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00:00:00

hello, this is the third part of a simple and

00:00:02

understandable electronics course, today

00:00:04

we are talking about measuring the operation of a transistor and

00:00:06

variable resistors and we will put together

00:00:08

several interesting projects, don’t forget

00:00:10

to watch the first parts, subscribe, like

00:00:13

and, as usual, I wish you a

00:00:16

pleasant viewing,

00:00:20

let’s talk to you about how to

00:00:21

directly measure

00:00:23

basic electrical quantities we we

00:00:26

know that in electronics there is

00:00:28

voltage, current and resistance, and

00:00:32

they are measured respectively in

00:00:34

some units: voltage in volts,

00:00:37

current in amperes, resistance in ohms,

00:00:40

respectively, devices that measure

00:00:43

these quantities are simply called from the

00:00:47

value itself with the prefix meter, that is, volts,

00:00:50

and a voltmeter measures amperes and ammeters

00:00:53

oh we are a meter and so on, perhaps you

00:00:57

remember from lessons these interesting

00:00:59

measuring instruments, pointer

00:01:02

voltmeter and ammeter and meters that

00:01:05

you may have used, these are

00:01:07

analog measuring instruments, they

00:01:09

measure analog signals and transmit

00:01:13

them also in analog form, what is an

00:01:15

analog signal, this is a signal that

00:01:17

does not change constantly, that is, if we

00:01:20

imagine that our axis is

00:01:23

5 volts, here we have 0 volts passing through, then the

00:01:28

analog signal is smoothly inconstant all the time

00:01:30

and smoothly changing,

00:01:32

accordingly, these devices, depending

00:01:36

on how much the signal goes down or

00:01:38

up, changed the position of their arrows

00:01:41

depending on what the signal we measured here

00:01:44

was all tied purely to analog

00:01:46

electronics, but the analog

00:01:50

device was replaced by digital digital

00:01:52

electronics,

00:01:53

here the same analog signal

00:01:56

is converted into a digital signal, that is,

00:01:59

if there is some kind of floating

00:02:03

analog signal, it will be encoded

00:02:06

directly in the form zeros and

00:02:08

ones are transmitted to some kind of

00:02:11

processing device and,

00:02:12

accordingly, output in digital

00:02:15

form. Of course, such measuring

00:02:18

instruments are much more accurate; you

00:02:20

can accurately see the readings; they are

00:02:23

subjective, focusing only on

00:02:25

the arrow if we know what is available from non-

00:02:28

devices that measure individual

00:02:30

electrical characteristics then

00:02:32

today we will get acquainted with a

00:02:34

device that can measure

00:02:36

all these electrical quantities at once and it’s

00:02:38

called it, you can draw an

00:02:42

analogy with multifruit juice, you probably

00:02:44

know a juice in which we can

00:02:46

mix many different fruits together, and so

00:02:50

here, too, many electrical

00:02:51

characteristics are mixed in one device

00:02:54

which can measure them and it’s called a

00:02:57

multimeter or multimeter, I

00:03:00

pronounce the accent on the letter and since I think

00:03:03

this word in English is more

00:03:06

mannered from where it actually came to us,

00:03:08

but you can come across the

00:03:10

pronunciation multimeter and so let me

00:03:13

show you how to use it and produce the

00:03:16

most simple measurements of your

00:03:18

electrical circuits or measure

00:03:22

the characteristics of electronic components

00:03:24

with a multimeter and of course there are different

00:03:26

types, but they all have some

00:03:28

basic elements in common; standard

00:03:32

multimeter models have this rotating

00:03:36

switch and,

00:03:38

accordingly, sockets for connecting

00:03:40

probes, but let's connect them first,

00:03:44

if we look carefully we will see

00:03:46

that here are 3 sockets

00:03:48

black socket com this is the output for

00:03:51

connecting minus and here the

00:03:53

grounding icon is drawn like this the next two

00:03:56

outputs

00:03:57

differ only in current

00:03:59

look at the middle pin it says

00:04:02

volts and minds and milliamps and the leftmost

00:04:07

pin it says 10 amperes

00:04:09

if we want to measure the current value is up to

00:04:12

10 amperes, then accordingly we connect

00:04:15

to this pin; in all other

00:04:17

situations, the middle pin and the

00:04:20

far right one will be useful, so

00:04:22

we’ll connect to them like

00:04:24

this, respectively, now we’ll turn on the multimeter

00:04:27

in the off position; to

00:04:30

turn it on, we need to select what exactly we

00:04:33

want to measure with this type of

00:04:35

multimeter it is possible to measure

00:04:37

constant voltage direct current

00:04:41

alternating voltage

00:04:44

resistance in ohms and we have separately introduced

00:04:48

another convenient function for measuring voltage

00:04:50

on batteries, let's look at everything a little bit,

00:04:53

so let's start with constant

00:04:56

voltage, we can see that now

00:04:58

the switch is turned on in the off position

00:05:00

if we move it to this white the

00:05:04

point on which it says 200 m, this

00:05:07

means that we can measure a maximum of

00:05:09

200 millivolts, let's try, I

00:05:13

have, for example, this kind of

00:05:16

Krona battery and

00:05:18

I will now connect two probes to it,

00:05:22

respectively, minus, on this

00:05:23

side we will connect the black probe,

00:05:26

the red probe to the plus, let's see what

00:05:29

the multimeter will show us,

00:05:32

we see the multimeter shows one,

00:05:35

this means that the voltage is greater than

00:05:38

what we have now set here,

00:05:41

let’s try to put two thousand

00:05:43

millivolts, or essentially two volts,

00:05:47

I’ll measure the

00:05:48

same thing again, you see one because

00:05:51

this battery is actually 9 volts,

00:05:53

so I set it to twenty, that is, the

00:05:56

maximum voltage is 20 volts again

00:05:59

according to the measure and

00:06:00

now the multimeter already shows me a

00:06:03

voltage of almost 10 volts, respectively, the

00:06:07

further you move away from the

00:06:10

measurement limits, the readings will no longer be more accurate,

00:06:12

but look here we have

00:06:14

readings up to hundredths, I switch to the

00:06:17

maximum 200 volts I’m already getting

00:06:20

readings up to tenths of nine and eight

00:06:23

volts and it’s written and if it’s at 600, then

00:06:27

look at

00:06:29

just the whole, they show us without a

00:06:33

fractional part on average 8 volts, they

00:06:35

now show and the icon lights up and the

00:06:38

seams, that is, a high voltage of 600 volts,

00:06:41

respectively, if we want to measure

00:06:43

for example, such a

00:06:46

battery, we can again set it to,

00:06:49

for example, 20 volts and

00:06:52

connect with probes like this and

00:06:55

we will see that this battery is now charged

00:06:59

at

00:07:00

3.96 volts, this concerns the measurement of

00:07:04

constant voltage, let’s also

00:07:06

demonstrate to you how you can measure the

00:07:08

voltage of some simple

00:07:10

chain, for example here so now I will

00:07:13

apply power,

00:07:16

the LED lights up and we can

00:07:19

try to measure the voltage in

00:07:21

this circuit, how can we measure it? If I

00:07:25

want to measure the voltage that

00:07:26

comes from the power buses, I can

00:07:28

connect to this and to this leg, that

00:07:31

is, the extreme terminals and I will see that

00:07:33

the voltage I now have 9 volts,

00:07:36

so let's try to

00:07:37

see what the voltage drop across the

