Beginner Electronics - Beginner Electronics – 24 – Integrated Circuits: 555 Timer

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Beginner Electronics – 24 – Integrated Circuits: 555 Timer

what is going on everyone my name is Kota moore and welcome back to electronics episode 24 in this episode we will be covering integrated circuits

and specifically the 555 timer integrated circuit today and I'm very very very excited to be making this episode because today we are finished with all the boring stuff that we just

learned in the previous tutorials we are taking our very first steps into the things that we're going to need to really really know in making an 8-bit computer this is going to be really

exciting so let's get to it now in IC is short for an integrated circuit and it is a circuit that is packaged on or essentially placed within a very very small piece of semiconductive material

or more basically it is a circuit that is made to be very very small now most I sees that you're going to see look either like this or this here now this first I see that you can see here

is an integrated circuit that has zip packaging or dual inline package ngey IP basically it has pins as you can see here that can be easily accessed and placed into a breadboard for example and

the other common type of IC packaging is called surface mount packaging and that is what you can see right here now these are both the exact same IC just there in different packaging and surface mount

packages like this chip right here are usually used more at the production level for mass-produced circuits rather than prototyping because the pins are so much smaller now because of this any IC

that you purchase for the most part will likely want to be a dual inline package IC or it should look something like this with the longer pins that you're able to easily access input into a breadboard

now ICS have many different functions of course they all do something completely different it will be discussing many of them as we go on with this tutorial series

but one of the most popular ICS that you should first learn about in electronics is probably going to be the 5 5 5 timer IC or the triple 5 timer and this IC has been used for many many years and it has

many different uses but today we will be using it to create an oscillating circuit like we did in the previous video however it'll be much more controllable accurate and stable

compared to the circuit that we built last time now the triple 5 timer IC which I have right here as well as the previous two ICS that you just saw has eight pins in this example you can see

four of them on front here and there are also for them on the other side of this now whenever you are working with an IC the pins are numbered and they are numbered

counterclockwise starting at the upper left pin and you can tell what pin is the upper left because every IC will usually have a small little indentation like this one does right here at the

upper left so we know that this is pin number one or if that's not the case it'll have a little indentation on the top part right here which you can kind of see right there and that indicates

the top of the chip so that we know this pin should be number one as well and this IC just happens to have both of those they both example and the little dot here but some ICS may only have one

of those they all look a little bit different and like I said the pins on an IC are numbered counterclockwise so in the case of a five five five timer pin one is connected to ground or

essentially the negative terminal of your battery and pin eight is called VCC here or essentially where you're going to connect the positive terminal of your battery to now in the case of most other

ICS the bottom-left pin will usually be your ground pin while the upper right pin will usually be your VCC or your positive terminal pin but of course all ICS are different so it's very important

to have the data sheet for the IC that you are working with in front you to know what all the pins mean and what they should be connected to for example if you accidentally connect VCC and

ground backwards you could badly damage the IC chip so I know the names of each one of these pins just because I looked at the data sheet for the 555 timer now I'm going to begin by drawing out the

circuit building it and I'm seeing it work and then I will go through a very detailed explanation of how everything works in the triple v timer now we are going to use the triple v timer today

and what is called a stable mode and the triple v timer can go in three modes you have a stable monostable and then i'm going to write the other one down here there's also by stable mode as well so

we are going to be making a circuit that runs the triple v timer in a stable mode meaning that the output pin will be a constant cycle so essentially from the output pin here that is where our

oscillation is going to be it's going to be off for a few seconds it'll turn on for a few seconds off again on again off again on again in the square wave pattern and of course

it's going to do that automatically just like the circuit we built in the last video now it can also be run in what is called mono stable mode where some sort of trigger like a button press will

cause the output to go on and then off for a set amount of time and there is also by stable mode but we won't be talking about monostable or by a stable mode at this moment we are just going to

make a circuit that closely resembles the circuit that we had in the last video but of course is going to be much better and more accurate and stable so let me begin by drawing the schematic

diagram here first we're going to start out with our battery this is of course the positive terminal of the battery and that will be hooked up to VCC and from the positive terminal of the battery we

will have a resistor here and I'll give you the values of these resistors in just a few moments and that resistor will be connected to pin number seven or the discharge pin of the IC and from

there after that resistor we will have another resistor hooked up here and this resistor will be connected to that's the rush hold pin pin number six of the five five five timer and I should actually

