Sound Reactive LED Circuit Using LM358 Op-Amp and Mic

Summary

This video tutorial guides viewers on constructing a sound-reactive LED circuit. It explains the theory behind the circuit, detailing the function of each component including voltage dividers, an op-amp, feedback resistor, diode, and capacitor. The video also covers the step-by-step assembly process, emphasizing the importance of a condenser microphone to detect sound and trigger the LED. The goal is to create a circuit that lights up the LED in response to sound.

Takeaways

• 🎵 The video demonstrates how to create a sound-reactive LED circuit.
• 📚 It explains the theory behind the circuit and the purpose of each component.
• 🔊 The LED turns on in response to sound, as shown by the presenter speaking.
• 👍 The video encourages viewers to like and subscribe for more content.
• ⚡ Voltage dividers are used extensively in the circuit to regulate voltage levels.
• 🔗 A voltage divider is created by two resistors in series, explained with an example.
• 🔄 The script references another video on Ohm's law for further understanding of series and parallel circuits.
• 🔌 The first step in building the circuit involves connecting specific pins to the positive and negative rails.
• 🔄 A feedback resistor is used for negative feedback in the op-amp circuit.
• 💡 A diode is used to drop voltage when there is no sound, ensuring the LED turns off.
• ⏲️ A capacitor is included to filter out noise and prevent the op-amp from getting confused by extraneous signals.
• 🔋 The circuit is designed to work best with a 5-volt battery supply.
• 🎤 A condenser microphone is used to detect sound, changing its capacitance based on the sound it receives.
• 🔧 The final circuit allows sound signals to be processed and the LED to react accordingly.

Q & A

What is the main purpose of the video?

The main purpose of the video is to demonstrate how to make a sound-reactive LED and explain the theory behind its operation.

What is a voltage divider and how is it used in the circuit?

A voltage divider is a circuit with two resistors in series that creates a smaller voltage at its node by combining positive and negative voltages. It is used in the circuit to drop the voltage at specific points.

Why are there many voltage dividers in the circuit?

There are many voltage dividers in the circuit because they help to regulate and adjust the voltage levels where needed, which is essential for the proper functioning of the circuit.

What is the role of the operational amplifier (op-amp) in the circuit?

The operational amplifier (op-amp) takes two input voltages (inverting and non-inverting) and produces an output. It is used to amplify the difference between the two input voltages.

How is the voltage divider formed with resistors?

The voltage divider is formed by connecting a 10 kilo ohm resistor between pin 3 (non-inverting input) and the negative rail, and another 10 kilo ohm resistor from pin 3 to the positive rail.

What is the purpose of the feedback resistor in the circuit?

The feedback resistor, which is a high resistance resistor, provides negative feedback to the op-amp. It is connected between the inverting input and the output to stabilize the circuit.

Why is a diode used in the circuit?

A diode is used to drop the voltage when there is no sound, ensuring the LED turns off. The diode's characteristic of dropping voltage when current runs through it is utilized here.

What is the function of the capacitor in the circuit?

The capacitor, specifically a 0.47 microfarad capacitor, is used to filter out excess noise from the signal, preventing it from confusing the op-amp.

How is the LED connected in the circuit?

The LED's negative (cathode) is connected to the diode, and its positive (anode) is connected to the positive rail through a 270 ohm resistor.

What is a condenser microphone and how does it work?

A condenser microphone changes its capacitance based on the sound it receives. When it receives sound, the capacitance increases and this change is sensed by the circuit.

How does the sound signal travel through the circuit?

Sound signals enter through the condenser microphone, get regulated by the voltage divider, filtered by the capacitor, and then travel through the feedback resistor to the op-amp, where it is compared and ultimately controls the LED's state.

Outlines

00:00

💡 Building a Sound-Reactive LED Circuit

This paragraph introduces the project of creating a sound-reactive LED using an op-amp circuit. The host explains the importance of each component and how they work together. Voltage dividers are discussed, which are essential for regulating voltage levels in the circuit. The role of resistors, specifically 10 kilo ohm resistors, in creating these voltage dividers is highlighted. The operational amplifier (op-amp) is briefly reviewed, explaining its function of taking two input voltages and producing an output. The first step in the circuit assembly involves connecting pin 8 to the positive rail and pin 4 to the negative rail. A voltage divider is then formed with two 10 kilo ohm resistors at pin 3, which is the non-inverting input, to lower the voltage. The necessity for a feedback resistor, which is a high resistance resistor, is explained, and its placement between the inverting input and the output is detailed.