00:07:39

resistor is,

00:07:40

I connect the probe to the resistor and I see that I

00:07:43

have now taken over 5-7 volts, and

00:07:46

the LED got the rest,

00:07:48

that is, 32 volts, and accordingly, this way we

00:07:52

can measure

00:07:54

the voltage, please note Please note that

00:07:56

I am connecting the multimeter in parallel to the

00:07:59

elements, that is, in parallel to their

00:08:01

legs, if I want to measure not

00:08:04

the voltage, as now the outflow, I

00:08:07

will need to connect it in series in

00:08:10

a chain, for example, resistors and LEDs,

00:08:13

but let me switch our multimeter to

00:08:17

measure direct current, let

00:08:20

’s set it to 200 milliamps maximum

00:08:22

since we guess that there

00:08:25

should be about 30 milliamps here and

00:08:27

let's try to measure what is needed for this, I

00:08:30

now turn off the power, for example,

00:08:33

this red terminal plus I connect it

00:08:36

all to the multimeter like this, I'll clamp it with my hand and,

00:08:39

accordingly, continue the circuit with another probe, that is,

00:08:42

I returned this blues power bus

00:08:44

+ well, or it

00:08:48

will be convenient for me to do this with this resistor, I connect and

00:08:50

see that now the current flowing in this

00:08:53

circuit is 24 milliamps, and that is, we see that

00:08:57

now I am connected to the circuit

00:08:59

in series and it is very important never

00:09:02

try to measure the current by connecting

00:09:04

in parallel, you cannot measure it, and what if the

00:09:07

current will be too high, you can also

00:09:09

burn your device, now let's try

00:09:12

to measure the resistance for this, I

00:09:14

move the switch

00:09:17

in the dimension o move, that is, these are all

00:09:21

these yellow parts and here we see the first

00:09:24

designation, look,

00:09:26

it says 200, respectively, the maximum

00:09:29

we must understand what it will be 200 m and

00:09:31

here is such a small icon that looks like a

00:09:33

sound, the fact is that many multimeters

00:09:36

have the ability to ring a chain,

00:09:39

what does this mean when I connect two probes

00:09:44

I will hear this signal, it means

00:09:47

that now there is a short circuit

00:09:49

between these two probes or the

00:09:53

resistance is less 200 m, that is,

00:09:55

look where it can come in handy, well,

00:09:59

for example, when checking the integrity of

00:10:01

these wires, I can

00:10:05

connect to our wire from different sides like this and

00:10:08

find out that now it is intact, but if suddenly there

00:10:11

is a break in the wire,

00:10:14

then naturally I won’t hear any sound

00:10:17

then I have a multimeter that

00:10:20

will tell me about this, I will know that there is a break in this circuit,

00:10:24

there is no short circuit, this is how

00:10:27

you can look for various faults or

00:10:30

look where 1. circuit or your board

00:10:33

leads to another point, are they connected

00:10:36

together or not, well, now let's

00:10:38

try to measure the resistance,

00:10:40

for example, of this resistor, I again

00:10:43

start using the selection method, that is, I set it

00:10:46

to 2000, look at the maximum and

00:10:50

try to touch the legs, please

00:10:53

note that it is better not to touch it with your hands

00:10:55

your skin did not participate in

00:10:58

measuring the resistance, now I

00:11:00

connected the probes to the resistor and I see that I have

00:11:03

238 am this resistor, let's

00:11:07

try to measure the resistance of

00:11:09

such a resistor and

00:11:11

see that my multimeter shows

00:11:13

one again for us this means that

00:11:16

we did not meet this limit

00:11:19

measurement limit so we switch the knob to a

00:11:22

resistance greater than 20k means

00:11:25

20000 you'll see if the resistor is included in

00:11:29

this value really look

00:11:31

now we see that this resistor

00:11:33

has a resistance but practically 10 kilo ohms

00:11:36

it turns out to be even 11 this is how you can

00:11:39

measure resistance up to two

00:11:42

million or 2 mega ohms

00:11:45

multimeters work in a similar way,

00:11:48

which perhaps have other

00:11:51

functions, the ability to measure that everything is

00:11:53

usually designed to switch this

00:11:57

knob, or there are also multimeters

00:11:59

that have auto-adjustment of these

00:12:02

limits, that is, you simply use them

00:12:05

as an example of measurements about move and you don’t

00:12:07

need to select this is 2000 or 20000

00:12:10

kilo-ohms, it automatically selects this

00:12:13

limit as the best limit and

00:12:15

displays it on your screen accordingly, but such

00:12:17

multimeters, of course, are a little

00:12:19

more expensive than these standard

00:12:21

options for the first time, this

00:12:23

option is quite enough for you to

00:12:25

diagnose your circuits and

00:12:28

look for any malfunctions

00:12:30

[music]

00:12:34

let's study another new

00:12:37

electronic component called a

00:12:40

potentiometer, if we look at its

00:12:43

symbol, I think it

00:12:46

already reminds you of something, and

00:12:48

of course it resembles an ordinary resistor, look here is

00:12:51

its symbol for an ordinary

00:12:54

resistor, but here at the top it

00:12:56

also has this arrow, so

00:12:59

the potentiometer is an element that

00:13:01

is a variable resistance, that

00:13:04

is, if before you and I knew about

00:13:07

resistors that always have one

00:13:10

resistance, for example 10

00:13:13

kilo-ohms,

00:13:14

then a potentiometer designed for 10

00:13:17

kilo-ohms can change its resistance

00:13:20

thanks to By turning this knob from

00:13:23

0 to, for example, 10 kilo-ohms,

00:13:27

each potentiometer has a certain

00:13:30

limit within which it will work and,

00:13:33

accordingly, this

00:13:35

resistance changes thanks to this

00:13:38

middle pin. To understand how this

00:13:41

happens, let's see what's inside

00:13:43

this potentiometer and inside our

00:13:46

potentiometer you will see several you in

00:13:49

daf handle resistive substance and

00:13:53

rotating rotor why is all this needed let's

00:13:56

imagine right away on some

00:13:58

diagram I connect pin number one and

00:14:01

pin number three like this, let's sign it in

00:14:05

some diagram let's draw it here and

00:14:08

draw the diagram with the lamp, our beloved,

00:14:11

let's see what path the electrons will take

00:14:13

with such a connection, so you

00:14:16

and I, well, let's imagine that this current

00:14:19

came out of the saucer and got to 1 contact,

00:14:22

then we go along this resistive

00:14:24

substance, what does resistive substance mean,

00:14:27

this is a substance that can

00:14:29

resist the flow of electrons and

00:14:32

look, if I come from 1 to 3 points,

00:14:35

then it turns out that I took up all this

00:14:39

resistive substance and only then

00:14:41

came out here, let’s say if our

00:14:43

potentiometer is designed for a resistance of

00:14:46

10 kilo-ohms, then I’ll get these same 10

00:14:49

kilo-ohms, that is, the total resistance and

00:14:51

here’s how If I didn’t rotate this knob, the

00:14:55

resistance wouldn’t change,

00:14:58

why look at the hooks, the

00:15:01

middle contact is connected and there’s a

00:15:04

sliding contact plate connected, it’s

00:15:07

not involved in my circuit as it is now,

00:15:09

so I’ll always get

00:15:11

only the same resistance value of

00:15:14

10 kilo-ohms, now let’s imagine that

00:15:17

We still started to rotate this knob a little,

00:15:20

let’s say someone turned it and

00:15:23

moved it to this position. I want

00:15:30

this resistance to be taken into account in my circuit.