probably label this IC that way we know what it is the five five five timer and from here we will actually have this go to the trigger pin pin number two of the IC and

we will also have it go to a capacitor right here and that capacitor the other side will just be connected to ground I'm just going to write GND that way I don't have to make a connection all the

way up to the negative terminal of the battery great now the control voltage pin number five is just going to have a capacitor on it and that capacitor will be connected to ground as well the reset

pin pin number four is going to be connected directly to the positive terminal of the battery or VCC again instead of making a wire connection up there I'm just going to write VCC so

that we know where it goes ground will of course be connected to the negative terminal of the battery here and then we will have our output pin which actually has our oscillating signal and we'll

connect that to a different circuit like a blinking light or something so actually let's have this output pin jump over this wire and we can just lead this on up to I don't know say a resistor

here and that resistor will just lead to an LED so that we can get a blinking light and the LED will be connected to the negative terminal of the battery so I know this is a really

messy schematic symbol but this is what we want to build on our breadboard now this capacitor right here connected to control voltage I make that a zero point one nano farad capacitor really this can

be any value capacitor but you probably just want a very small value so don't worry too much about the actual value of this one now for this other capacitor here as you can see I drew an

electrolytic symbol here because I want a slightly larger value you can use a value such as a 100 micro farad capacitor in my case I'm going to be using a 470 micro farad capacitor and

essentially the larger the capacitance value right here the lower your frequency is going to be or essentially your light is going to blink slower with the larger the capacitance that you have

so you can experiment around and try different values for this capacitor here if you would like and then the two resistors will actually will make them 4.7 K ohm resistors so this one will

also be a 4.7 K ohm resistor as well again you don't have to use exact values it can be a bit different of course and I should probably mention that I will be using a nine volt power source which

means that your resistor over here will have to be of a large enough value that where your LED won't burn out so in my case I'm just going to approximate I'm just going to use a 1 kilo ohm resistor

here because I'm just assuming that that's not going to make my LED burn out or anything it should resist enough electricity for that all to work so there we go that is what we will be

using to make our circuit let's build it run it and then we will go into full-on in-depth explanation about it so I'm not going to go through and build the entire circuit on camera you should be able to

see most of the connections here all I have to do is add two more resistors in this circuit will be completed along with our schematic that we made as you can see I have my 470 micro farad

capacitor my point 1 nano farad capacitor like I said this one isn't required but you probably want to have it it's good practice to do so I have my triple 5 timer chip and if i zoom into

it a bit more here you should be able to slightly see on the top here there's a little indent and I'm sorry that it's hard to see on the camera but that is how I know it's the top of the chip and

that this pin is the upper-left pin or pin number one so it's important that you make sure that your triple 5 timer chip is oriented the proper direction and the same goes for

everything like the LED make sure that sucked up correctly I have my resistor here everything should be hooked up properly let me just go ahead and I'm going to

take my two four point seven kilo ohm resistors one is going to go from pin eight to pin seven and you want to make sure that you don't have any weird connections touching each other

accidentally and the next is going to go from pin seven to pin number six so let me put that in right now as well so my circuit looks very very message especially up here that's probably why

you're going to want to spread out all your connections a bit more so who has time for that I certainly don't so let's actually hook up the power and get this thing running so once I connect

to the 9-volt battery the LED instantly turns on and then after a couple of seconds it should turn off breath and it'll turn back on as you can see and it's going to continue to blink and

later on in this video I show you how to calculate the frequency of how this light is turning on and off but anyways this is the circuit in action so let's go into an explanation of all of this

now this is probably going to be the biggest explanation that I have ever done this far in this series there is a lot of stuff that I have to explain here and there's also a lot of things within

the triple five timer that we haven't talked about yet that I also have to explain now it can be a really tricky thing to understand so if you get really really confused don't worry about it

follow along with the series maybe come back to this video it can be quite tough to understand and I'm going to try my best to explain it the best I possibly can now there's a thing within the

triple five timer called a flip-flop I've drawn it so that it looks kind of like a switch but it's really not a physical switch in the triple five timer but I just drew it that way because it's

easier to show how it functions so there isn't an actual physical switch within here second of all we see that there are these two little triangle things in here and those two triangle things are called

comparators right here we have not talked about comparators yet so let's do a brief little introduction into what the comparators are going to be doing within the triple five timer so we have

two inputs the top is called the V plus input the bottom is called the V minus input and then coming out of a tip of the triangle we have the output signal and actually before I continue on with

this explanation I have to explain two words that I'm going to be used throughout the remainder of this series I'm going to be using the words hi and I'm also going to be using the word lo

quite a bit whenever I say hi it means that there is voltage we are connected to the positive rail it's sending out voltage on this wire or this is essentially equivalent to the number one

meaning we do have voltage whenever I use the word lo I mean we don't have any voltage or we're connected to ground zero volts in fact and this is also equivalent to the number zero you'll see

that a lot so hi we are sending out voltage on whatever wire we're talking about low means we are not sending out voltage instead we are connected to ground on that wire those are two very

important words that we're going to be using throughout the remainder of this series hi is voltage low is no voltage or ground okay back to comparators right here now

