555 Chip Explained - LED Blinker, Buzzer, Siren...

Summary

This video tutorial offers an in-depth introduction to the 555 oscillator chip, a staple in electronics for over 50 years. It explains the function of all eight pins and demonstrates how to create simple circuits like LED blinkers and beepers with varying frequencies. The video also covers the impact of different resistor and capacitor values on oscillation speed, introduces the concept of duty cycles, and explores the use of the chip's lesser-known pin five for unique applications. Viewers are guided through building oscillators with fixed and variable frequencies, offering a comprehensive foundation for beginners in circuit design.

Takeaways

• 😀 The 555 oscillator chip is an essential component for beginners in electronics, commonly used for over 50 years.
• 🔌 The 555 chip has 8 pins with pins 1 and 8 serving as the supply voltage connections, pin 1 being ground and pin 8 the positive supply.
• 🔄 Pins 3 and 7 are the two main outputs of the 555 chip, functioning as switches controlled by internal transistors.
• 🔩 The 555 chip operates with two main inputs, pins 2 and 6, which control the flipping of the outputs based on voltage levels.
• 🔄 An additional reset input can override the outputs, but is often left unconnected or connected to the positive supply to disable its effect.
• 🔄 The 555 chip can be easily turned into an oscillator due to its inverting effect on the inputs and outputs.
• 💡 By connecting LEDs to the outputs, one LED will light up when the output is low and the other when it's high, creating an alternating blink.
• ⚡ The frequency of the oscillator can be adjusted by changing the values of the resistor and capacitor in the circuit.
• 🔊 A beeper can be created using a small speaker with the 555 chip, requiring higher frequencies achieved by using lower capacitance values.
• 🔄 Pin 5 of the 555 chip can be used to manipulate threshold values, influencing the frequency and duty cycle of the output.
• 🔄 The duty cycle of the oscillator can be altered by using a potentiometer or by changing the resistor values, allowing for unequal blinking of LEDs.

Q & A

What is the 555 oscillator chip?

The 555 oscillator chip is a versatile integrated circuit used in various electronic applications, including the creation of oscillators, timers, and pulse generators. It has been in production for over 50 years and is often one of the first chips that beginners in electronics learn about.

How many pins does the 555 oscillator chip have?

The 555 oscillator chip has eight pins, each serving a specific function, such as supply voltage connections, outputs, and inputs.

What are the functions of pin 1 and pin 8 on the 555 chip?

Pin 1 is the ground pin, connected to 0 volts, and pin 8 is the positive supply voltage pin, typically receiving a voltage between plus 5 to +15 volts from a DC power supply or battery.

What are the two main outputs of the 555 chip?

The two main outputs of the 555 chip are pin 3 and pin 7. These outputs can be in two states, high or low, and are controlled by internal transistors acting as switches.

How do the inputs of the 555 chip affect the outputs?

The inputs of the 555 chip, specifically pins 2 and 6, control the state of the outputs. When the voltage at pin 2 goes below 1/3 of the supply voltage, the outputs flip up. When the voltage at pin 6 goes above 2/3 of the supply voltage, the outputs flip back down.

What is the purpose of the reset pin on the 555 chip?

The reset pin, when connected to 0 volts, overrides the other inputs and forces the outputs to flip down. It is often left unconnected or connected to the positive supply rail to disable its effect.

How can the frequency of a 555 oscillator circuit be adjusted?

The frequency of a 555 oscillator circuit can be adjusted by changing the values of the resistor and capacitor used in the feedback loop. Higher resistance or capacitance results in a slower frequency, while lower values result in a faster frequency.

What is the function of pin 5 on the 555 chip?

Pin 5 on the 555 chip is connected to the internal resistive divider and can be used to manipulate the threshold values for pins 6 and 2, which affects the frequency and duty cycle of the output. It can also be used as a filter to prevent noise on the supply rail from affecting the threshold values.

How can the 555 chip be used to create a variable frequency oscillator?