00:15:31

Accordingly, I no longer connect to

00:15:33

contact number 3, but of course I will

00:15:37

connect to contact number two on the middle

00:15:39

edge and who now, if we look at

00:15:42

such a circuit, then our electrons will not go

00:15:46

further along the resistive substance here,

00:15:48

but will curl up just in this place

00:15:52

and

00:15:54

go along our foot here to the

00:15:56

middle terminal and then again come to

00:15:58

the light bulb, respectively, look

00:16:01

how much we took from the total area of

00:16:03

our resistive substance, but I think

00:16:06

20 percent 5 if our potentiometer

00:16:08

is designed for 10 kilo-ohms, then now we

00:16:11

get about two and a half

00:16:12

kilograms, they are 10 at once, respectively,

00:16:16

if I move this foot to the middle

00:16:19

position somewhere here, you turn

00:16:21

the handle, then I will get It’s 5 kilos and so on, you

00:16:25

can also unscrew it here to the

00:16:28

maximum and then we will get the same

00:16:31

10 kilos it’s like this, you and I will get that

00:16:34

our resistance changes

00:16:37

depending on the rotation of this knob,

00:16:39

which makes either more of this

00:16:42

resistive substance or less, everything is

00:16:45

very, very simple, let's try

00:16:48

to work directly with the

00:16:49

electronic components and see

00:16:51

that our resistance really

00:16:53

changes, let's go as usual to the tinker cat,

00:16:56

and I'll also show you how

00:16:58

this happens in real life, and so let's

00:17:01

find the potentiometer in the list of components

00:17:03

is located immediately in the base

00:17:05

components and let's look at its

00:17:09

contacts here, this is terminal number one,

00:17:12

sliding contact and terminal number 2, we

00:17:16

remember that the sliding contact is

00:17:18

just needed to change

00:17:20

the resistance, and let's try to

00:17:22

assemble the simplest chain, for example

00:17:24

with an LED and a

00:17:26

battery you and I have learned how to

00:17:28

use a breadboard and therefore I

00:17:31

would immediately remove it so that you can see

00:17:34

how the connection occurs on the

00:17:36

breadboard and so we place a

00:17:38

potentiometer somewhere next to each other, put an LED and

00:17:42

apply the power bus

00:17:44

voltage 1 2 respectively, this is the

00:17:48

anode of the LED, which means on it you need to

00:17:51

supply plus, then the cathode of the LED,

00:17:54

let's try to connect it with you

00:17:56

to see how the

00:17:58

potentiometer works, so I'll immediately take it and

00:18:01

connect it to the

00:18:03

sliding middle contact here and,

00:18:06

accordingly, we will already have it

00:18:08

supplied through a

00:18:09

variable resistor like this, so

00:18:13

let's see how it goes will work,

00:18:16

we start modeling and immediately see

00:18:18

that they show me that my LED

00:18:20

has burned out. Why, in fact, remember what

00:18:23

I’m saying: if the potentiometer knob is

00:18:25

twisted to the minimum position,

00:18:28

then its resistance is about zero, and

00:18:31

here, of course, a stream of electrons poured

00:18:35

through the zero resistance and burned our

00:18:37

LED is the first thing you have to remember,

00:18:40

if you connect a variable

00:18:42

resistance that can drop

00:18:44

to zero, then of course you need to

00:18:47

add a resistor to the circuit that will protect the

00:18:49

LED in any case, so I

00:18:52

go in, select a resistor and

00:18:55

let's remove this contact while

00:18:57

we turn the resistor and

00:19:00

also connect it to the middle leg

00:19:03

that's it, and now let's connect a resistor to the

00:19:06

cathode,

00:19:09

we'll set remember, we

00:19:11

calculated for our LED and the

00:19:14

crown will set 470 ohms, now we can

00:19:19

start modeling again, look,

00:19:21

the LED is behaving well, that is, it

00:19:24

now likes the flow, the

00:19:27

resistance of the potentiometer is now

00:19:29

0 if I start it increase little by little

00:19:31

we see how the LED

00:19:34

almost immediately went out, look

00:19:36

literally there were a few

00:19:38

moments before let's see what the

00:19:41

resistance is now on this

00:19:43

potentiometer we see here 250 kilo-ohms

00:19:46

well you understand that of course 250 is

00:19:49

too much let's set it to at least

00:19:51

10 again let's start modeling and we see

00:19:55

that now the LED has already been smoothly

00:19:57

added to it, such a small

00:19:59

gap, well, let's try, well,

00:20:03

you see, it completely went out when

00:20:07

we arrived at 10 kilos, 5 kilos, the mind barely

00:20:10

glows and zero, of course, it glows at

00:20:13

normal brightness, that is, in this way

00:20:15

we we see that the potentiometer copes with

00:20:17

its task of changing the resistance

00:20:19

quite well and if we look

00:20:22

at the connection diagram of the potentiometer it

00:20:25

will look something like this, that

00:20:27

is, we took the middle contact and any

00:20:30

of the two, by the way, you can really take

00:20:33

which is the first, which is 3, it doesn’t matter because

00:20:35

that so the resistance will change all the time,

00:20:39

we will change the path in one

00:20:41

direction or the other, the scope of application

00:20:43

of potentiometers is quite

00:20:45

common, usually they are not

00:20:46

installed everywhere where something needs to be

00:20:48

adjusted, something to be adjusted, such as

00:20:51

sound temperature, and so on and so

00:20:53

on with this we will still work with you

00:20:55

and so this is all you needed to

00:20:57

know so far in the initial stages

00:21:00

about what a potentiometer is;

00:21:06

another interesting component that

00:21:09

can change its resistance

00:21:10

is a photoresistor, let's look

00:21:13

at its symbol, we will

00:21:16

again see what we have there is a usual

00:21:18

image of an ordinary resistor, here it is,

00:21:22

all this is entered in a circle and there are

00:21:25

two arrows showing this

00:21:28

resistor, these arrows show

00:21:30

rays of light like an LED, remember

00:21:32

only it is not directed the other way around from

00:21:35

it, it emits light and this

00:21:38

light component receives the words photo this

00:21:41

component is not in vain because its

00:21:43

resistance depends on light and in fact,

00:21:47

if we translate the words of the photo from ancient

00:21:49

languages, then it will be light, you know, for

00:21:54

example, there are photographs, in fact, if this is

00:21:57

translated photography drawing with light,

00:22:00

we will not be able to take a photograph in

00:22:03

complete darkness, the same the same thing here,

00:22:06

light and a resistor are essentially a light resistor,

00:22:10

that is, a resistance that depends on

00:22:12

how much or little

00:22:15

light there is nearby, let's look at this, if there is

00:22:18

little light near the photoresistor, then its

00:22:21

resistance will be very high if

00:22:25

in complete darkness this will be

00:22:27

its maximum resistance and vice versa

00:22:29

if there is a lot of light near the photoresistor, then

00:22:33

its resistance will tend to

00:22:35

zero and we can also use this,

00:22:38

but the most important application that immediately comes to mind is

00:22:40

its use when

00:22:43

we need to detect illumination on

00:22:45

the street and, for example, automatically turn on

00:22:48

the light when it gets dark, let's

00:22:51

try to connect with you too this

00:22:53

component in the team carcade and see

00:22:56

how it actually works, I won’t

00:22:59

remove our old circuit, I’ll just

00:23:01

remove the potentiometer for now like this and

00:23:03

right in the same place I’ll put a

00:23:05

photo

00:23:06

resistor, it’s also in the basic

00:23:09

components, it’s so beautiful and we’ll install it

00:23:12

it’s in these same tracks that everything,

00:23:15

in fact, now the

00:23:18

resistance will be controlled by our

00:23:20

photoresistor, let’s start

00:23:22

modeling and look, if

00:23:24

you click on the photoresistor, we’ll see that you

00:23:27

can change it, change the brightness

00:23:29

around our breadboard either too

00:23:32

much or, on the contrary, light, look

00:23:35

now the value is set to like than but

00:23:38

our LED barely glows,

00:23:42

maybe even doesn’t glow at all, we start

00:23:44

adding light little by little and see how the

00:23:48

brightness of our LED gradually increases,

00:23:51

so we see

00:23:53

that the resistance of the photoresistor really

00:23:56

depends on how much

00:23:59

light comes to it, the main thing to remember here that

00:24:01

the more light, the less it

00:24:04

resists, and in terms of connecting

00:24:06

a photoresistor, we will get

00:24:08

this circuit diagram with a

00:24:12

regular resistor and an LED, everything is the

00:24:15

same, if you exclude a regular resistor from this circuit,

00:24:17

then if the

00:24:20

illumination level is too bright, our LED may

00:24:23

suffer therefore, always if

00:24:25

you connect LEDs, do not forget about

00:24:28

the resistor

00:24:29

[music]