I've written down exactly what happens here in these two lines so what we are saying is that the output signal here the output will be high or it will connect to VCC to positive voltage and

it will send out positive voltage only if the V Plus input is greater than the V minus input so if we have more voltage coming into the plus input than we do coming into the minus input then the

output will become high and it will send out positive voltage for us however and I also have this written down next to it over here the output will be low or connected to ground if the V Plus input

is less than to the minus input so if the voltage coming into the plus input is less than the voltage coming into the minus input the output will be low connect to ground that is what a

comparator does and I'm going to leave this text on the screen right up here that way that you can refer to it as I am explaining things because it is a very key part of the triple v timer of

course now that those basic explanations are out of the way let's get to how this is working so the first thing that we are going to notice is that the VCC and ground pins are connected by three

resistors in series here and these three resistors actually split up our input voltage so go to comparator a here is going to be one third of our supply by voltage one third of our VCC while

this wire going down to comparator B to the minus input is going to be two thirds of our input voltage two-thirds of our VCC now I used a 9-volt battery so instead of writing that I'm just

going to say that constantly we are getting to the plus input of this comparator three volts because that is one third of my nine volt supply into the minus input of the B comparator we

are getting six volts because that is two thirds of my power supply and that's pretty much going to stay constant we will always be comparing something to three volts here in something to six

volts down here now really the only tough part that I have to explain is this control voltage pin here which as you can see is also connected to this minus input basically don't worry about

this control voltage pin for now because all in all it's pretty much just connected to ground constantly and the only reason that we have this capacitor here is just to smooth out the input

that way we have a nice smooth voltage going into this comparator that's the only reason we have this capacitor here and the control voltage pin also helps set the sensitivity of the triple v

timer but again for this basic explanation and because we just have this connected to ground essentially imagine that this control voltage pin is doing nothing so we're just comparing

something to six volts here and trust me that isn't going to hurt my explanation when we first start up this triple v timer what happens well we have from the VCC pin traveling through this resistor

here and electricity instead of traveling down here it has an easier path to travel it will actually choose to go through the discharge pin instead and go directly to ground because

through the flip-flop here that switch is connected to ground to begin with so electricity is basically just going to go from the positive to ground and it's just going to skip this entire part

right here because it's an easier path so if that is happening then we basically just have a ground signal traveling over on to the trigger input pin so we have going to this negative

input of the a comparator zero volts because it's connected to ground so let's look at our comparator settings up here what will this comparator output well the

plus input is greater than the v- input three volts is greater than zero volts that means that the output of the comparator in letter a that means that the output of comparator a will be high

or it will send out voltage and whenever we get a high output out of comparator a the switches of the flip-flop are going to switch to their down position so this switch right here is going to move down

here to a no connection while this switch right here is going to move down to positive power instead of ground so we flip the switches downward in this flip-flop because the comparator letter

a is sending out a highest signal okay so when we start up the triple five timer essentially what happens is our output is almost instantly connected to positive power our output goes high so

our output is high so what happens after all of this takes place well let's go back to the start again we have coming from positive power VCC through a resistor except remember that the

flip-flop is in the down state right now so electricity isn't going to travel through the discharged pin any more because it is no longer connected to ground it's connected to nothing so it

has nowhere to travel to so instead it'll continue to travel through this resistor here and it will begin to charge up this capacitor right here so for a certain amount of time as this

capacitor is charging up we will essentially have going through this threshold pin to the positive input of the D comparator zero volts and then after maybe a very short amount of time

depending upon the capacitor and resistor values it will climb up to one volt and then after a little bit more time it'll climb up to maybe two volts and then three volts and because the V