A variable frequency oscillator can be created by adding a potentiometer in series with the resistor in the feedback loop of the 555 circuit. Adjusting the potentiometer changes the resistance, which in turn changes the frequency of the oscillator.

What is the purpose of connecting a capacitor to the supply rails in a 555 circuit?

Connecting a capacitor between the positive and negative supply rails, often referred to as decoupling or bypass capacitor, helps stabilize the circuit by filtering out any noise or fluctuations in the power supply. It is typically a polarized electrolytic capacitor with a value ranging from 100 to 1000 microfarads.

How can the 555 chip be used to create a beeper circuit?

A beeper circuit can be created by connecting a small speaker to the output of a 555 oscillator circuit. The frequency of the oscillator needs to be high enough for the speaker to produce an audible sound. Capacitors with lower values are used to achieve higher frequencies.

What is the effect of connecting a diode in the oscillator resistor of a 555 circuit?

Connecting a diode in the oscillator resistor allows the LEDs to blink unequally, changing the duty cycle of the oscillator. Without the diode, the duty cycle is always 50% or higher, but with the diode, any duty cycle can be achieved depending on the ratio of the resistors.

Outlines

00:00

🔌 Introduction to the 555 Oscillator Chip

This paragraph introduces the 555 oscillator chip, a common component in electronics, particularly for beginners. It explains the chip's eight pins, including the supply voltage pins (1 and 8), and the two output pins (3 and 7) that function as switches controlled by internal transistors. The paragraph also covers the two main input pins (2 and 6) that determine when the outputs flip based on voltage levels, as well as the less commonly used reset pin. The 555 chip's oscillator function is highlighted, demonstrating how it can create an oscillating circuit with the right components, such as resistors and capacitors, to control the frequency.

05:00

💡 Building an LED Blinker Circuit with the 555 Chip

The second paragraph delves into constructing an LED blinker circuit using the 555 chip. It describes how to connect LEDs to the chip's outputs, with one LED lighting up when the output is low and the other when it's high, creating an alternating blinking effect. The importance of stabilizing the circuit with a capacitor across the supply rails is emphasized, along with the impact of varying resistor and capacitor values on the blink rate. The paragraph also explains the role of the internal resistive divider and pin 5 in setting threshold voltages for the inputs, and how manipulating these can influence the circuit's frequency and duty cycle.

10:03

🔊 Creating a Variable Frequency Oscillator and Beeper

This paragraph discusses creating a variable frequency oscillator using a potentiometer to adjust the blink rate of an LED blinker circuit. It then transitions to building a beeper circuit with a small speaker, explaining the need for higher frequencies and the use of different capacitor values to achieve this. The speaker is connected via a capacitor to receive the AC signal, not DC, and the frequency can be adjusted to produce different sounds, from clicks to buzzes. The paragraph also touches on experimenting with pin 5, using it to control a blinking LED and create a siren effect.

15:05

🔄 Advanced Oscillator Techniques and Applications

The final paragraph covers advanced techniques for the 555 oscillator, such as using pin 7 for feedback to create a more stable oscillator, adjusting the duty cycle with resistor values, and using a diode to create unequal on-off times for the LEDs. It also mentions the possibility of using the 555 chip in non-oscillating circuits, like a flip-flop or monostable timer, and hints at further exploration of these topics in future videos. The paragraph concludes with an invitation for viewers to support the channel and a mention of a bonus circuit, encouraging continued interest and engagement.

Keywords

💡555 Oscillator Chip

The 555 oscillator chip is a versatile integrated circuit used for generating accurate and stable time delays or oscillation. In the video, it is the central component around which various circuits are built, such as LED blinkers and beepers. The script explains its pin functions and how it can be configured to create different types of oscillators, emphasizing its importance in the theme of building electronic circuits.