05:00

🔊 Completing the Sound-Reactive LED Circuit

The second paragraph continues the explanation of the sound-reactive LED circuit. It discusses the use of a diode to drop voltage when there is no sound, allowing the LED to turn off. The placement of the diode in relation to the op-amp output is described. A 0.47 microfarad capacitor is introduced to filter out excess noise and prevent the op-amp from getting confused by unwanted signals. The assembly of the circuit is detailed, including the connection of an LED to the diode and the positive rail through a 270 ohm resistor. The importance of using a 5-volt battery supply is mentioned, as a 9-volt battery may not provide the necessary sound sensitivity. The function of a condenser microphone, which changes its capacitance based on the sound it receives, is explained. The final steps of connecting the microphone to the circuit and the flow of sound signals through the circuit are outlined, concluding with the complete setup of the M358 op-amp circuit.

Keywords

💡Sound-Reactive LED

A sound-reactive LED is a type of LED light that changes its state (typically turns on or off) in response to sound. In the video, the LED turns on as the presenter talks, demonstrating the sound reactivity. This is the central project of the video, where the presenter explains how to create such a device.

💡Voltage Divider

A voltage divider is a passive linear circuit that produces an output voltage (Vout) proportional to the input voltage (Vin). In the script, voltage dividers are used to drop the voltage at certain points in the circuit, such as at the non-inverting input of the op-amp. They are essential for regulating the voltage levels that various components in the circuit receive.

💡Op-Amp

An operational amplifier (op-amp) is a DC-coupled high-gain electronic voltage amplifier with a differential input and, usually, a single-ended output. In the video, the LM358 op-amp is used to process the sound signal and control the LED's state. The op-amp takes two input voltages (inverting and non-inverting) and outputs a signal that is used to drive the LED.

💡Feedback Resistor

A feedback resistor is used in an op-amp circuit to provide negative feedback, which stabilizes the amplifier's operation. In the video, a one mega ohm resistor is used as a feedback resistor between the inverting input and the output of the op-amp. This helps to control the gain of the amplifier and ensures that the LED responds appropriately to the sound signal.

💡Diode

A diode is a two-terminal electronic component that allows current to pass predominantly in one direction. In the script, a diode is used to drop the voltage when there is no sound, which helps to turn off the LED. The diode's voltage drop特性 is utilized to ensure that the LED only lights up in response to sound.

💡Condenser Microphone

A condenser microphone is a type of microphone that uses a capacitor as its transducing element. In the video, a condenser microphone is used to detect sound. It changes its capacitance based on the sound it receives, which is then sensed by the circuit to control the LED.

💡Resistor

A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In the video, 10 kilo ohm resistors are used to form voltage dividers, while a 270 ohm resistor is used to connect the LED to the positive rail, limiting the current through the LED.

💡Capacitor

A capacitor is a passive two-terminal electrical component that stores electrical energy temporarily in an electric field. In the video, a 0.47 microfarad capacitor is used to filter out excess noise from the op-amp circuit, ensuring that the LED only responds to the intended sound signals.

💡Ohm's Law

Ohm's Law states that the current through a conductor between two points is directly proportional to the voltage across the two points. The video mentions Ohm's Law in the context of explaining series and parallel circuits, which is foundational knowledge for understanding how voltage dividers work in the circuit.

💡Series Circuit

A series circuit is an electrical circuit configuration where the components are connected end-to-end so that there is only one path for the current to flow. In the video, resistors are connected in series to form voltage dividers, which is a common practice in electronic circuit design to control voltage levels.

💡Voltage Regulation

Voltage regulation is the process of maintaining a nearly constant voltage level despite changes in load or input voltage. In the video, voltage regulation is achieved through the use of voltage dividers and the op-amp, ensuring that the LED receives a stable voltage that can respond dynamically to sound signals.

Highlights

Introduction to creating a sound-reactive LED

Explanation of the theory behind the sound-reactive LED

Demonstration of LED turning on with sound

Importance of voltage dividers in the circuit

Detailed explanation of how a voltage divider works

Purpose of multiple voltage dividers in the circuit

Brief review of the operational amplifier (op-amp)

Step-by-step guide to connect the op-amp pins

Formation of a voltage divider with 10 kilo ohm resistors

Role of the feedback resistor in the circuit

Use of a one mega ohm resistor for feedback

Explanation of how a diode drops voltage in the circuit

Placement of the diode for optimal voltage drop

Necessity of a capacitor to filter out noise

Use of a 0.47 microfarad capacitor for noise filtering

Connecting the LED to the circuit

Explanation of why a 270 ohm resistor is used for the LED

Optimal voltage for the circuit operation

Function of a condenser microphone in the circuit

Connection of the condenser microphone to the circuit

Final assembly and completion of the op-amp circuit

Detailed explanation of how the circuit operates with sound

Transcripts

[Music]

[Laughter]

