With our last post, we got all of the materials needed for creating a LED circuit. The next step is learning how to create a working circuit to get your desired effect and bring your model to the next level.
So just like the rest of Warhammer 40K, let’s get into some MATH. These calculations are important because one number, one miscalculation, or one little error can cause issues that are going to drain batteries, drain resources, and waste money. Trust me; I have blown plenty of LEDs, drained batteries, and wasted solder and wires unnecessarily. Hopefully, my mistakes will help you avoid making the same mistakes. Remember, with miniatures, mistakes generally lead to more money being spent.
Here is the Formula that you will be using for everything:
R = (Vs - Vf ) / I
R = Resistor (measured in Ohms)
Vs = Voltage (from the battery or source)
Vf = Voltage Drop (this is the voltage across the LED)
I = Current (measured in Amps)
This is just the basic formula that you will use with every single circuit you create no matter how simple or complicated you chose to make it. Let’s take a look at my Dreadnought that has become a staple on my posts (mainly because it is the first one I did and I think he looks awesome on the table top). He is powered by two 3V CR2032 watch batteries. The LED is a Square Blue LED from RadioShack, Blue LED, that has a Voltage of 3.5. The current of the circuit is 20 mA or 0.02 A. I can’t remember what Resistor I used, so let’s do a little math to figure out the resistor needed.
If we were to lay it out on paper it would look like this:
R = ?
Vs = 6 V
Vf = 3.5 V
I = 0.02 A
In the formula it would be:
R = (Vs - Vf ) / I
R = (6V - 3.5V) / 0.02A
R = 125 Ohms
The resistor needed would be 125 Ohms. Now there is not a 125 Ohm resistor but you can instead take a slightly larger resistor like a 150 Ohm resistor like the one seen here, 150 Ohm Resistor, and it will protect your battery, your LED, and your model. The one thing that I haven’t talked about is the switch.
The switch is an integral part for any model. It can be hidden on the model, added into the model, or hidden on the base, like my Dreadnought. There are a variety of switches to use, but for this one I went with a simple single pole single throw switch or SPST . This means that it will have two positions: on and off.
Now that you have everything: Switch, Resistor, Voltage Source, LED, wires, and soldering iron, you are ready to roll. I would suggest testing soldering on just two blank wires until you have a steady hand and know how to solder the components together. I suggest looking at tutorials online through YouTube because it is easier to watch and listen while performing the techniques than to read and try to perform. Once you have practiced enough, you are ready to start. Key things to remember: power flows from the Positive ( + ) pole to the Negative ( - ) pole. When soldering it is also important to remember that in general, it should go Power Source, Switch, Resistor, and finally LED. This is the easiest way to make a circuit and will help be the blue print for all your models going forward.
You have the tools now to go forward with a single LED circuit. Now it is just practice and determination to set you on your way. The next post will be a step by step (with pictures) procedure post where I will be lighting up a Tau Devilfish for the army that Evan and I will be starting work on in the future. If you wish to follow along, you can use the model of your choice and try your hand at LED work.