💡LED Blinker

An LED blinker is a simple electronic circuit that causes an LED to turn on and off at regular intervals. The video script describes how to create an LED blinker using the 555 oscillator chip, illustrating the practical application of the chip in a beginner-friendly project. The blinker serves as an example of how the 555 chip can be used to generate time-based signals.

💡Beeper

A beeper in the context of the video refers to a circuit that produces sound pulses using the 555 oscillator chip. The script mentions creating a beeper with two frequencies, demonstrating the chip's capability to generate audible signals for various applications. The beeper exemplifies the audio output potential of the 555 chip.

💡Variable Frequency

Variable frequency refers to the ability to change the rate of oscillation in a circuit. The video script explains how to modify the frequency of the 555 oscillator circuit by altering the values of the resistor and capacitor, which is key for creating circuits with adjustable speed or pitch, such as the variable frequency blinker and beeper.

💡Pin Functions

Pin functions describe the purpose of each pin on the 555 oscillator chip. The script provides a detailed explanation of the eight pins, including supply voltage pins, output pins, and input pins, which are crucial for understanding how the chip operates within the circuits discussed in the video.

💡Logic Chip

A logic chip, as mentioned in the script, is a type of integrated circuit that performs logical operations and can have outputs in only two states, typically represented as 0 (low) and 1 (high). The 555 chip is described as a logic chip, emphasizing its digital nature and how its outputs are controlled by internal transistors acting as switches.

💡Oscillator

An oscillator is a circuit that generates a repetitive signal, often a square wave. The video script explains how the 555 chip can be configured as an oscillator by providing feedback from the output to the input through a resistor and capacitor, which is fundamental to the operation of the circuits presented.

💡Duty Cycle

Duty cycle refers to the ratio of the time a signal is active (high) compared to the total period of the signal. The script discusses adjusting the duty cycle of the 555 oscillator by modifying resistor values or using a diode, which affects how long the output is high versus low, impacting the behavior of the LED blinker.

💡Resistor

A resistor is a passive component that opposes the flow of electric current in a circuit. The video script frequently mentions resistors, explaining how their values affect the frequency and duty cycle of the 555 oscillator circuits, such as in the LED blinker and beeper examples.

💡Capacitor

A capacitor is a component that stores electrical energy and can smooth, filter, or delay voltage changes in a circuit. The script describes using capacitors in conjunction with resistors to determine the frequency of the 555 oscillator circuits, as well as to create stable operating conditions.

💡Potentiometer

A potentiometer is a type of resistor with a sliding contact that allows for continuous adjustment of resistance. The video script describes adding a potentiometer to the oscillator circuit to create a variable frequency, demonstrating a practical way to adjust the speed of the circuit manually.

💡Internal Resistive Divider

An internal resistive divider in the context of the 555 chip is a network of resistors within the chip that sets the voltage threshold levels for the input pins. The script explains how this divider creates the 1/3 and 2/3 supply voltage levels that determine when the chip's outputs flip, which is essential for the operation of the oscillator circuits.

💡Output Pin

Output pins on the 555 chip, such as pin 3 and pin 7, are used to provide the signal from the chip to external components like LEDs or speakers. The script discusses how these pins can be configured to drive different types of loads and how their behavior can be influenced by the circuit design.

Highlights

Introduction to the 555 oscillator chip, a common component for beginners in electronics.

Explanation of the 8 pins of the 555 chip, including supply voltage pins 1 and 8.

Description of the two outputs, pin 3 and pin 7, and their binary switching behavior.

Input pins 2 and 6 control the flip of the outputs based on voltage levels.

The reset pin's function and its priority over the other inputs.

Building a simple oscillator using the 555 chip with an inverting effect on the pins.

Use of a resistor and capacitor to control the frequency of the oscillator.

Connecting LEDs to the oscillator to visually indicate the blink rate.

The role of pin 5 in adjusting threshold values and its common applications.

Demonstration of changing the blink rate by altering resistor and capacitor values.

Construction of a variable frequency oscillator using a potentiometer.

