# Beginner Electronics - Beginner Electronics – 20 – Diodes

## Beginner Electronics

29 Lessons

### Beginner Electronics – 20 – Diodes

what is going on everyone my name is code Moore and welcome back to electronics episode 20 today we will be learning about a very important

electronics component the diode diodes will allow us to properly utilize many other electronics components and can help us when using capacitors in a simple circuit that we're going to build

a little bit later on in this video now we have heard of a diode before LED stands for a light emitting diode so in fact an LED is a type of diode now a diode essentially only allows current to

flow in one specific direction which is why we must connect an LED or any type of diode for that matter in a circuit the proper way around so diodes have an anode and a cathode that must be

connected in the proper order and position within a circuit now for the remainder of this tutorial series and for nearly all electronics work that you're going to find on the internet or

just in general life conventional current flow will be used this is used to help reduce confusion conventional current flow is basically just think of all things electronics going from

positive to negative or from the anode to a cathode so electricity think of electricity traveling from positive to negative whenever we are discussing any type of electronics or electricity flow

or current flow conventional current like I said is used to reduce confusion which is especially important when we're talking about diodes so just think of current and electricity flowing from

positive to negative all right now the schematic symbol for a diode is actually just a simpler version of the schematic symbol for an LED it's this triangle with a line on it and that's the

schematic symbol for a regular diode now there are other types of diodes but for this video we are just going to focus on a regular kind of standard normal diode no the anode is sort of at the base of

this triangle here that's the anode and where this line is drawn right here that is the cathode and it's gonna circle those there now a diode allows current to flow from the anode to the cathode so

it allows current to flow in that direction there however if current begins to try to flow in the opposite direction from the cathode to the anode then the diode is going to do its best

work and it's going to try its hardest to stop this current from flowing any further past the diode so essentially whenever current tries to flow the opposite way in a diode

the diode kind of makes the circuit like an open switch would like there's almost no connection there at least that's what an ideal diode would do except it should allow current to flow regularly from the

anode to the cathode so let's take a look at a very basic schematic involving a diode and we are actually going to start with something very familiar sort of our regular LED basic circuit here so

we're going to take the positive side of the battery there and we're going to wire it up beginning at a resistor and then this resistor is going to go ahead and connect to an LED a light-emitting

diode which sort of has the two arrows coming off of it so we have our LED there and I'm not really going to focus on this type of diode I'm going to focus on a regular diode so that might get a

bit confusing but we have the LED there and then we are also going to have a diode pointing right after the LED connecting up to the negative side of the battery so since the diode is placed

sort of in this configuration current should flow right from the positive terminal of the battery through the LED lighting it up and it'll be able to pass right through the diode to the other end

of the battery because again the diode allows current to flow in this direction towards the line of the diode schematic symbol so this circuit should work just as it would regularly even without this

extra diode here whenever a diode allows current to flow through it in the proper direction this is something called forward and let me write it here forward bias that means the diode is in forward

bias operating mode it's allowing current to flow through okay so let's try something else let's go ahead and remove this extra diode right there okay and instead let's place that diode the

opposite way around and I drew this kind of weird so there we now have our diode placed in the other direction so what's going to happen here well current is going to begin to try to flow through

the resistor through the LED and then it's going to get to this diode here and this diode is going to stop the current from flowing and it's going to act sort of like a switch was open in the LED

isn't going to light out and our circuit is essentially not going to work because the diode does not allow current to flow through in this opposite direction here because we placed it the

other way around now whenever a diode is preventing current from flow this is called reverse bias there that is when the diode is in reverse bias operating mode it won't allow current to flow

through now in a perfect world a diode would work just like this with no problems at all however in the real world diodes do have limits to them all diodes have a voltage limit so if a

diode has a 10 volt voltage limit and you try to pass 20 volts in the wrong direction on the diode then the diode is going to break and there's actually an operating mode sort of like forward bias

and reverse cut bias it's called breakdown mode so whenever you pass too much voltage the opposite way through a diode like this it essentially breaks down and it no longer

is successful at stopping current from flowing the other direction basically you have broken your diode and that's something that you want to avoid doing so it's important to use the properly

rated diode whenever you're doing electronics work also all diodes in real life have a forward voltage or a voltage drop just like an LED or a resistor has for example my LED uses up about 3 volts

so it takes away 3 volts from the rest of the circuit now regular diodes also have a voltage drop so if a diode has a say 2 volt voltage drop then if we just try passing 1.5 volts in the proper

direction then not really anything is going to happen because if there's not enough voltage to power up the diode correctly and there's just not enough power there so in that case you would

need more than 2 volts to pass through the diode and to actually get current to flow through the circuit so in a perfect world a diode would have no forward voltage you can just pass through any

amount of electricity but in the real world diodes do have voltage limits and they do have voltage drops meaning that you need to provide enough voltage for it to actually work now let's get to

what a diode looks like how to place it properly and do some testing on a diode so we can actually see what a diode does in a circuit and we'll also see how we can use a diode with a capacitor now all

diodes of course look a little bit different but one of the most common type or sty of diodes rather will look something like this it looks similar to a resistor

it might have a bit smoother of a body but as you can see here it has a few numbers written on it so we can tell what it is and it has a little stripe at one end a different colored stripe at

one end of a diode here so if we take a look at this the end with a stripe the silver stripe here that is the cathode so this lead right here towards the stripe is called the cathode and the

anode is on the opposite end of the diode so that's how you can tell which end or which lead is the anode and which lead is the cathode on a diode it's by that little stripe right there so it's a

very important to pay attention to what the anode and cathode is on the diode here now I have a very basic circuit setup just in LED and a resistor and what I'm going to do is I'm going to

take this diode and I'm going to connect the striped end or the cathode end into the negative power rail of my breadboard here and I'm going to plug in the anode or the more positive end of the diode

into the resistor to complete the circuit so if I go ahead and do that as you can see the LED lights brightly up so while that's working nice and dandy for now what I'm going to do is I'm

going to take my multimeter here and I'm going to make sure that I can measure voltage and what I'm going to do is I'm going to attach my black multimeter probe to this side of the diode and my

positive multimeter probe to the other side of the diode so we are going to measure the voltage drop or the voltage going across the diode now remember in a perfect world a diode would have zero

volts of voltage drop but of course in the real world here all diodes have some type of voltage drop voltage that it takes away from the circuit and as you can see this diode is drawing about 0.7

