Today I'm going to talk about diodes.Diodes are electronic components that allow current to flow in only one direction.Sounds simple right?It really is but there are several types of diodes and I'm going to talk about them.
Here's how a "standard" diode looks like.It's also called rectifying diode.
It just allows current to flow in one direction.Those wires you see sticking out of the diode are called electrodes.
The one on the left marked with the grey band is cathode(-).The other one is called anode(+).
If you connect the positive side of a battery to anode and the negative side to cathode current will flow.If you connect it the opposite way current won't flow because the diode blocks it.
(notes:
-never connect a diode to a battery without a resistor to protect it
-if you connect the diode the right way a voltage of 0,6V is required for the current to flow)
Now i'm going to tell you how diodes are made.
They're made of semiconductors(mostly silicon or germanium).
This is a diode symbol on the left and a semiconductor on the right.
(note:K is cathode,the reason it's K and not C is that in my language the word for cathode starts with K and this is the only picture i had)
As you can see the semiconductor has two parts(p and n).As you can guess "p" stands for "positive" and "n" stands for "negative".In the positive side there are more gaps(+) and in the negative side there are more electrons(-).A gap is made when an electron leaves an atom.The electrons that left the atoms in "p" side go to the "n" side.Now when you connect a battery properly electrons from the (-) side of the battery will flow to the "n" side and make it even "more negative".Then the electrons start crossing to the "p" side filling in the gaps.The (+) side takes away the electrons from the "p" side.That way the current flows.
(note:
-in the old days when electricity was discovered it was thought that the current flows from (+) to (-).Actually the current(current is directed movement of electrons) flows from (-) to (+) but changing the general perception of current flow would be too difficult so the "wrong" theory remained)
Now the other types of diodes.
Other commonly used diode is light emitting diode (aka LED).
It also allows the current to flow in one direction but when current flows through it it glows.
Here's how LEDs look like:
These are red LEDs.The other most common colors are green,blue and white.There are also double-color diodes but i will maybe talk about them later.
As shown in the picture the longer "leg" of the LED is anode.Cathode is the shorter one.Cathode is also
larger.In the top picture LED is shown from above.The side with the part cut off is the side where the cathode is.The bottom picture is shown how LED is drawn in schematics.
The next diode I'm going to talk about is called a zener diode.
As a rectifying diode when connected to a battery "properly" current will flow.If it's connected the "wrong" way current will also flow but the voltage on the ends of the diode will be limited depending on the diode model.If a zener diode is made for 6V and you connect it to for example 12V a lot of current will flow through the diode (it won't be damaged) and the voltage on the ends of the diode will be 6V.It can be used to limit the voltage for some components or devices that are made for voltages lower than the one available.
These were the standard diodes.There are couple of more types but they're not important for now.
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And remember.Electronics is the future,learn some today.
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