Creating a beeper circuit with the 555 chip and adjusting frequency for audible sound.

Experimentation with pin 5 to control the blinking of an LED integrated into the circuit.

Use of pin 7 for oscillator feedback and the need for a pullup resistor.

Adjusting the duty cycle of the oscillator by manipulating resistor values.

Implications of using extremely low or high resistances in the oscillator circuit.

Introduction of non-oscillating 555 chip circuits like the flip-flop and monostable circuits.

Invitation to support the channel for further detailed exploration of 555 chip applications.

Transcripts

so today a video for beginners

explaining a 555 oscillator chip and

some simple circuits with it like an LED

blinker and a beeper or even a beeper

with two frequencies and a variable

frequency blinker I will show the

schematics of these circuits but first

let's explain what all the pins of the

555 oscillator chip do a 555 oscillator

chip has eight pins and in reality it

looks like this and there are different

versions from many different makers and

they're making this one for over 50

years now and it's a very common chip

and for beginners in electronics very

often the first chip they learn about

first let's take a look at the pin one

and eight these are the supply voltage

pins pin one is the ground connected to

0 volts and pin 8 is the positive Supply

voltage and it's typically from plus 5

to + 15 volts from a DC power supply or

from a battery and then it has two

outputs pin three and pin 7 and this is

a logic chip not an analog chip so the

outputs can be just in two states

nothing in between and the outputs are

switched by internal transistors in it

which you can imagine for Simplicity as

switches the pin three can be either

switched to the Z volt rail the ground

or to the positive Supply

Rail and then there is another output

pin 7 called mysteriously discharge

acting sort of similar as this one but

it only switches to the Zer volt rail or

to nothing and they of course

synchronized they always flip at the

same time but this one connected to the

pin 7 only switches to the ground not to

the positive of course in reality this

output is an npn transistor with an open

collector but let's not make it too

complicated so these two pins are the

outputs they work like switches but what

makes these switches flip they flip

based on what happens at the inputs the

555 chip has two main inputs the pins 2

and six plus an additional input reset

the output skan flip based on what

happens at the inputs first let's take a

look at this input pin two when the

voltage at this input goes below 1/3 of

the supply voltage the switches flip up

this output gets the supply voltage on

it and this output is disconnected now

they basically flipped into the upper

position here so now we flip the

switches up and how do we flip them back

down when the voltage at this input pin

six goes above 2/3 of the supply voltage

they flip back down so they're again in

this

position both outputs connected to the Z

volt rail or ground so one input flips

the outputs up when the voltage goes low

enough and one flips them down when the

voltage goes high enough and in most

oscillator circuits these two inputs pin

six and and pin two are connected with

each other so they basically work as

just one input which can flip the

outputs both up and down and there is

one more input which is not used very

often is the reset pin and this flips

the outputs down when it's connected to

0 volts but in most cases it's unused

you can leave the pin unconnected but

it's better to actually connect it to

the positive Supply rail to basically

disable it so it has no effect and of

course the inputs have some priority is

the reset input has the highest priority

so if this is connected to 0 volts it

flips the outputs down and it doesn't

care about the input six and two and

then input two has a lower priority and

the input six the lowest one if you for

example pull pin two under 1/3 of the

supply voltage and pin six

simultaneously above 2/3 of the supply

voltage the pin two has a priority end

so the outputs flip up but this never

happens when these two are connected

with each other there of course but now

let's build a very simple oscillator out

of it the pins have an inverting effect

so it's easy to turn it into an

oscillator when this pair of penis is

pulled higher the output goes low and

when it's pulled lower the output goes

high it's inverting so it can form an

oscillator when basically the output

goes back into the inputs but of course

it shouldn't be connected directly it

has to go via a

resistor now with this feedback it's

basically an oscillator but it would

oate extremely fast so we have to make

it slower by adding a capacitor the

inputs and the here the capacitance the

slower it is the lower the frequency of