00:24:31

in electronics you can often find

00:24:34

voltage divider circuits, why is this

00:24:36

necessary, for example, you have a 9

00:24:39

volt battery and you want to get from it not 9

00:24:42

volts but two volts, what to do and in

00:24:44

these cases sometimes when you quickly

00:24:46

need to assemble it from a minimum number of

00:24:48

components, resistive

00:24:51

voltage dividers help,

00:24:53

let's see what

00:24:55

such a voltage divider actually looks like and how

00:24:57

it works, in fact,

00:25:00

you can assemble such a divider from any two resistors,

00:25:03

look, we take 2 familiar

00:25:06

resistors and connect them to the

00:25:09

voltage is, for example, 5 volts on one

00:25:12

side and the other, the resistor itself is naturally

00:25:14

connected in series, I’ll replace them

00:25:17

with a symbol to make it

00:25:19

more convenient for us and

00:25:21

look at the midpoint between the two

00:25:24

resistors, the voltage will begin to divide

00:25:28

a little later, I’ll show you using the formulas why

00:25:30

this happens, let’s understand for now how

00:25:32

exactly is it divided, let’s say we have the first

00:25:36

resistor going to 100 and the other resistor is

00:25:39

also going to 100 kΩ, that is, two identical

00:25:41

resistors connected in series

00:25:42

with each other, if we measure the voltage

00:25:45

at the midpoint between the minus and the

00:25:49

midpoint, we will get two and a half volts,

00:25:52

exactly half of of our total

00:25:55

voltage,

00:25:56

let's imagine it like this, there is a

00:25:59

total voltage of 5 volts, the total

00:26:02

resistance we will have two hundred minds if

00:26:05

we draw some such line

00:26:08

mentally the storm and 100 it will divide

00:26:13

our 5 volts exactly in half and therefore you

00:26:16

and I will get two and a half volts each

00:26:18

but if, for example, one of the resistors

00:26:21

becomes equal to twice as much as the

00:26:23

other, that is, for example, 200 and 100 m, then

00:26:27

you must understand that with such a connection scheme, the

00:26:31

other resistor, which will take more of

00:26:34

the voltage, respectively,

00:26:36

that is, now out of 5 volts we

00:26:39

will get 3 3 volts at 200 kΩ and the

00:26:43

second resistor, which is smaller,

00:26:45

will get the third part, that is, 1 and 7

00:26:48

volts, but you and I can see this

00:26:50

if we connect a multimeter and measure

00:26:52

the voltage, how can we use this circuit

00:26:55

usefully, look, for example, we need to

00:26:58

get the voltage dependence with you

00:27:00

depending on the light level, we remember that

00:27:04

we have a photoresistor that can

00:27:06

change its resistance, but if you

00:27:09

connect it instead of a regular resistor to a

00:27:12

voltage divider, then it will begin to

00:27:15

change the voltage. How can we

00:27:17

calculate a specific value

00:27:19

for the voltage dividers if we have

00:27:21

already taken certain ones? mines choice purchased

00:27:24

resistors look at the ohm law the current in the

00:27:28

circuit I remind you remember we had

00:27:30

a triangle by which we calculated and

00:27:33

knew the calculation formulas and so according to the

00:27:37

ohm law the current is equal to the voltage divided by the

00:27:40

resistance if we take and describe the

00:27:44

resistance in our chain then it is already

00:27:46

will consist of resistor number one and

00:27:48

resistors number 2, respectively, so

00:27:51

we get it r1 + r2 since

00:27:55

the resistors are connected in series,

00:27:58

so this is how you and I can find it

00:28:00

perfectly, but to find the voltage, we

00:28:03

must, on the contrary, multiply the current by

00:28:07

the resistance, we

00:28:10

will take the resistance - the one

00:28:11

on which we will actually measure the

00:28:14

voltage drop, remember the

00:28:17

voltage drop is how much voltage this resistor

00:28:19

will take for itself,

00:28:21

if we substitute all this, we

00:28:24

will get the voltage of the divider at exactly

00:28:27

this point if we believe between the ground on the

00:28:30

resistor r2 will be equal to the current

00:28:33

multiplied by this resistance

00:28:36

instead of r2, alas, of course, you substitute a

00:28:39

voltage that is equal to 5 volts, but

00:28:43

let’s try with some

00:28:44

example, it’s clear that we’ve sorted out the letters here

00:28:46

a little, let’s imagine

00:28:50

some specific values, so

00:28:52

let’s imagine that our photoresistor produces

00:28:55

2000 ohms, a regular resistor produces 10

00:28:59

kiloohms voltage we will measure on

00:29:02

exactly the photo resistor, then we substitute

00:29:06

5 volts into that previous formula, this is the total

00:29:09

voltage of our circuit multiplied by the

00:29:12

resistance r2, I hope you remember this is the

00:29:15

2000th now and divide by the total

00:29:18

resistance of the circuit 2 kilo-ohms plus 10

00:29:22

kilo-ohms, that is, two resistors if you

00:29:24

multiply all this and divide then we get

00:29:27

zero point eighty-three volts,

00:29:29

let's try to reduce this brightness a little,

00:29:32

for example, we made a light bulb

00:29:35

or the light became a little darker and now

00:29:38

our resistances are no longer 2000, he is

00:29:41

again thousands, if we substitute

00:29:44

this resistance again, we will see that now the

00:29:46

voltage drop will be already one

00:29:48

point seven tenths of a volt, that is,

00:29:52

our voltage has become a little more, if we

00:29:54

make the light even darker, then we will get, for

00:29:56

example, the same resistance and

00:29:59

then it will be divided exactly in half, and well,

00:30:02

when it gets dark, most of the

00:30:05

voltage will of course be taken over by

00:30:07

the photoresistor, so you and I

00:30:09

we can calculate the voltage that we

00:30:11

want to get on the divider and let's

00:30:14

quickly see how it works in

00:30:16

tinker cadi so I take resistor number

00:30:20

one resistor number two like this in one

00:30:24

track, pay attention that they

00:30:26

are connected together the other day in exactly one

00:30:28

track on one side then plus I’ll

00:30:32

apply a minus to the resistor on the other side and

00:30:37

so that we can see what voltage is here now,

00:30:40

let’s take

00:30:42

a multimeter and measure accordingly

00:30:46

relative to the negative terminal, that

00:30:49

is, like this, and connect the positive terminal

00:30:51

to the middle point where the

00:30:53

actual voltage will be shared with us,

00:30:55

let’s try to look

00:30:58

now I have this resistor 1 kilo, you

00:31:01

this resistor is also one kiloohm,

00:31:03

the voltage that I supply is 9 volts,

00:31:06

we start modeling and see that

00:31:08

the voltage is divided exactly in half, that

00:31:10

is, four and a half volts, everything

00:31:12

works fine, let's try to

00:31:14

make this resistor

00:31:16

take a little more, that is let's set 2

00:31:19

kilo-ohms and see that now he

00:31:22

has taken 6 volts for himself, respectively, increasing

00:31:25

this resistance, we can achieve the

00:31:27

voltage division we need, you

00:31:31

see now 8 and 18 volts and I set

00:31:35

10 kilo-ohms,

00:31:36

respectively, we can also replace

00:31:38

this resistor with a photo resistor by

00:31:41

sending it to the middle point like this

00:31:45

the photoresistor took almost all the voltage

00:31:48

that was when it starts to get

00:31:50

light, we see how gradually

00:31:52

the voltage gradually smoothly

00:31:54

drops to, for example, 3 volts and by the way,

00:31:58

what is useful about the potentiometer that we

00:32:00

recently studied, it can also be a

00:32:03

voltage divider,

00:32:05

see the middle contact, remember, in fact,

00:32:09

this is the middle contact of our divider,

00:32:12

let's connect to it like this,

00:32:16

sliding our contact

00:32:19

on the other two sides, I'll give it

00:32:23

a minus and a plus, that's what we've

00:32:27

got now, essentially, if we

00:32:29

attach a potentiometer in the form of

00:32:31

resistances, we'll see that this is the

00:32:34

first resistor connected to another

00:32:37

resistor is the average. Well,

00:32:40

maybe I’ll even draw it like this,

00:32:43

here it is this first resistor and the

00:32:46

second resistor comes out of the same point, I hope you

00:32:49

can see that in essence this is the circuit of our

00:32:51

voltage divider and thus by

00:32:54

connecting the potentiometer like this we

00:32:57

can use it in

00:32:59

the form an ordinary divider, well, let's

00:33:03

now look at the voltage

00:33:05

at one position of our

00:33:09

potentiometer 0 volts, respectively, the

00:33:12

second resistor took all the resistance for itself

00:33:14

and now we begin to increase it little by little,

00:33:16

which means the left one, so to speak, the

00:33:19

bottom resistor begins to take

00:33:21

more and more and more for itself, now

00:33:23

half of it and at

00:33:25

most it has taken all of it for itself the left side,

00:33:28

accordingly, we don’t measure it,

00:33:29

we get the full 9 volts and vice versa, that

00:33:33

is, we see that now from changing

00:33:35

the resistance it turns out to divide

00:33:37

the voltage, this is very convenient and useful

00:33:40

[music]

