Beginner Electronics - Beginner Electronics – 18 – Potentiometers and Buttons

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Beginner Electronics

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Beginner Electronics – 18 – Potentiometers and Buttons

what is going on everyone my name is Co Tamar and welcome back to electronics episode 18 in this episode we are briefly going to talk about buttons and

then we're gonna learn what a potentiometer is and how to use them now everyone knows what a button is so I'm only going to talk about these briefly because first of all you should know

what a basic button does and second of all since there are many different types of buttons they're really easy to understand so if you buy a certain type of button just take a quick look at the

datasheet for it and you'll figure out what all the connections do so let's talk about one of the simplest forms of a button like the one I have in front of me here this button has two metal leads

on it as you can see and basically when the button is not being pressed like right now the connections are broken there is no connection between these two metal leads right here however when I do

press the button so if I press the top of this button like here however long I hold this button down so as long as that red piece is pushed down then these two metal leads will be connected together

and the circuit would be connected if you had wires connected to these two metal leads right here so that's essentially the simplest form of a button you press it and the connections

get made if you release it then the connections get broken now buttons come in many many different forms this does the same exact thing just it's in a little different of a form and this here

is a really tiny button it's called a tactile button and I highly recommend that you get a good stock of these types of buttons because they fit perfectly into bread boards and they're perfect

for prototyping they work exactly the same way as the button I just showed you here with the red cap here just first of all they're smaller and will fit in a breadboard and second of all most

tactile buttons have as you can kind of see here let me see if I can get you a better view they have I'll just flip it over they have four metal leads to it so basically

just like switches buttons can have multiple leads in this case two of the leads are kind of one switch so they're disconnected you press the button and they get connected and the other two

leads do the same thing just separately so you can hook up two separate things to this button again there's many different types just like switches but I'm not going to go into deep detail

with them because again you can look those up online really simple and they're not hard to understand at all and there are buttons that do completely different things such as this button

which I've had for quite a while basically the two leads are disconnected however when I press the button so if I press the button once like so and release it then those two metal

leads get connected and they stay connected however when I press the button again so if I pressed it a second time here then those metal leads come disconnected again so basically it's a

toggle button and these can be really useful in some situations as well but throughout this series I'll probably be using just these small little tactile buttons which I highly recommend you get

because they fit perfectly into bread boards so like I said I'm not going to go too far in depth into buttons here but these are going to be some basic schematic symbols that you might see

this first one here is probably going to be the most common schematic symbol and this is what they call a normally open push-button because originally when you're not pressing it the connection is

open or it's off so these two green leads here are essentially those two terminals are those two metal leads that you saw on the first button I showed you in this blue part here represents the

actual button that you would push so this is when the button is not being pushed so when it's not being pushed these two green terminals are not connected in any way obviously it's an

open circuit hence a normally open push button but when you do press the button then this blue bar would move down and it would make contact between the two green leads so then it would be closed

and it would turn on the circuit so that's a normally open push button the second one here is basically the opposite of that this is a normally closed push-button so when the button is

not being pressed as you can see current can flow from the two wire terminals here so current can flow through this blue part and over into the other one so it's a closed circuit there however when

you press the button this blue bar moves down to here and it opens up the connection between the two green terminals here are the two green leads rather and no connection is made so it

would turn off when you press the button and this third one over here is going to be called a double pull push button so just like a switch we have single pole and double pull switches we have single

pole and double pull buttons as well so this is a double pull button basically one set of connections up here is on originally well this one is open or off and when you press the button basically

it switches this blue bar would move now – this connection here so now this set of connections would be on and this set of connections would be off when you press the button now before we talk

about potentiometers I'm going to show you what one looks like now this is a potentiometer here but potentiometers come in many many many different shapes and sizes and forms and everything so

you're going to see a lot of different types of potentiometers but this might be one common one that you see basically it's a little case that has three terminals on it as you can see here are

three connections that we can make and it has a rod coming off of it that you're able to spin left and right if I turn it up like this as you can see we have three terminals and this little

knob that were able to spin left and right so that's one type of potentiometer another type of tenshi ometer that I'm going to be using is this little tiny one here it still has

three leads coming off of it like so except instead of a giant knob it just has a little screw that I'm able to turn with a tiny screwdriver instead but that is another type of potentiometer alright

so I just showed you what a potentiometer looks like it's something that has three metal leads coming off of it and it has some type of knob or screw that you're able to turn but what in the

world do potentiometers actually do well a potentiometer is essentially a variable resistor so regular resistors are able to resist some amount of electricity so you have for instance a