the oscillator and also the higher the

resistance of this resistor the slower

the oscillator is or its output

frequency is lower now the circuit

oscillates but we can't see it because

there is no indication so let's connect

some LEDs to it he connected a pair of

LEDs this one lights up when the outputs

are low and the current goes from the

positive Supply rail through this

led into this output and into the Z volt

Rail and when this output is high the

current goes from the supply rail

through the

output through this LED and to the Z

volt rail so it's always one LED on and

the other one off I gave the component

some values these resistors are 560 ohms

it's not critical it can be for example

one kiloohm as well this resistor is 470

KMS and this capacitor is 1 microfarad

ceramic capacitor and the circuit looks

like this the LEDs are alternately

blinking but of course it's a good

practice as you can see to connect a

capacitor to the supply rails between

the positive and the negative like this

for stability of the circuit typically

this capacitor is from 100 microfarads

to 1,000 microfarads and it's an

electrolytic capacitor which is

polarized and it's negative for a z volt

terminal it's marked using this stripe

with a minus symbol which goes to the

first pin of this chip and how this

circuit works when the output is high it

basically charges via this resistor this

capacitor and it's charged until it

reaches 2/3 of the supply voltage and

then it flips and this output is low and

Via this resistor it discharges this cap

until it reaches 1/3 of the supply

voltage and then the output flips back

too high and it keeps repeating so for

example our supply voltage is 6 Vols of

battery let's say so the voltage at this

capacitor and the inputs looks like this

the capacitor charges to 2/3 of the

supply voltage and this charges to 1/3

and this keeps

repeating and the output pin three goes

like this 6 Vol 0 Vol 6 Vol 0 Vols while

the inputs are going between 2 volts and

4 Vols but of course if the supply

voltage was 12 volts it would be going

between 4 volts and 8 volts the

threshold levels always depend on the

supply voltage and these threshold

levels are created by an internal

resistive divider in the chip made of

three

resistors and there is one last

mysterious pin pin five and this one is

actually connected to this divider to

this spot on it and this spot is

actually used as the threshold value for

the pin six and the voltage on this spot

is used as the threshold voltage for the

pin Two And the pin five is very often

unused or it can be connected via a

capacitor to the Z volt rail as some

sort of a filter so the threshold values

are not influenced by the noise on the

supply Rail and this capacitor typically

is 100 nanofarad ceramic or this pin can

also be used to manipulate the threshold

values you can externally change the

voltage on this pin to change the

threshold values for the pin 6 and two

which in an oscillator influences the

frequency and Dy cycle at the output but

let's leave this spin for now and let's

go back to our blinker and let's try to

change the speed of it by changing the

values of these two components when I

replace the 470 kohm resistor using 1

Mega ohm resistor it's blinking slower

the higher the resistance the slower it

is the lower the

frequency and now I have an 82 km

resistor which is much lower resistance

so it should be much faster now and it's

blinking quite fast now let's replace

the 1 microfarad capacitor in the

oscillator using a 10 microfarad

capacitor a higher capacitance should

make it slower again and this one is

electrolytic it's polarized so this pin

has to go to the negative or 0 volt rail

and pin one of the chip let's replace

the capacitor and higher capacitance

makes it run slower the frequency is

lower now let's make an oscillator with

a variable frequency I added a

potentiometer in series with the

resistor in the oscillator here you can

see the potentiometer in the circuit and

by turning the potentiometer I can

change the

speed it's getting

faster and even

faster and the slower

again and here's the schematic of it and

now let's try to build a beeper I will

use this small speaker for it and the

frequency has to be much higher for this

I will replace the one microfarad

capacitor using a 100 nanofarad

capacitor a lower capacitance means a

higher frequency and it can be even

higher until it's so fast you can't even

see it

so I added a speaker to the circuit and

speakers are connected to the output via

a capacitor not directly so they only

get thec voltage not the DC and the

frequency is quite low so it's clicking

and when I increase

it it's

buzzing and to get the frequency even

higher let's replace this one 100

nanofarad capacitor using a 10 nanofarad

capacitor and now it's higher and I can

again adjust

it it works

[Music]

