How to add leds to your models

I have had several people asking me about how I add LEDs to my models and display boards, so I decided to do a step-by-step guide on how I do it. I have split it up into two parts to get us started. The first part is about how to properly solder, and the second part is about building a basic LED circuit!

The materials and tools we will need are:

  • LEDs
  • Wire
  • Battery
  • Battery holder
  • Soldering iron
  • Solder
  • Wire cutters/strippers
  • Heat shrink or electrical tape
  • Lighter or heat gun

Part One:

The first step is to get two pieces of wire. Color is irrelevant but for our circuit it helps to have two different colors to keep your circuit parts straight. Strip the wire covering (insulation) from the ends of each wire, approximately a half-inch. Depending on the gauge or thickness of the wire you may need to strip more or less of the wire insulation.

 

 

When using the wire strippers, the wire will fit into the indents on the jaws of the strippers. Try not to remove any of the underlying wire, just the insulation.

 

 

 

 

Next, we will twist the wires together using a ‘western union splice’.  Begin by centering the exposed wire together at the center, then bend them over each other in opposite directions. Continue doing this until the ends of the wire are flush.  The ends of the wires should not extend over the insulation of the other wire.

Now we can get our soldering iron.  My favorite iron is a butane powered one, but the simple & inexpensive pencil type that you plug into the wall will do just fine for working with LEDs. We will also need the proper solder for working with electronics.  The solder on the left is rosin core solder that is specific for electronics. The solder on the right is solid core lead-free solder. This is used for plumbing and will not work for electronics.

 

 

Plug in your soldering iron and let it fully heat up. If you are using a butane iron, ignite it and set the temperature to a medium or higher temperature setting. In the picture above, there is a large soldering iron with two prongs.  This will work, but it will get *very* hot *very* fast, and may end up melting your insulation on your wires or your electronics.

Next, you will apply a small amount of solder to the tip of the soldering iron.  This is called “tinning the tip”.  It allows a better contact point from your soldering iron to the item you are attempting to solder.  It is not used to actually do the soldering.

 

 

Then, set the union of your wires on the end of the soldering iron, and let the heat from your soldering iron soak into the wires.  Don’t do this too long or it will melt the wire insulation.  Apply the solder to the top side of your joint.  The solder should flow into the strands of wires.  Do not use too much or it will soak too far into the wire and cause it to become hard and brittle.

 

When you are finished, your solder should dry/harden quickly and should have a clean, shiny appearance.

 

Now, the best practice is to cover the solder joint with a type of insulation.  The easiest type is electrical tape, but you can also use heat shrink.  Heat shrink will basically act like the original wire insulation.

To apply heat shrink, cut a pice of the tubing so it is about one-half the size of the splice. Slide it over the joint, and apply heat. I will usually just use the heat from my iron, but if you are not careful, it will melt.  You can also use a lighter or a heat gun. It is best practice to cut a length of the tubing and slide it over your wire, before you solder your joint.  If you don’t have an open end of your circuit, and you already solder the joint, you can just use electrical tape for the insulation.

 

To use the electrical tape, simply cut it to length and wrap it completely around the joint.

 

Now you have a fully soldered and insulated wire splice!

 

Part Two

For this part, we will use our new-found soldering skills to build a basic circuit.  To start, we will need the same tools as above, and we will need a battery holder, wires, and an LED.  I typically get these from Amazon. Unfortunately, all of the local electronic stores around me have closed.

Diodes are fairly simple creatures. They work as a one-way valve in the electronics world. You can see on these ‘Light Emitting Diodes’ that one of the terminals are longer than the other. The longer terminal is the terminal that connects to your positive battery contact (+) and the short side will go to the negative (-). If you reverse this, the electricity will not flow and the light will not illuminate.

One fun thing you can do with a button cell battery is sliding the LED terminals on either side of the battery, and it should illuminate if you have the terminals on the correct side.  For most of my led work, I use these batteries. If you use other batteries, be sure not to use one with more than 3-4 volts for 1-3 LEDs. Too much voltage will burn out the LED very quickly.  If you have more than a few LEDs in your circuit, you may need to increase the circuit voltage.

To build our circuit, start by soldering the wires to your battery holder. There are many different types of battery holders to choose from. This is the type I used for my last project, and it is small enough to hide inside of a model. The batteries I use are CR2032 as well as the corresponding holder. They will continuously illuminate an LED for 3-5 days, depending on the color of the LED. I also purchased a bulk bin of different colored LEDs for only a few dollars; it has 3mm and 5mm sizes of red, blue, yellow, green, and white LEDs.

 

To start soldering the wires to the battery holder, tin the terminals with solder, then solder the wire to the battery terminal holder. (For this circuit, I used a solid wire.  It is more rigid than stranded wire, but it is more difficult to work with).  Now, put a red wire on the positive side and black wire on the negative side.

 

 

Solder the other ends to the LED.  Remember: the longer terminal of the LED will go to the positive (red wire).

 

 

 

Insert the battery, and behold!  You have a basic circuit!

If you want to go a step further, you can add a one-off switch to either wire, and you can control the light from many points on your model. I usually do this by removing the battery, but depending on your build, a switch may be more practical. On my dune crawler, I fashioned it so that the roof is magnetized to the body. There’s a  lot of room in the body to hold the battery and LEDs.

As you can see, I soldered the LED directly to the battery holder for the Neutron laser. It is already mostly hollow, but I needed to make room for one of the 3mm LEDs using a drill bit. I drilled a hole in the part that connects the laser to the body of the dune crawler, and soldered the wires to the LED and assembled all of the parts.  After I was finished painting, I soldered the wires to the battery holder as well.

If you have any questions, or would like some help with your next lighting project, please feel free to ask them in the comments below. We would love to see what you are working on!

Shawn

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