Bob Hunk's LED-lit Marines Tutorial
++ EDIT August 2018 - You can now find my revised and updated LED miniature tutorials at chrisbuxeypaints.com ++
As promised, here's my tutorial for putting LEDs inside Marine helmets. The photos show this technique applied to a 'true scale' Marine, but it can equally be applied to normal scale Astartes.
I strongly recommend reading through the entire tutorial before starting work, just to make sure you have the necessary skills and tools required.
I have a separate tutorial about selecting LEDs and designing circuits for models and basic soldering on the PCRC website. This tutorial assumes you've either read these, or are familiar with basic circuit design and soldering techniques.
1. Start by selecting the type of battery you want to use. I prefer the CR2032 or CR2025 coin cells. These are the lithium memory back-up batteries you find in PC motherboards, among other things. I like these because they last a long time, can power the brighter 3V LEDs and most importantly, because they have a low profile that will fit inside a standard base for a 28mm model.
You'll also need to select a suitable battery holder. Many types are available and a selection are show below. Again, it's important to pick one that will fit inside your base (possibly with a bit of trimming).
2. I've chosen the Keystone 1060 coin cell holder and the 30mm rolled shoulder base from Wyrd Miniatures. This is just personal preference, as long as your battery holder fits inside your base then you should feel free to use any brand.
3. Cut out the interior of your base using a craft knife or similar. Make sure you leave the rim intact. Admittedly this is easier with this style of base. Also trim the corners of your battery holder so it will fit into the resultant hole in the base.
4. Insert the battery holder into the base. Make sure the battery is in the holder for this step. Position the battery holder so that the side that you insert the battery is face down (this will allow you to change it without disassembling the model) and so that the bottom of the battery holder is flush with the lower edge of the base. This should mean that when you put the base on a flat surface, it is level.
Once you are happy with the position of the battery holder, secure it to the rim of the base with a couple of small dabs of superglue. Be careful not to get glue on the battery!
Note: Some battery holders have a clip that is pushed outwards when the battery is insert. That's why it's important to have the battery in place at this stage, otherwise you may find that when you insert the battery into the completed model, the clip now protrudes below the rim of the base and the whole thing is suddenly wonky.
5. Generally I think it's a good idea to include a switch. This allows you to turn the LED off when not in use without having to take the battery out each time. But if you don't mind doing that then I guess you can skip the switch!
If you do want to include the switch, then you'll need something very small. PCB slide switches will normally do the trick, but check the dimensions! A switch with a length of 5-10mm is ideal.
You can secure the switch to the top of the battery holder with a small dab of superglue on the outer case of the switch. Make sure you don't get any inside the switch though, as you risk either jamming the mechanism or accidentally insulating the contacts!
6. Next add some wires. You can either use insulated or enamelled wires, but do not use bare metal wires as the wires will be touching and you'll get a short circuit. As you can see in the picture below, one of the wires is soldered directly to one of the battery holder terminals, while the other is soldered to the other terminal via the switch and a short length of wire.
Polarity is important for LEDs, so make sure you know which wire is positive and which wire is negative. Use different coloured wire to indicate this if you think it will help.
You'll want the two wires to be about a third longer than the intended final height of your miniature, just so you've got some slack to work with.
7. Drill a hole through the torso of your model, right down the vertical centre. As you can see in the picture below, the drill emerges in the middle of the neck socket. It's a good idea for the width of the hole to be slightly greater than the horizontal distance between the outside of the two legs of your LED. If the width is narrower then there is a risk the legs will be pushed together and short circuit.
8. Now drill a hole through one of the legs of your model. This hole should be wide enough that it can accommodate both of your wires side by side. Ideally the drill will enter through the base of one of the feet and emerge in the centre of the waist, that way it will line up with the hole in the torso. However this can be quite tricky, and as you can see in the picture below, I missed on this occasion! Not to worry though, any mistakes like this can be covered with green stuff later.
9. Feed your wires through the legs and the torso.
10. You'll now need to drill a hole in the base of your Marine's helmet that is wide enough to accommodate the LED. Don't worry if your drill is so wide it destroys the 'neck' of the helmet, you can always fix that with green stuff later. Remember that you can file down your LED if you need to make it a bit smaller to fit in correctly, just so long as you don't file all the way down to the p-n junction (the metal-looking bit inside).
In my ordering LEDs tutorial that I mentioned earlier, I explain that I prefer to work with 1.8mm LEDs. Here's a scale shot next to a helmet for reference; as you can see they're the ideal size.
As I'm working with resin helmets, I've drilled the hole to just behind the eyes. As the resin is quite thin this has allowed the LEDs to shine through the eye sockets without actually having to drill them out. If you're working with plastic or metal helmets, then you're probably going to have to physically drill out the eye sockets with a miniature drill for the LED to become visible.
11. Now insert the LED into the helmet, using a cocktail stick or pair of thin tweezers to help push it in if necessary (push on the LED itself rather than the legs). LEDs tend to emit most light vertically rather than horizontally, so you'll want to bend the top of the legs so the top of the LED points directly towards the eyes of the helmet. The easiest way to achieve this is to hold the legs with a thin pair of pliers or tweezers directly under the base of the LED and bend the legs around that.
Once you are happy with the position of the LED, secure it with a tiny dab of superglue. Make sure the superglue does not get between the top of the LED and the helmet's eyes!
12. Trim the legs of the LED and the wires (although you'll still want to leave a bit of slack as shown below) and secure them ready for soldering (I use blu-tack to hold them in place). Double check you have the polarity correct at this point. PRO-TIP: The longer LED leg is always the positive (a.k.a the Anode).
Re-read my tutorial on soldering LEDs if you're not feeling confident at this point, paying particular attention to section 3.
13. Now solder the LED legs to the wires! Once you have done this, operate the switch to check that everything works. The LED should now illuminate. It's always worth checking at this point because there's nothing worse than having to take an assembled model apart to perform fault finding. In fact it's worth operating the switch to check that everything still works after each of the following stages, just to make sure you haven't caused any accidental damage during final assembly.
If you're working with a resin helmet then you'll probably notice at this stage that the whole helmet glows rather than just the eyes. Don't worry though, any areas that are painted will block the light - so obviously paint everything but the eye lenses!
14. Now pull and slack of the wires through the bottom of the foot and position the legs, torso and head how you want them arranged on the finished model. When you are happy secure them in place with superglue. Any excess wire should be coiled under the feet at this point.
15. Once the superglue applied in the previous stage has dried, you can now hide the battery holder and any spare slack wire under a layer of milliput (or similar). Be sure to:
a) Not get milliput on the battery itself, and
leave the top of the switch exposed so you can still operate it. I tend to position the switches at the back of the base, so it isn't visible in this picture.
16. And there we have it, one LED lit Marine! All that remains now is to complete the assembly of the model, fill any gaps around the neck and/or cover any exposed wires at the hips with green stuff and paint it, but you don't need me to tell you how to do that. I do have one final important point to note though, during spray undercoating, make sure you cover the helmet eye lenses and the top of the switch with blu-tack (or similar) so that they don't get spray paint in them!
I hope this tutorial is helpful! If you have any questions then please feel free to ask.
Edited by Bob Hunk, 29 August 2018 - 03:49 PM.