00:33:45

let’s introduce you to another

00:33:48

key component of modern

00:33:50

microprocessor electronics, this is of course

00:33:52

transistor, if you look at

00:33:55

what its name consists of, we

00:33:58

will see that this is the formation of the words transfer

00:34:01

and resistor, that is, converter

00:34:04

resistance, here in front of you are several

00:34:06

types of transistors, from

00:34:09

such huge ones to small ones, they all

00:34:11

have certain characteristics, we will

00:34:15

get to know the most common

00:34:17

type of transistors these are bipolar

00:34:19

transistors,

00:34:20

but specifically let's talk about the npn transistor and

00:34:24

immediately look at its

00:34:26

symbol so that we can figure out

00:34:27

why transistors are needed at all, how it

00:34:30

works on the symbol we

00:34:32

see a component with three terminals,

00:34:35

the name of which will need to be

00:34:38

remembered is base is collector is

00:34:43

meter, but right away let's replace them with the

00:34:46

abbreviated name bk, that is,

00:34:49

no one usually writes in full, and our

00:34:52

transistor can be seen with 123 now

00:34:56

replaced by the mitre

00:34:58

base and collector, respectively, with its legs, how to actually

00:35:01

use the transistor, let's

00:35:03

imagine this situation, we

00:35:05

have a fan which needs a

00:35:08

voltage of, for example, 9 volts and

00:35:10

there is some temperature-sensitive circuit,

00:35:14

the circuit can output, say,

00:35:16

a maximum of 1 volt, let’s sign

00:35:20

the fan with 9 volts, a

00:35:22

temperature-sensitive circuit on its two

00:35:24

terminals can output only one

00:35:27

volt, what does it mean to output, well, for example,

00:35:29

when it sees that it has become warm gives out 1

00:35:32

volt, sees that it gets colder 0 volts, that

00:35:35

is, some kind of indicator, so to

00:35:37

speak, a strict indicator, respectively,

00:35:40

we want to make sure that our

00:35:42

temperature-sensitive circuit controls

00:35:45

the fan when it gets hot

00:35:48

so that it turns on, obviously one

00:35:51

volt is not enough to turn on

00:35:53

the fan, and this is exactly where

00:35:55

the transistor will still help if we connect it

00:35:59

to this shooting, look, I connect

00:36:02

the transistor now I’ll explain why exactly

00:36:05

how it’s all connected and connect the

00:36:08

power source, what’s happening here

00:36:11

we have a circuit that produces one volt,

00:36:13

I remind you, and this one volt goes to the

00:36:17

base of the transistor, I hope you can see the minus is

00:36:20

accordingly combined with the minus of the

00:36:22

power supply and connected to the emitter,

00:36:25

the plus goes immediately to the fan and

00:36:29

here the minus right dock already comes out, I

00:36:32

hope it’s also visible, so if we apply a

00:36:36

positive potential to the base of the NPN transistor,

00:36:40

that is, we create a

00:36:43

potential difference between the base and the emitter, the

00:36:46

transistor begins to open that is,

00:36:49

we pass electric current through ourselves

00:36:52

and thus with a small current we can

00:36:55

control a large current, for example from a

00:36:59

battery, which will turn on the

00:37:00

fan itself. I hope you can see that this

00:37:02

circuit closes like this and the fan

00:37:05

actually starts to rotate, as soon

00:37:09

as the voltage disappears, the result

00:37:12

disappears, our transistor essentially closes

00:37:16

is an

00:37:18

infinite resistance, a huge

00:37:21

resistance that the

00:37:22

electrons of the battery cannot overcome and our

00:37:25

fan turns off everything, so

00:37:28

we got the so-called

00:37:30

key mode of operation of the npn transistor,

00:37:33

this can be compared with a regular

00:37:34

switch only in a regular

00:37:36

switch and we press on the switch

00:37:40

so that it closes, yes in the

00:37:43

case of a transistor, we press with our hands and apply a

00:37:46

positive movement, that is, we create

00:37:48

some voltage between the base and the emitter; as

00:37:51

soon as we apply it, the

00:37:54

current from the base to the emitter begins to flow and the

00:37:57

same current begins to flow from the collector

00:37:59

to the emitter, only higher, for example,

00:38:02

from our batteries and this is how our

00:38:04

circuit actually functions, I hope

00:38:07

I explained it clearly, I keep

00:38:09

saying npn transistor what does it actually mean,

00:38:14

npn is an abbreviation for what

00:38:18

our transistor consists of, it

00:38:20

has several areas that can

00:38:23

conduct current or cannot conduct current

00:38:25

through each other n.p. n means

00:38:29

negative-positive

00:38:31

negative what does this mean it means that

00:38:35

we have rp or pn transitions between

00:38:40

the transistor exactly in these and in these

00:38:42

places, roughly speaking, and

00:38:45

we can influence this transition by supplying

00:38:49

positive or negative signals, and the case

00:38:52

with the npn transistor is necessary create a

00:38:55

positive difference in voltage, that

00:38:57

is, apply a plus here, apply

00:39:00

a minus here so that the current flows in this direction, then

00:39:05

you will open access to this

00:39:07

current; accordingly, in the case of PLP

00:39:10

transistors, it’s the other way around; in order for the

00:39:14

current to flow, you need to apply, on the contrary, a

00:39:17

negative voltage or a

00:39:19

negative current, and thus now

00:39:22

let's see that 5

00:39:25

volts begin to flow down and also

00:39:30

pull the voltage along with them, and if you and

00:39:34

I swap the voltages, then our

00:39:37

transistors will naturally both

00:39:39

close, so you can

00:39:41

use both an npn and a pnp

00:39:43

transistor and depending on which one you have you have a

00:39:45

control signal in our case with a

00:39:48

temperature-sensitive circuit, it produced a

00:39:50

positive signal, so I took an npn

00:39:53

transistor, that is, positive is positive,

00:39:56

if it were the other way around, then I would take a pnp

00:39:59

transistor, the characteristics of the transistors,

00:40:02

as usual, you can find by signing

00:40:04

the words datasheet and the name of the transistor, for

00:40:08

example, the datasheet for the npn transistor

00:40:11

2n 3904 looks like this, here

00:40:15

it is told firstly where it has

00:40:18

a collector, where are the bases and where is the emitter,

00:40:20

look there is always a top view and the

00:40:23

transistor on one side where

00:40:24

its name is written and so

00:40:27

on and so on there is such a small

00:40:29

bevel on the other side it is like this semicircular

00:40:32

if we look at the case exactly trio 92

00:40:36

and

00:40:37

accordingly signed one two three and

00:40:40

we see that the first type is collector 2 base

00:40:42

3 and metro everything is very, in principle, clear

00:40:45

and understandable as well as its

00:40:48

main characteristics are voltage

00:40:52

collector base-collector-emitter emitter

00:40:55

base peak various currents and so on and so

00:40:59

on and so on, that is, these are the

00:41:00

characteristics that you actually need to

00:41:02

look at before you want to buy

00:41:05

this or that transistor, since you can, for

00:41:08

example, connect a circuit at 5 volts, you

00:41:10

can use twenty-five volts, or you can use

00:41:13

220 volts, and in different situations you need it

00:41:16

naturally different transistors

00:41:18

are designed for different values, but let's take a

00:41:20

little look at how

00:41:23

a transistor works directly in the circuits,