[Music]

hello everyone

in this video we will make a sound

reactive led

we will learn how it works the theory

behind it

and why each component is there so as

you can see

as i'm talking the led is turning on

so i hope you enjoy this video and if

you do please leave a thumbs up and

subscribe to my channel

so as you may have noticed in this

circuit diagram

there are a lot of voltage dividers

so for example this right here is a

voltage divider

and this right here is a voltage divider

a voltage divider

is where there are two resistors in

series

just like this and if you don't know

what series in parallel is

you can check out my video on ohm's law

in the description

so we have here the 10 kilo ohm resistor

is like this

it takes positive voltage and negative

voltage

it brings them together like this and

then it stops at the node right here

and an output is fed off so basically

it takes a regulated voltage combines

the positive and negative together

and then it creates a smaller voltage at

its node right there

there are a lot of these in the circuit

because sometimes

you don't want a certain amount of

voltage and you want it to drop

increase or decrease so that is why in a

lot of circuits that you need to use

these voltage dividers

a quick review on the op-amp

is it's an operational amplifier it

takes two input voltages and inverting

and non-inverting

and splits out an output so guys our

first step is to connect

pin 8 to the positive rail and pin 4 to

the negative rail

after that we want to form a voltage

divider with two 10 kilo ohm resistors

so right here at pin 3 or the

non-inverting

input you want to create a voltage

divider because we want to drop down the

voltage right there

so we take a 10 kilo ohm resistor

and we put it on pin 3 we put that to

the negative rail

and put the other one to the positive

rail just like this

and then pin 8 to the positive row

so next after the voltage divider our

circuit needs a feedback resistor

so what a feedback resistor is it's a

high resistance resistor and it goes on

one of the inputs and one of the outputs

it acts as negative feedback for this

optic

so we're going to take a one mega ohm

resistor

and place it between the inverting input

and the output

so like this we're going to place it on

pin two

which is the inverting input and we're

going to place it

also on pin one

we for our led to be sound reactive

and turn off when there is no um

sound coming we need something to drop

the voltage

and a diode is a really good candidate

to do that

this is because if current runs through

a diode

what happens is the voltage drops a lot

because of its characteristics as you

can see in the video

in the description about diodes so we're

going to place this cathode

facing the output so the cathode

is this little line right there so we're

going to place it

like this so we place this cathode

on the output and its anode out in the

distance

so you can connect it to an led

so there because this lm350 op-amp once

you receive voltage divider and all the

signals coming at it

it releases so much extra voltage that

we do not need

so this diode drops it as heat

our next thing is that we need capacitor

to filter out

excess noise that are coming from here

so it doesn't get confused this little

op-amp

so we're going to use a 0.47 microfarad

capacitor

to do this so we're gonna take a wire

and place it on the inverting input or

pin two

just like this then we're gonna take the

capacitor

and place one of its pins on that

then we're going to form a voltage

divider using 10k resistors again

as we take the 10 kilo ohm resistor and

place the other side of the capacitor

this one one to the negative

and one to the positive just like this

so if you may have noticed that i um

took out the 10 kilometer sister for a

minute

and i put it back right there so our

next step

is to take an led in place it's negative

or it's cathode on the diode

and take its anode or its positive

and connect it to the positive rail and

use a resistor to do this

so you can use a 270 ohm resistor

because this circuit works best on 5

volts of battery

because if you use a 9-volt battery

supply

sometimes it doesn't pick up that much

sound

and it um the led stays on because of so

much

voltage and there's not enough to get

dropped by this

diode denser microphone if you don't

know

a condenser microphone changes its

capacitance based on the sound it

receives

so for example if it receives a lot of

sound the capacitance

increases and gets sensed by the circuit

if there's no sound

then it won't get sensed by the circuit

and then

the led will turn off it's a wire

connecting

to the negative rail so we connect the

condenser mics negative over there

and it's positive to the side of the

capacitor where the voltage divider was

so right over here now the sound and the

signals can travel all around the

circuit

so now our m358 op-amp circuit is

complete

so how the circuit works is um sound

gets traveled into this condenser mic

the condenser rack is getting powered

right here

then the signal travels all the way over

here and gets

regulated and the voltage just gets

smaller and

gets better because of this voltage

divider right here

after that it travels out the node over

here you can follow this arrow

and then it travels to the 0.47

microfarad capacitor to get filtered

then right here it comes down here

signal or the electrons or

current and let me just write that down

i stands for current by the way so then

it goes right here and this acts as a

feedback resistor for this op-amp

so then it goes through the feedback and

out in the output

and this inverting um non-inverting

input actually

basically acts as just a another output

so the comparators can have two inputs

because it doesn't make sense if you

have one input because then you just

have that as an output

so this right here acts as another input

then it goes right here

and this diode drops the voltage by

about three volts

and then it goes to this led to get

power

you