nicely now let's experiment with the pin

five who was a kid my favorite use for

it was to connect a blinking LED to it

it's an LED with a blinker built into it

and this blinking Le when connected to a

power supply just via resistor blinks on

its own thanks to its built-in blinking

circuitry now let's try to connect it to

the pin five it will go from the pin

five to the Z volt Rail and always in

LEDs the longer pin is theod or the

positive so the longer pin goes to the

pin five let's turn it on

and let's add the

El and we have a 2 siren and the is

blinking by the

[Music]

dimly he removed these eles and now we

have a 2o

siren

[Music]

and of course it's schematic and adding

a resistor going from the positive to

the pin five and the LED makes it blink

brighter and changes the behavior a

[Music]

bit and now let's go back from the

Beeper to the blinker to be able to

demonstrate how to use the pin 7 he was

previously connecting the oscillator

resistor from the pin 3 to the pin two

which makes the circuit a bit simpler it

saves one resistor but the feedback for

the oscillator can also go from the pin

seven to the pin 2 and six and this is

actually the recommended way of doing it

because if the resistor goes from the

pin three the oscillator might be

influenced by the load so it might be

better to use the output pin three just

for the load and the PIN 7 for the

oscillator but because the output 7 only

switches to the0 volt rail not to the

positive rail it requires an additional

pullup resistor so this is the main

oscillator resistor and this is the

pullup resistor and when you want to 50%

R the cycle which means the on time for

each LED is roughly equal you're using a

much lower resistance for the pullup

resistor and a much higher resistance

for the oscillator resistor in this

example I'm using just 10 KMS here and

400 20 KS here and because this one is

much higher than this one they blink

about equally but when this one has a

higher value in this example 470 khms

and this one at just 82 khms they are

blinking

unequally the green LED always stays on

much longer than the red one and with a

4.7 microfarad capacitor in the

oscillator which makes it

slower but again uny this resistance is

much lower than this one the LEDs will

blink

unequally and also regarding the

resistors in the oscillator it's not

recommended to use extremely low or

extremely high resistances the lowest

should be something like 4.7 KS and the

highest about 2.2 MGA very low

resistances loads the chip too much and

with very high resistances the leakage

currents show up and this recommendation

applies to both resistors here or the

resistor here in the previous examples

and now I went back to these values

which make an equally blinking

oscillator because this one is much

lower than this one and now let's

demonstrate the pin 4 let's disconnect

it from the positive and connect it to

the Z volt raail and when I do this it

will stop the oscillator now the output

stay low so the red LED is always on and

the current goes like this and of course

when these two resistors are used in the

oscillator the capacitor's charging via

the series combination of both resistors

but it's discharging just via this

resistor the capacitor's charging from

the positive rail through the two

resistors like this and it's

discharging theyjust this resistor and

into the pin seven and now the schematic

is a proper mass and one more example

circuit with an added diode on this

resistor in the oscillator now this

capacitor is charging just via this

resistor instead of the series

combination and it's discharging via

this

resistor and this allows the LEDs to

Blink unequally the other way now the

red one stays on longer in other words

the duty cycle of the oscillator can now

be below 50% instead of over

50% now the waveform is like this when

the green one stayed on longer the

waveform was like

this with the diode you can produce any

duty cycle basically depending just on

the ratio of these resistors but without

the diode the duty cycle is always 50%

or higher and the 555 oscillator can

basically produce square waves for many

different purposes from a fraction of a

Herz up to several 100 KZ and there are

also some circuits with a 555 chip that

are not oscillating for example a bable

circuit which can flip between two LEDs

or can be used for just one to turn

something on and off using push buttons

or a mono stable circuit basically a

timer but this video is getting too long

so if you're interested you can talk

about this in more detail in another

episode so that's it and if you like my

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