00:41:25

how to connect it, I suggest recalling the

00:41:27

simplest circuit for connecting an

00:41:29

LED with a limiting

00:41:31

resistor

00:41:32

powered by 9 volts and let's try to

00:41:37

connect

00:41:38

the transistor directly into this circuit; we want to control

00:41:41

the LED, which means I will,

00:41:44

of course, connect it to the circuit in which we have a

00:41:47

large current and a high voltage,

00:41:50

we will control the voltage with much

00:41:52

less, and now when we have nothing between the

00:41:54

base and the emitter,

00:41:56

that is, there is no

00:41:58

voltage, the transistor is essentially closed,

00:42:01

it does not let anything through what current does the LED

00:42:04

not light up? If I apply some voltage to the base,

00:42:07

for example another

00:42:09

completely battery, then the transistor

00:42:12

will open and my LED will start

00:42:14

to light up. Well, in our case, let's

00:42:16

see this voltage is 0.7 volts and the

00:42:20

positive potential, pay

00:42:22

attention, is supplied to the base, here

00:42:26

the negative one is connected from below at the

00:42:28

emitter, as soon as there is a current

00:42:32

flowing like this, a

00:42:35

current of sufficiently

00:42:37

large magnitudes begins to flow and thus we

00:42:40

turn on our LED

00:42:42

if we remove

00:42:46

the voltage from the base, that is, there will be no voltage here,

00:42:48

then accordingly, the LED will

00:42:51

also turn off immediately 9 volts will stop

00:42:53

flowing through the transistor

00:42:55

will be closed again, I hope it’s clear how it

00:42:58

works, the question arises, what if

00:43:00

I have one power source, they are 2, that is,

00:43:03

there we connected a battery and a

00:43:05

small battery, and if there is one

00:43:07

power source, how can you control

00:43:09

the transistor then here everything is just

00:43:12

look, we connect with you put

00:43:15

some high-resistance resistor on the base

00:43:18

a little later in the next video I will show you

00:43:21

how to calculate this resistance so as

00:43:24

not to exceed the current to the base since this is a

00:43:26

very important parameter, but for now you just

00:43:30

need to understand for yourself that the plus that

00:43:33

comes from the battery from here

00:43:36

is sent to this point,

00:43:39

accordingly, so that the LED

00:43:41

also begins to pass through

00:43:43

the resistor plus the current passes, there is only a

00:43:47

miter coming from the bazooka, which means there are

00:43:49

transistors too, it will open and

00:43:51

begin to let in the current, the main thing is not to forget

00:43:54

about this resistance

00:43:57

[music]

00:44:01

in fact, on the basis of such a simple

00:44:04

shooting, you can already assemble an interesting

00:44:06

small device, I call it a

00:44:09

touch or touch sensor,

00:44:11

look if

00:44:15

instead of a resistor under these two

00:44:18

points here and here we connect, for example, a

00:44:22

person’s arms are just a little long like this,

00:44:26

then in essence a person will also

00:44:30

represent himself as some kind of walking

00:44:33

resistor with with its skin resistance and

00:44:36

will begin to transmit positive voltage to itself,

00:44:39

which will get to the base and

00:44:42

open our transistor. Here I

00:44:45

want to demonstrate to you that in

00:44:47

fact, what is the plus of the transistor, it needs a

00:44:50

very small voltage and current for

00:44:53

it to open and in this case even

00:44:56

pass through a person, the potential

00:44:58

will be enough to open our

00:45:01

transistor, let's make sure of this in

00:45:03

practice, we will find a transistor in all components,

00:45:06

do not confuse it with

00:45:08

temperature sensors or other elements

00:45:11

that also have three legs, look,

00:45:14

there are npn and pnp, well, let's take

00:45:16

the mpr, we'll work with it

00:45:19

accordingly, we'll try collect the

00:45:21

same shooting with a touch sensor, I'm a virus, a

00:45:26

new LED and a resistor, here's a resistor,

00:45:30

here's an LED and

00:45:33

take another resistor that will

00:45:36

represent such a person with a

00:45:39

lot of resistance, and so the LED is

00:45:43

Stalin, but somewhere closer let's turn the

00:45:46

transistor around like this,

00:45:48

accordingly, and

00:45:50

put it in a more comfortable position and Let's set the

00:45:52

resistance to 450.

00:45:55

You need to pay attention to which side,

00:45:58

which terminals are on the transistor, collector,

00:46:02

base, emitter, you can see in our diagram,

00:46:06

connected to the emitter, minus,

00:46:09

connected to the collector, connected directly to the consumer,

00:46:11

well, let's connect it like this 1 2, well,

00:46:15

let it be green and so

00:46:17

I have some transistor I connect to the collector,

00:46:20

commenting, I connect the power minus

00:46:23

like this, black from the base we will

00:46:26

just have the contact of our touch sensor coming out,

00:46:30

and we

00:46:31

need to somehow supply voltage to this base; the

00:46:34

voltage will be

00:46:36

supplied to us through a resistor, so we will

00:46:39

do it like this with you;

00:46:42

everything plus passes through the resistor

00:46:47

goes to our base, the transistor

00:46:50

opens and closes the chain, the

00:46:53

minus goes through the emitter inside the

00:46:57

transistor through the collector and goes to the

00:46:59

cathode of the LED,

00:47:01

then to the resistor, and of course here you

00:47:04

need to supply a plus supply of 9 volts.

00:47:08

Well, to make it more clear, let’s

00:47:10

connect another button like this, which

00:47:13

will actually be this is our

00:47:16

voltage supply, so

00:47:19

look again now, no voltage can

00:47:21

be applied, we start pressing the button and

00:47:24

we see that everything works fine, let's

00:47:27

try to change our resistance,

00:47:29

for example, to 3 kilo-ohms, let's assume that our

00:47:32

human skin is

00:47:35

so rough and dry, and even if we measured

00:47:39

the resistance, we got three kilos we'll

00:47:41

see if it works when

00:47:43

I press the button and we see how the LED lights

00:47:48

up quietly from this resistance. Usually human

00:47:50

resistance is taken into account that

00:47:52

we have one kiloohm of skin resistance, so

00:47:55

our touch sensor will work not

00:47:57

only if you take it with your two

00:48:00

hands, but also if next to you

00:48:03

will hold hands and there 6 8 10 people

00:48:06

your resistance will be formed anyway,

00:48:08

this current will be enough for the

00:48:10

LED to light up, you can experiment at home yourself, the

00:48:15

guys and I

00:48:16

tried in lessons, eight people in our

00:48:19

group joined hands and

00:48:22

accordingly the LED lit up at

00:48:24

full brightness then there is a transistor

00:48:26

opened, that's all I wanted to

00:48:28

tell you about bipolar transistors, but

00:48:30

you must remember that there are not only

00:48:33

bipolar and field-effect transistors, for example,

00:48:35

and so on, we will talk about them

00:48:37

no longer as part of the course on the basics of

00:48:39

electronics, for now this will be

00:48:41

enough for you to assemble yours first

00:48:44

interesting shootings and projects

00:48:47

[music]

00:48:51

well, we’ve already studied

00:48:54

quite a large number of

00:48:55

electronic components, let’s

00:48:57

try to assemble a project from them

00:49:00

called a light alarm clock, what will it be

00:49:03

like

00:49:04

if it’s dawn or, in

00:49:07

principle, it will be light when it rings and beeps?