Plus input is less than the V minus input now because remember V minus is at six volts two-thirds of our supply voltage our output of this comparator stays low so the switches aren't going

to switch to up because the output is low it's not activating the flip-flop so our output is essentially stuck at the high output for so long and it's going to be stuck there until the input of our

comparator the plus put reaches just over six volts so for example purposes I'm going to write seven volts but in reality it's just going to be a tiny tiny amount over six

volts now the second that that happens comparator B is going to output a high signal because now v+ is greater than v – so since we have a high signal going to the switch-up portion of our

flip-flop these switches that are in the down position are going to flip back to their up position again so let me go ahead and just remove all these lines here that I have drawn now these

switches are back in their up position because we had a high signal come to the switch up input so because that all took time to happen because this capacitor was charging up to get to that voltage

greater than 6 volt our output stayed high at VCC for some amount of time and it just switched back to its ground connection again so now our output has gone low so now what's going to happen

again let's begin at the beginning and see what is happening now from VCC we have power going through this resistor but now it has that easy path again it will go through the discharge pin to

ground because that's an easier path for it to take to travel because our capacitor is about two-thirds of the way charged up it's at about 6 volts it's going to begin to discharge and it will

start to discharge basically through the trigger input right here through the minus sign of this a comparator right here so it's going to begin at 6 volts well in this case v+ is less than v – so

our comparator is going to output a low signal so it's not going to make the switches go down just yet but slowly over time the capacitor is going to discharge it will go down to 5 volts

it'll slowly go down to 4 volts and once it gets barely below 3 volts again for example purposes I'm just going to write 2 volts to make it simple once it gets below 3 volts over that short amount of

time comparator a is going to output a high signal because now the plus is greater than V minus again so we're less than one-third of our supply voltage it's going to make the switches flip to

their down position once more so our output was at ground or low for a little bit of time now it just switched back to high again in this cycle is going to repeat so at this

point in our circuit the discharge pin is now in the down position connected to nothing so it'll begin to recharge this capacitor right here and it will charge it until it's just over two thirds of

our supply voltage again and when that happens this comparator will make the switches go to their up position again and the whole cycle is going to repeat and because this all takes a bit of time

due to the resistors and the charging of the capacitor which I'm going to explain in just a few moments our output stays connected to ground or low for some amount of time and then it stays

connected to VCC or it stays high for a little bit amount of time and it switches back and forth between that it's an alternating cycle so hopefully that explanation got you through how

this triple v timer worked for us I'm really hoping that I explained it well enough if you have any questions at all leave them down below in the comments I or swimmin oats will try their best to

answer your question try to get you to explain this the best we possibly can so we have just a couple more things to explain first of all reset is constantly connected in our case to VCC basically

whenever a reset goes low so if we were to connect reset to ground it's just going to automatically force the flip-flop to reset to the up position and it'll stay in the up position until

our reset goes high again and it will allow the triple five timer to function again okay so how can we calculate the frequency of our triple five timer well there's a really neat equation that

someone created that we can figure that out with basically we have frequency equal to one point four four divided by and I'm going to call this resistor a right here and resistor B so we have

that divided by resistor a plus two times the resistor amount of B all x and we'll call the capacitance of this capacitor C so we're going to multiply that by the farad capacitance of that

right there so the frequency in the circuit that I built is going to be one point 4 4 divided by both of my resistors were four point seven K ohms so I have four thousand seven hundred

ohms plus two times four thousand seven hundred ohms as well and then all of that is multiplied by my 470 micro farad capacitor so because I had 470 micro farad's and we have to make this in the

fair I'd unit that is equivalent to zero point zero zero zero four seven farads I believe and actually I'm not going to write that F in there just to make it more readable so if I do the calculation

I should have the frequency that my output was oscillating at so when I do calculate that I get my frequency to equal approximately zero point two one seven Hertz which is abbreviated Hz and

that basically means how many times per second is this cycle happening so I had a very very slow oscillation because I used such a big capacitance value so my light wasn't even blinking on and off

once per second it was doing it even slower than that but if we reduced the capacitance value so if this value got lower then our frequency would increase or if these resistance values got lower

than our frequency would increase and it would be faster and faster so you should probably try and experiment around with your resistor and capacitance values there that way you can see all different

frequencies with your triple five timer again I hope I explained this all well enough for you guys any questions leave them down below in the comments this is really fun we are getting into the meat

and potatoes of this 8-bit computer series now we just have to cover a few more basic concepts until we actually get into designing the 8-bit computer thanks for watching everyone and I'll

see you guys in the next video

We learn about integrated circuits, specifically the 555 timer!

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