Molex connectors are the electromodder's best friend. They provide stable, accurate power on tap wherever you need it inside, or even a little outside your case. If you're reading this you'll probably have pushed in and pulled out a good few molex connectors in your time, yet most people don't know what those 4 wires are. All that you need to know about a molex is what voltage each of the lines are, take a look at this diagram:

Components are the building blocks of every circuit. We connect them together with wires or copper tracks to make circuits, but it's the components that do all the work. The first thing we're going to be making in this series is a simple LED light for your case which will use two of the most common components. This will take us through what a resistor does, what an LED does, how to calculate resistor values and how to read circuit diagrams... oh, and you'll get a pretty light at the end. What more could you want?

I'm pretty sure you'll have come across LEDs before: the average modders case probably has about a dozen of the things; many of you will also know that LED stands for Light Emitting Diode. They come in all shapes, size and colours, if you buy them fresh they might look something like this...

This is why the legs are different lengths: the positive leg is always the longer of the two. If you connect an LED the wrong way round it won't kill it - it just wont produce any light.

So, from what we know about LEDs and molex connectors gives us this circuit diagram. The direction of the LED is indicated by the direction of the triangle, the negative short leg is always the point of the triangle:

LED Forward Voltage: 2.2V

LED Max Current: 25mA

Power Supply: 5V Molex

So, using that formula we'll take the LED Forward Voltage away from the Power Supply to give 5–2.2 = 2.8V. This is the voltage the resistor needs to take across it. Now we need to divide this by the Max Current – this is where most new comers go wrong. The formula expects the current to be in amps, but we've been given the current rating in milliamps. Now, 1 milliamp is one thousandth of an amp, so to convert from mA to A we need to divide by 1000. This gives us a value of 25/1000 = 0.025A. We can now divide 2.8/0.025 to give us the value of resistor needed! The answer is, drum roll please, 112Ohms. We can't actually use this value for reasons I'll go into in the next part when we'll be covering the practical implementation of the circuit in our rig but we'll pretend we can for now. Our final circuit diagram now looks like this:

That's all for this part folks. In the next part of the series we'll be using the circuit diagram we just worked out to make a working LED light for our case, looking at the practical side of the theory we've covered. If not all of what I've covered is sticking in your brain, don't worry about it. Electronics is far easier to learn by doing than by reading up on equations and diagrams. As the series progresses you should find yourself getting more of a 'feel' for it and getting confident enough to tackle more complex circuits.

October 15 2020 | 14:00

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