longer have the correct resistor.
LEDs:
There are a wide variety of LEDs you can use, so far I've only used 5mm, 3mm, and just started working with some that are called SMT. This stands for surface mount technology. Sometimes they're called SMD, or surface mount device. Whatever they're called they're very tiny LEDs (as in, I have one that's 1.8mm X 0.6mm X 1.2mm. VERY tiny indeed). You'll need a magnifying glass to even attempt to work on these. Whatever LED you choose to use, be certain that it's the right one for your job. It has to fit in the space you want to use it in, too big and you're outta luck, to tiny and it'll either look funny or be a lot harder to do than it has to be.
Hope this is helpful to someone,
good luck, and I hope to continue to see many more beautiful models here!
Here's some pictures to help, I couldn't figure out how to get them attached anywhere but the bottom of my post. Again, sorry for the quality, but they should give you some idea.