500 ohm resistor a potentiometer though might be able to resist anywhere from two hundred to a thousand ohms in the amount that it resists depends on what position that knob or screw is turned in

on the potentiometer so potentiometers allow you to change the amount of resistance that they have now we saw that potentiometers had three terminals on them and that's represented by these

two blue dots and a green dot down there now this diagram by the way is actually going to represent the inside of a potentiometer what actually happens within a potentiometer so if you were to

go ahead and take a potentiometer apart most likely you will find a layout very similar to what I'm going to describe here and I encourage you guys to look up some videos online of people taking

apart potentiometers so that you can see this even better but to understand how potentiometer works it's easier to figure out how they actually work inside so the first thing that you're going to

notice is that there's something connecting the outer two pins of the potentiometer so as you can see these outer two metal pins of the potentiometer are being connected by

this orange line here now this orange line is not just regular wire that orange line inside of a potentiometer would be some type of resistive material for the sake

of simplicity all say that this orange material that I have drawn in on the diagram here that I'm highlighting that is not wire that is resistive material basically stuff that would make up a

resistor it resists electricity but this green wire in here that as you can see that's just in a circle and is attached to the middle terminal you can say that that's regular wire for this explanation

so we have this outside band of resistive material that will resist electricity and we have this inside band that's just a regular wire and for sake of simplicity we will say that that has

zero resistance so it's just a regular wire now if you were to go ahead and take a multimeter or hook this up into a circuit where you hook a component up to the outer terminals of the potentiometer

so you just hooked something up in between the outer terminals of the potentiometer then no matter what the knob or screw is turned to you're going to get a solid resistance value you're

just going to get essentially a resistor that has a value of whatever the resistance of this orange material is in the potentiometer it's not going to change at all no matter what position

that the knob or screw is turned in so technically you can use the potentiometer as a giant resistor regularly but obviously we don't want to use potentiometers that way there's this

middle terminal which actually does all the magic for us and there's also something called a wiper which I will draw in as this little orange triangle right here that orange triangle is

called the wiper and this wiper is essentially moved about or moved around in a circle depending upon as you turn the knob or as you turn the screw so as you turn the screw or the knob that

wiper there is going to move along this little green track and it will keep in contact with that orange resistive material so basically this wiper contacts the resistive material at some

point and it's also contacting essentially just the middle terminal of this potentiometer since that's just regular wire so it's giving us a connection to somewhere along this

resistive track along this resistive material here now how in the world is that useful well let's say that we turn the knob so that the wiper is in this position right here now if we were to

hook something up to this outer terminal here in this middle terminal so we some device and power of course then electricity is going to have to travel through all of this resistive material

so it's going to be resisted just like a resistor until it finds the wiper here where it's just going to be able to jump across here and jump right on out the middle terminal so it has that much

resistance to it but if we were to instead connect something to the left outer terminal in the middle terminal here and we connected something then electricity would only have to travel

through this much resistive material and it then it would find the wiper and go right across to the middle terminal again so as you can see this distance right here or rather this distance

covered in resistive material here that's much shorter than this gigantic distance going from the other way around so this way when we connected it to this outer terminal here would provide way

more resistance than if we went with this terminal because it has further to travel along this resistive material so really to make a potentiometer work you only need to connect two of the

terminals itself but of course all three terminals can be helpful in some cases so that's how a potentiometer works it basically creates the shorter path across this resistive material here that

way you can change the overall resistance of this potentiometer so let's quickly go over the schematic symbol and design a quick circuit that we can actually build and test using a

potentiometer the schematic symbol for a potentiometer is pretty simple it's essentially just the same schematic symbol for a resistor because in reality that's what a potentiometer does except

it has a little arrow pointing up into the resistor like that and another wire leading into that arrow so at the two ends of this schematic symbol here in here those represent the two outer pins

of the potentiometer while this arrow sort of line here or this arrow terminal represents the center terminal of a potentiometer or essentially the connection to that little wiper that

moves when you turn the knob so to begin we're going to need a battery so we're going to draw in our battery schematic symbol like so and from the positive terminal we are going to go right into

an LED here so we're going to have an LED that will light up there's our LED and instead of using a resistor like we did in our very first circuit we are instead going to use a

potentiometer so we are going to draw in what looks like a resisting symbol so there's our is your symbol here except we are going to draw that arrow to indicate that it is

instead a potentiometer and we're going to connect this arrow part over to the other terminal of the battery and we can just leave this part of the potentiometer symbol blank because we

only need to use two of the terminals on a potentiometer for this so this is it this is our schematic for the circuit that we're going to build so this is just like our first circuit except

