Lessons: #3 Our Very First Circuit

Lesson three is upon us! Here today we are going to (kinda) make our own circuit. We know almost enough already to do so so why not? So... what kind of circuit? One that will light up an LED, or a light emitting diode. Now, before we can get started, we need to discuss something, and that'd be a component called a resistor.

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Remember from lesson 2 when there was the water tank analogy, and the width of the spout was the resistance? Well, sometimes you really need some resistance in a circuit for it to function properly. Imagine your spout was really, really wide and there was an enormous amount of volume traveling through it and you were trying to fill up a small cup. The cup would almost immediately fill up and start to overflow, spilling water everywhere. So, in other words, a complete catastrophe. Same concept goes for electricity. Imagine you're building an LED circuit. The LED is your cup, the battery is the tank and the resistance is your nozzle width. Now, you obviously need a certain resistance so your cup doesn't overflow too quickly and, well, one that's not too thin so the water doesn't slowly drip out like a faucet in an old building. You want a resistance that will fill your cup up right at a nice pace. Now, back to the circuit. You need a resistance that will keep your amps right in the LED's butter-zone. So, how do you get that resistance? Use a component called a resistor! A resistor is a component that will deliver a certain amount of ohms to your current so the amps are satisfactory. Now, how do you find out how many ohms you need? 10? 1,000? Simple. Do you remember Ohm's Law? You know your voltage because you have to know what kind of battery you're using, and you also know your amps because your LED will tell you how much you need. So, let's figure this out.

Let's say we have 2 AA batteries that gives out a total of 3VDC (volts direct current) and the LED, for our convenience, operates at 3VDC at 25mA (milli amps). So, we know our numbers, so all that's left to do is plug and chug! I = V/R plug our numbers into our equation: 0.025A = 3VDC/R. Once you do the math, you should come out with 120 as your answer. So, for your LED to opperate well, you'll need a 120 ohm resistor in your circuit!

For more awesomeness, head to lesson 4!