00:49:11

if it’s dark around it, it means it will

00:49:14

simply be silent, that is, without resorting to

00:49:17

any programming or a

00:49:18

controller, you can simply

00:49:21

make such an interesting

00:49:23

project using electronic components. Of course, we will need a

00:49:25

component that can produce sound, and

00:49:28

as such a component we will take a

00:49:31

piezo emitter, look, this is new for

00:49:33

us too the component looks like this, it

00:49:36

has this

00:49:39

symbol where the pros and

00:49:43

cons are noted, how to connect it correctly, that is, it is a

00:49:45

polar element and in fact

00:49:48

there are two types of piezo emitter:

00:49:52

active or passive, what is the difference in a

00:49:55

passive piezo emitter,

00:49:56

such a piezo element is installed,

00:49:59

which is output just a plus and a minus, that

00:50:02

is, in fact, here inside this

00:50:05

recipient we have only

00:50:07

such a plate installed, you saw two contacts

00:50:09

to connect to it, what is a

00:50:12

piezoelement, essentially this plate to

00:50:16

which if you apply voltage,

00:50:18

it begins to deform, so to speak,

00:50:21

with some or from the sides, that is, it

00:50:24

was straight if you look at it like this,

00:50:26

if you apply voltage,

00:50:28

it begins to bend like this, so

00:50:31

if we apply voltage then

00:50:34

remove it, then the plate will accordingly

00:50:36

become either flat or curved,

00:50:38

flat or curved, and thus if we

00:50:41

do this very quickly, you and I

00:50:43

will get air vibrations, and

00:50:46

air vibrations from physics, maybe you remember

00:50:48

that this is sound in our situation,

00:50:51

we don’t yet know how to make it so that the

00:50:53

passive piezo emitter receives something plus that,

00:50:57

not something plus that there is nothing, and

00:50:59

therefore we will use an active

00:51:02

play detector with you, what does this mean? an

00:51:04

active play detector has a

00:51:07

special circuit installed inside that

00:51:10

actually does what makes

00:51:13

such a play record

00:51:16

vibrate with a certain frequency,

00:51:18

that is, it essentially

00:51:20

produces sound, for example, with a frequency of 400 50

00:51:24

times per second or 450 hertz on this

00:51:28

plate makes it do these

00:51:30

oscillations and we hear it directly in the form of

00:51:33

the sound of such squeaking, it’s

00:51:35

even a little disgusting and you

00:51:40

can distinguish an active from a passive piezo emitter, well, firstly, if this is a

00:51:44

new component, again look at the length of the legs

00:51:46

active, the short leg

00:51:49

minus the long one is a plus; for the passive, both

00:51:52

legs are the same length, they do not differ,

00:51:55

and also usually such an element, if it is

00:51:59

new, has a sticker indicating which

00:52:01

side it should be connected to the plus,

00:52:04

since I say again, there is

00:52:06

a circuit installed inside that generates

00:52:08

special impulses so that the plate

00:52:10

bends Also, on the body of the plays itself,

00:52:14

the detectors are a little invisible here, but

00:52:16

there is

00:52:17

such a small engraving with a

00:52:20

plus icon, you can also navigate by it; the

00:52:23

passive one has nothing like that and,

00:52:25

accordingly, you must understand that you

00:52:27

will have to send signals to it separately somehow

00:52:29

and so that you and I can feel

00:52:31

better you can see how our circuit works, we will

00:52:35

temporarily replace the piezo emitter with a regular

00:52:38

incandescent lamp in a tinker so that

00:52:41

we can see how our light

00:52:43

alarm clock works so that he does not constantly

00:52:45

write about it there and cannot make out how

00:52:47

much voltage is

00:52:49

coming to it, and so on we So far, replacing it with

00:52:52

just a regular lamp, and plus, in

00:52:55

kicker cody there is no active

00:52:57

piezo emitter, there is only a passive one, and

00:52:59

we have not yet learned how to generate

00:53:01

signals for it. A little later in the next

00:53:04

lessons we will talk about how to

00:53:06

actually do this. The next question

00:53:08

we should ask ourselves is this

00:53:10

of course, what component to take to

00:53:13

find out whether it is day or night and

00:53:16

you and I know that there is a

00:53:19

photoresistor component whose resistance

00:53:21

depends on the level of illumination, remember

00:53:24

that the photoresistor it has, the less light the

00:53:27

more resistance the more

00:53:30

light the less resistance you

00:53:32

must remember from the previous lesson and

00:53:34

let's try to invent a light alarm clock from scratch,

00:53:36

that is, I won't show you the

00:53:38

final circuit and how it should

00:53:41

look, we'll try step by

00:53:43

step to invent it ourselves, so to

00:53:46

speak, so let's just try

00:53:49

now to

00:53:50

connect our photoresistor and

00:53:53

incandescent lamps Let's see how they generally

00:53:54

behave and whether this is suitable

00:53:57

as an alarm light or not, let's go to

00:54:00

everyone's pick from so let's

00:54:02

find the necessary components in temper cadi, here it is, a

00:54:04

photoresistor, an

00:54:05

incandescent lamp and a battery, we need

00:54:10

9 volts, that's all for now, I'll try it

00:54:13

with you actually connect this to

00:54:15

some kind of circuit, but here for now

00:54:18

we only have one choice -

00:54:19

connect everything in series like this, let's

00:54:22

try to run it and see what will

00:54:25

happen, and so now on the photoresistor

00:54:27

and it's dark, I start to increase the lighting

00:54:31

and gradually, along with the increase in

00:54:33

our illumination level Logically,

00:54:37

the lamp starts to light up and will be shown until

00:54:39

the resistance drops completely to

00:54:42

almost 0. Of course, for indicators

00:54:45

of how light it is on the street, such a

00:54:47

scheme would be suitable, but our alarm clock

00:54:50

should work as it should

00:54:52

work sharply; they are like this, gradually

00:54:57

increasing, we turn on the star, this is a slightly

00:54:59

different type of alarm clock with dawn,

00:55:01

which begins to buzz us until we

00:55:04

need it, you and I can note that

00:55:06

now the more light in the room, the

00:55:09

louder our alarm clock sounds, and

00:55:12

this is not very logical, we need sharp

00:55:15

triggering so that as soon as the light

00:55:18

has overcome a certain level, ours

00:55:21

will turn on let's think about what we

00:55:23

can take to make something

00:55:26

suddenly turn on or open,

00:55:29

of course, this is the npn transistor we studied

00:55:32

with its own base

00:55:35

and emitter to the collectors, I remind you that the npn

00:55:39

transistor opens for us when

00:55:42

sufficient current and voltage are supplied

00:55:44

to base, that is, a potential difference will be created between the base and the

00:55:47

emitter, then

00:55:50

our transistor will open, let's

00:55:52

try to add it to our circuit in

00:55:55

that cerca de, we will find an

00:55:57

npn type transistor, take it and here you will need to

00:56:01

slightly swap the wires, so

00:56:04

to speak, accordingly, let's remove them all

00:56:06

for now,

00:56:08

connect the transistor I unfold it so

00:56:11

that it was more convenient, we remember that according to the diagram

00:56:14

we connect the collector to the load on

00:56:17

the camera, we just connected the minus with you,

00:56:19

but this is what we will do now, I

00:56:22

apply the minus to the emitter

00:56:27

plus, accordingly, I begin to apply

00:56:32

to the lamps

00:56:34

[music]

