Capacitors & Inductors basics
Autor: fumo | Publicado: 2011-02-21T20:37:00-08:00

Today we're going to talk about capacitors and inductors. We are not going to talk so much about them because most of times they are used in analog circuits and not on digital circuits. The inductors we use are normally in motors or relays, etc... And we actually don't see it as a common inductor.
The reason why they are on the same post is because I don't use them very much so I can't really talk a lot about them.
Take a look at these videos from Collin Cunninghan:

Capacitors:&nbsp;http://www.youtube.com/watch?v=ZYH9dGl4gUE

Inductors:&nbsp;http://www.youtube.com/watch?v=STDlCdZnIsw

So capacitors are used to store energy, and one good application for that is to remove the noise from a DC power supply. Like this:



So this is the basic idea of a power supply. It's divided in this "blocks". The first block is the one which will make the voltage from the wall outlet a bit lower and more useful for our circuits (like if you using an 110v wall outlet, it maybe something like 36v or any&nbsp;other&nbsp;lower voltage). The second block will eliminate the negative part of the signal, which most of times is not needed. The third block will take off this "holes" (the noise) in the signal and it'll be like a straight&nbsp;line which has no noise. The forth block will regulate the signal to the voltages we will need. For example if we need 5v and 3.3v from the same power supply, instead of using 2 transformers, or anything else to regulate that, we can use zener diodes and some transistors or even some nice voltage regulators ics for that.
The third block most of times are built with capacitors and inductors.
When we connect a crystal to a microcontroller, we need to add some capacitors. They need to be the right values because wrong values will give different oscillation, which should be avoided.
Adding capacitors together to get a bigger capacitance value, it’s a bit different from adding resistors:


When we add capacitors in parallel we have a capacitance C equals to the sum of the capacitance of those capacitors. So:

Parallel -&gt; C = C1+C2+C3

Series -&gt; 1/C = 1/C1 + 1/C2 + 1/C3

Well, I never needed to do this, but may be useful for someone else.

Take a look at this video using inductors to create an electronic xylophone that plays itself:
http://www.youtube.com/watch?v=sR3xmof8rZY

Well, there are a lot of advanced things here. We will talk about microcontroller code later. But that shows you a bit of what can be done with inductors and that making your own may be useful for custom design that fits your projects.

There is something about that video that will be useful when using transistors with inductors. Look at this schematic:


This is the schematic to control a 12v relay to power a 120v lamp. This 2 are the same schematic, but in a simulation where the left one has the lamp off and the other has the lamp on. A relay is the component with the label "RL1" and has an inductor inside of it. So in order to use it with a transistor, we need to use a diode connected to the relay with inverted orientation, like the schematic.&nbsp;Instead of a switch, we could use the output of a microcontroller or any kind of digital circuit.&nbsp;
Relays are good to control high voltage or AC devices like lamps, AC motors, etc. A relay is an electromechanical component, so it means it has some moving parts inside of it... and because of that you should avoid making some fast "on and off" changes... like PWM on that lamp for example. (We will talk about pwm later).
Well, if you saw the 3 videos and read everything, you probably know what you'll need to understand next posts.
Next time I'll talk about diodes, also I probably not going to talk much about them, but a little bit more. (I believe)
Cya next time.