instead of using a regular resistor we're going to use a potentiometer so we are attaching the wiper or the center terminal of the potentiometer and one of the outer terminals to the LED to make a

circuit this way that when we turn the knob the resistance value is going to change and since we're going to change the resistance by turning the knob then our LEDs should get dimmer and brighter

as we turn it so let's get to building this so before I go and build that circuit I'm gonna see what values I can measure on my potentiometer without any power at all so I'm just going to have

my multimeter here and I'm going to turn that into the resistance measuring so that I'm measuring in ohms and I have here a potentiometer now here you can see it says 1m that means it's a 1 mega

ohm potentiometer but if we didn't know that all we have to do is touch two leads to the two outer leads of this potentiometer I'm kind of doing this in an enclosed space here but as you can

see I get one point zero one five mega ohms which is really close to 1 mega ohm so that's pretty much spot-on alright now remember these two outer pins aren't going to change no matter what we do to

that Center or I'm sorry to debt a knob or screw I'm gonna have to hold this potentiometer a little bit out of view as I measure this but I'm going to attach one probe to the center terminal

and one probe to the far left terminal of my potentiometer like so and I'm gonna hold it there there's my probes and I'm gonna turn this thing all the way to the left and

as you can see I'm getting a reading of about 2 ohms that's nowhere near one mega ohm that's really small that's almost no resistance there however once I start turning this potentiometer to

the right you will slowly see on my meter that the resistance value is going to begin to increase so if I turn it a bit more like that and let it settle out now we're at about point four mega ohms

so that's really much larger if I turn it all the way to the right now we're back at that full resistance value of this potentiometer which is 1 mega ohm so if I go a bit back to the

left maybe here's all the way left I'll turn it a little bit to the right now we get a value of let's see what it gives us only 2.1 ohms if we go a little bit more then we'll see if this reads

correctly now we're at 10 kilo ohms so as you can see this resistor chain or I'm sorry this potentiometer changes quite rapidly with how we turn the knob and there's some reasons why that

happened and not all potentiometers are that responsive but I'm not going to get into that in this video anyways that's how we can measure the values of our potentiometer so let's go ahead and

build that circuit now all right so our circuit is really simple I'm going to connect the longer leg of the LED to the positive power rail of my breadboard here like so and into one of the rows

and then I'm going to attach the right leg of my potentiometer so the far right terminal to that LED I don't know if you can see that there I'm going to push it in so that it's inside of my breadboard

and then I'm going to attach the middle terminal of this potentiometer so this wire is leading to the middle terminal of the potentiometer and I'm going to connect that over to ground here let me

go ahead and do that so that is our completed circuit again is really simple we have our potentiometer connected to the middle terminal is ground and connected to the far right terminal is

our LED now it's important that you know what terminal that you're connecting to so if I'm looking at the potentiometer in this way and I'm connected to the far right terminal then that means if I turn

the screw all the way to the left I will have a higher resistance value and if I turn it to the right then I would have a smaller resistance value now if you did this in the opposite way so if you

connected your led to the far left terminal of the potentiometer then turning it left will give you a smaller resistance value and turning it all the way to the right or to the right will

give you a larger resistance value and that's important because we don't want to burn out our LED which by the way this is a warning you might burn out your LED if you don't do this slowly and

carefully and if you have a small value you potentiometer so in my case I'm hooked up to the far right terminal so I'm going to go ahead and turn this screw to the left or counterclockwise

and I'm going to do that as far left as I can that way my LED shouldn't burn out because we have the highest possible resistance value that we can with this potentiometer all right so I've actually

gone ahead and hooked up the power and I've changed out my potentiometer for this bigger one just because it's easier to turn it's in the same configuration my far right terminal in the middle

terminal and I've just attached it via wires now it's turned all the way to the left right now so it's at its maximum resistance which is 1 mega ohm which is why the led doesn't seem lit up at all

because it's too much resisted but if I slowly and the keyword is slowly turn this to the right then we should begin to see at some point an increase in the brightness of this LED so if I continue

turning this to the right you can see that it's beginning to light up and there we go and if I turn it a bit more now it's really bright and I can turn it back down and adjust it and it's very

touchy because this is such a high resistance value of potentiometer but if I had a more proper one then it might be a bit slower and easier to control but nonetheless I can control the brightness

of this LED and that is how you can use potentiometers they're really cool you can do so many things with them and we will be using them in some future projects thanks for watching everyone

and I'll see you guys in the next episode

We learn the basics of potentiometers and talk about buttons!

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