00:56:35

here the collector is minus,

00:56:40

that is, essentially our transistor, being a

00:56:43

resistance, so to speak, will begin to

00:56:46

pass minus whoever it hits the

00:56:48

lamp and the light bulb will turn on. How to

00:56:50

turn it on, you need to apply a positive potential to the base, you

00:56:55

need to do this through a photoresistor, well,

00:56:59

let's do it and make a terminal, I take

00:57:01

the photoresistor, connect it to the base in

00:57:04

red, I will do it since this is a plus, well, you

00:57:07

need to submit a plus here, which means you

00:57:08

can take it either here or over there, well,

00:57:11

let me take it here, well, let’s

00:57:13

do something like this, which is not very convenient

00:57:15

wiring, everything in fact, our

00:57:18

improved circuit is ready,

00:57:20

let’s try to simulate and and

00:57:24

so look now the light bulb Note that it’s

00:57:27

already glowing before, it wasn’t glowing before and

00:57:30

let’s try to add a brightness level, that

00:57:33

is, look what’s happening, I

00:57:35

raised the level a little and my

00:57:37

lamp already flashed brightly, but I remember that instead of a

00:57:40

lamp we have a piezo emitter, which means

00:57:43

that now in this state it would

00:57:44

rather not beep at all since this is a

00:57:47

small voltage for it to turn on,

00:57:49

it needs about five and three volts like this,

00:57:52

but as soon as the brightness level

00:57:55

rises a little bit, my light bulb

00:57:58

flashes brightly, this means your alarm clock

00:58:00

will beep very loudly; it’s already

00:58:02

what we wanted, but so far it’s

00:58:05

inconvenient It’s convenient for me that it’s literally a

00:58:07

small dawn and my alarm clock has already turned on. It

00:58:09

would be more convenient to somehow adjust this

00:58:12

matter so that you can set a

00:58:16

certain level of illumination at

00:58:18

which the alarm clock will turn on. Let’s

00:58:21

stop the simulation and add a

00:58:23

potentiometer to our circuit. I remind you that we have

00:58:27

it too we studied its

00:58:28

resistance depends on two turns and

00:58:32

the knob, so this, in my opinion, is the most

00:58:34

suitable component so that you can

00:58:36

precisely adjust the level of illumination

00:58:39

at which the alarm clock should go off,

00:58:41

let's try to connect it to our

00:58:44

circuit and here the question arises: how will we

00:58:48

connect the photoresistor and

00:58:50

potentiometer using a voltage divider,

00:58:54

more precisely according to the voltage divider circuit,

00:58:56

let's see now in the

00:58:59

voltage dividers, instead of 1 resistor

00:59:01

there will be a photoresistor, instead of 2

00:59:04

resistors there will be a potentiometer, that

00:59:07

is, it will look something like

00:59:09

this and the middle point that they

00:59:11

will divide will be sent to base of

00:59:14

the transistor and thanks to this circuit,

00:59:17

we will get precise adjustment of the

00:59:19

voltage level that we want to

00:59:21

receive. I hope you remember the circuit I

00:59:23

showed how two resistors

00:59:25

depend on each other. Here the same thing is true: if we

00:59:28

measure the voltage, for example, on a

00:59:30

potentiometer, then it will be low at first,

00:59:34

then, on the contrary, high and from this we

00:59:36

will get that the base of the transistor at a

00:59:38

certain moment

00:59:40

will create the required potential difference

00:59:42

between the base and the emitter and the transistor

00:59:44

will open what we needed,

00:59:47

let's convert our circuit again,

00:59:49

now to a photoresistor, I add

00:59:53

a potentiometer, we must take either this and

00:59:56

this point

00:59:58

or the top and middle, that is, not at

01:00:01

the edges, not terminal 1 and terminal 2, this is where

01:00:04

we change the resistance on the sliding VKontakte contacts, that’s what

01:00:06

you

01:00:08

and I will connect, so I take the sliding

01:00:11

contact, send it to see where I create the

01:00:15

middle point, so to speak, look, it’s fed

01:00:18

plus passes on the photoresistor at

01:00:22

this point the voltage begins to divide,

01:00:24

gets to the base of the transistor and then

01:00:27

goes to the potentiometer here,

01:00:30

respectively, we connect it all to the

01:00:32

negative

01:00:33

here and so the next step is to

01:00:35

set the resistance of our potentiometer

01:00:38

since 250 kilo-ohms is too much,

01:00:42

you remember that that photoresistor has 180

01:00:45

this one has 250 and they will fight with each other

01:00:48

and as a result, a

01:00:50

not too big difference between them

01:00:53

will arise in voltage and our transistor

01:00:55

will essentially constantly

01:00:57

open almost as soon as we change

01:01:00

the resistance, this is not very good,

01:01:02

so we immediately lower it so that

01:01:05

the potentiometer loses, so to speak in

01:01:07

voltage and, in fact, we

01:01:10

measure our voltage from it on the base, so

01:01:12

I’ll set it a little somewhere, 1

01:01:14

kilowatt, for example, let’s try now to

01:01:17

start modeling,

01:01:19

you turn the knob like this on

01:01:23

the photoresistor and start raising the sun, we

01:01:26

see that our transistor is not turning on yet

01:01:28

and at the maximum level it

01:01:30

still doesn’t turn on, which means you need to

01:01:32

add a little

01:01:34

potentiometer to the resistance,

01:01:37

look, at this resistance,

01:01:40

my alarm clock religiously lights up, I begin

01:01:44

to lower the brightness a little and we see

01:01:47

that at about this level

01:01:50

my alarm clock worked well,

01:01:52

let’s do more let's raise it a little like this,

01:01:56

then it will go off a little

01:01:59

earlier, you see, about halfway through, and

01:02:01

this way you and I will get that

01:02:04

not immediately as soon as

01:02:06

the dawn has begun a little and our alarm clock

01:02:08

turns on a little later, about

01:02:11

here, with such average illumination, of course,

01:02:15

at In practice, this can be adjusted more

01:02:18

accurately, it will work fine for you,

01:02:21

but we see that in this

01:02:23

range now, despite the full

01:02:25

brightness,

01:02:26

the light bulb and the brightness does not change in any way,

01:02:29

which means the sound will not change, this

01:02:32

threshold is somewhere around here, so we

01:02:34

you and received the alarm clock light circuit,

01:02:37

this is how it looks in principle,

01:02:39

we see a voltage divider

01:02:41

which, accordingly,

01:02:43

unexpectedly was found here, and if we had

01:02:46

looked earlier, we would have seen just

01:02:48

two resistors here and that’s all, but now we

01:02:50

know where the two resistors are connected

01:02:52

plus - minus there is a middle pin, which means it is a

01:02:55

divider; by the way, the recording can be

01:02:57

used not only as an

01:02:59

alarm clock, but also as a mini

01:03:02

light alarm, for example, you can

01:03:04

take this circuit and put yourself in a

01:03:06

closet somewhere where it’s dark, and if someone

01:03:10

breaks into your closet, you’ll know about

01:03:12

it you will find out because the light will hit the

01:03:15

photoresistor, this is an interesting

01:03:17

use you can make for it, I hope you found it

01:03:20

interesting and now you can safely

01:03:22

start your homework

01:03:24

[music]

01:03:27

and as a homework

01:03:29

try to connect a multimeter to

01:03:33

our circuit and try to measure

01:03:36

all sorts of voltages on it the

01:03:38

voltage between the collector and the emitter

01:03:40

now what is the voltage between the

01:03:43

base and the emitter, look how it

01:03:45

increases or decreases depending on the

01:03:48

settings of the photoresistor and potentiometer,

01:03:51

we have figured out how the multimeter

01:03:53

works here, it is absolutely no

01:03:56

different, there are only three buttons for you to

01:03:58

select the limits measurements, so all that

01:04:01

remains is to simply connect the positive

01:04:03

output somewhere and, accordingly, the

01:04:05

negative one in the settings, you can

01:04:07

select the voltage, current or

01:04:09

resistance, try

01:04:11

experimenting

01:04:16

[music]

01:04:21

[music]

01:04:29

[music]

Description:

Сегодня познакомимся с мультиметром, изучим работу переменных резисторов и транзистора, а так же соберем схемы "датчика касания" и "светобудильника". Я постарался сделать, пожалуй, самый простой и понятный курс по электронике который ты встретишь в рунете. Материал этого курса не загрузит тебя сложными терминами или формулами - в "живом" формате его прошли уже свыше 500 учеников моей школы робототехники, поэтому я уверен, что после его просмотра для любого новичка электроника станет легкой и понятной. Кстати, работать мы будем в виртуальной среде моделирования схем, так что не беда, если у тебя пока нет нужных компонентов под рукой. ------------------------------------------------------------------------------------ Группа ВК: https://vk.com/lrazum Страница автора в Instagram: https://www.facebook.com/unsupportedbrowser ------------------------------------------------------------------------------------ 0:00 - Начало 0:18 - Проводим измерения - мультиметр 12:31 - Компоненты: Потенциометр (переменный резистор) 21:03 - Компоненты: Фоторезистор 24:30 - Резистивный делитель напряжения 33:42 - Компоненты: Биполярный PNP и NPN-транзистор 43:59 - Мини-проект “Датчик прикосновения” 48:48 - Итоговый мини-проект “Светобудильник” 1:03:26 - Домашнее задание

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