3 5 volts as its voltage drop so that is how many volts that it's taking away from our circuit which isn't too bad because hey our LED is still lighting up that is fine and just out of curiosity

let's just take a look and see how much voltage my LED here is taking up in the circuit so let me attach my probes to the LED instead like so and my LED is drawing about 3.2

volts as a voltage drop that's how much voltage that my LED is using alright so let me turn off my multimeter and let me unplug these multimeter probes here now let's take a look at what happens if we

remove the diode and place the diode in the opposite direction so I'm going to attach the cathode the end with the stripe to the resistor instead this time and the other end to the negative power

rail on my breadboard now you'll notice how the LEDs slightly lights up there that's only because my two fingers are touching the leads but if I completely let go of it the LED is 100% turned off

the diode is doing its job and it's not allowing any current to flow through the circuit whatsoever which is quite obvious because well our LED is not lighting up anymore so let's go ahead

and try to still measure our voltage so let me go ahead and hook up the probes once more to the diode and turn this on to voltage reading on my multimeter here now my diode is drawing about six point

seven volts across it which is much larger than the less than one volt that it was drawing earlier so the voltage going across this diode is much much more because it's now in reverse bias

operating mode it's not allowing current to flow so if we take a look at the voltage going across the LED now and we do that then we will see that the voltage going across the LED is in the

millivolts range it's reading well it's quite sporadic right now but it's about I'd say 200 millivolts running across the LED which is nowhere near 3 volts that it was reading earlier so that

diode definitely had an effect on the circuit voltage wise but it is doing its job and it's preventing the LED from turning on so let me take my multimeter here and I'm going to make sure that I

can measure amperage so I'm going to move my red probe to the 10 amps lot into my multimeter this way we are able to measure amps and before we do this to remember that measuring amps is much

different than measuring voltage we have to make sure that the multimeter becomes a part of the circus so I'm going to disconnect my diode from the resistor there and just put it over here

and to make the multimeter a part of my circuit I'm going to attach one probe to this side of the resistor and the other probe to this side of the diode so it completes the circuit for us I'll go

ahead and turn my multimeter into amp reading mode and as you can see going through this circuit right now is zero amps now in reality there is probably a very tiny amount of current going

through the circuit but not enough to do anything really to our LED or turn anything on so we're just going to go by what the multimeter says and it says that the diode is doing its job there is

no current going through this circuit great let's try the same thing except let's reverse the diode back around to the proper position so now the diode should be if I can get it plugged in

here the diode is now in the proper orientation so if I connect up my multimeter to the diode we can see that the LED lights up again because it's in the proper position it's in forward bias

operating mode now and there is current running through our circuit about point 0 to 4 amps so the diode is now allowing current to flow because it's in the right direction so hopefully that was a

nice easy way to visualize exactly what our diode does within our circuit here now before I end today's video let's make it a really quick circuit involving a capacitor and a diode alright so here

I have a fairly simple circuit involving a diode capacitor LED and a resistor and the schematic for that is on the screen right now now this is a 1000 micro farad capacitor that I'm using but you can

experiment with different values of capacitance now first things first why do we need this diode here well technically we don't need a diode there technically we can just took both the

terminals of the capacitor and the resistor right up to the positive power line and it would work just the same way however having this diode here is called a protection diode so basically if we

hook up the power incorrectly and we accidentally reverse the polarity of our power rails this circuit won't get damaged the LED won't get damaged of course it won't work because the power

is connected the wrong way but this diode prevents us from accidentally damaging our search if the power reverses polarity so you could technically just use a plain old

wire in place of the diode there but since this is a video on diodes we're going to use a diode okay so let me go ahead and connect the power and as you can see the LED lights up as we would

expect but if I disconnect the power the LED stays lit and slowly dims down so let me connect it again and then disconnect it and the LED slowly begins to dim and this is of course because of

this capacitor right here as we plug the circuit in it both powers the LED and it also begins to charge up the capacitor so it eventually becomes almost fully charged so that way when we disconnect

the power this capacitor is able to drive current through this circuit because of the potential difference within the capacitor that we talked about in the last video now I'm going to

take this 1000 micro farad capacitor out and instead I'm going to replace it with a 100 micro farad capacitor so let me plug this right into the circuit in the proper orientation because

electrolytic capacitors have to be oriented in the proper way of course so if I put that in the breadboard there and I now connect the power once more the LED lights up but if I disconnect it

the LED still dims down but it's much much faster because this has a lower capacitance rating so it can't keep the LED on as long as this larger 1000 micro farad capacitor so the larger the

capacitor essentially the more time we are able to keep that LED on and this diode right here protects the circuit from any incorrect powers so instead if I take my power source and I plug the

negative into the power into the positive power rail and if I plug the positive into the negative power rail and let me do that right here as you can see nothing happens to our circuit

because that diode is protecting the circuit from being damaged but if I connect the power of the correct way again everything works as expected thank you guys so much watching I hope

that you guys learned something and I'll see you guys in the next episode

We learn about regular diodes and build a couple of circuits!

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