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How Sound Sensor Works, How Proximity Sensor Works

In my ARDUINO projects I will be using different types of sensors as per the specific requirements, in this article I will be going in depth on 2 types of sensors i.e How Sound sensor works and How Proximity Sensor Works

How Sound sensor works

how sound sensor works
Image of Sound sensor

How Infrared sensor works

image of infrared type proximity sensor

If you are Arduino Project enthusiast then definitely you might have seen or used this components in any of your projects, these are called sound sensor/sound detection sensor(first image) and Infrared sensors(second image). I will show you how these sensors works in detail along with it’s principle of working, Circuits and description of each components and their functions

Have you ever thought across how this sound detection sensor works?

The Principle of working is similar to human ears, in our case when sound is emitted by any source in audible frequency range it gets picked up by our Eardrum which causes it to vibrate and hence we can feel sound(this is simplest explanation), but in case of sound sensor Diaphragm vibrates and serve as ears to ARDUINO!

Parts used in sound sensor

Electret condenser microphones(pin type)

W104 potentiometer

LM 393 Operational amplifier

Sound detection LED indicator

Power indicator LED

4 Resistor and 2 SMD LED’s

Now let’s go in depth to see how actually each part contribute to overall functioning of sound sensor

Working of Condenser microphone

how sound sensor works circuit

When sound waves are emitted by any audio source for example music from speaker, human voice or sound from vehicle the diaphragm which is one of the part inside mic vibrates, As a result of vibration capacitance changes

So a small voltage is produced because of changes in distance between diaphragm(front plate) and back plate

These 2  plates are separated by spacer

The voltage change varies as per the intensity of sound(shown as arrows in above image) which hits diaphragm

These output signal is of very low strength and hence these low voltage signals needs to be amplified

For the purpose of amplification amplifier is used

Amplifier picks up low strength signals and amplify to signals which is detectable

LM 393 Operational amplifier Pin diagram

how sound sensor works amplifier
Pin out of LM393

Pin1Output 1
Pin2Inverting input
Pin3Non inverting input
Pin5Non inverting input
Pin6Inverting input
Pin7Output 2
output pins

LM 393 Operational amplifier features

Input voltage2v DC to 36v DC
Differential input voltagePower supply voltage
Input bias current25 nA
Input offset current5.0 nA
Input offset voltage5v mV
Lead temperature2600C

W104 potentiometer

This is a trimmer potentiometer with 100kOhms value used for tuning, here by turning the knob with the help of small screw on top of potentiometer sensitivity of condenser microphone can be adjusted

Clockwise turn of screw leads to more sensitivity

Counter clockwise turn for less sensitivity

how sound sensor works potentiometer
Potentiometer closeup W104

Output and input pins of sound sensor

A0 connects to analog pin in Arduino

Gnd/G for negative power supply

+ for Positive power supply (5v supply)

D0 connects to digital pin in Arduino


Sensor Module available in very less price and Easy to use


Only detects sound presence and Can’t recognize frequency


I have used this sensor in making multiple Arduino projects to name few music reactive ARGB lights, voice controlled lights and many more

How infrared sensor works

Infrared sensor is an optoelectronic component used to detect obstacles, hence  the use of this sensor is used in making obstacle sensing projects such as obstacle avoiding robots

Principle of working

how ir sensor works
infrared sensor working principle

Infrared transmitter transmits IR signals when board is supplied with power

In the process of transmission if it detects any obstacles in the path those signals get reflected back

This will be received by IR receiver

The received signals will be having low strength and hence to amplify the signals Op-amp is used

The sensitivity can be increased or decreased with the help of trimmer potentiometer attached to board

Turn the screw to vary the sensitivity

Note: Maximum range of this sensor is 20cm, it means it can detect object at the max distance of 20cm and this distance can be lowered by spinning potentiometer

For example: if you are making obstacle avoidance robot and if u want your robot to change its direction when it finds an object in the range of 10cm it can be done by turning the knob

IR Sensor module consists of

Infrared transmitter

Infrared receiver

LM358 op amp


Infrared transmitter looks very similar to LED diode but in case of LED diode visible light is emitted but in IR transmitter infrared light is transmitted(name itself says everything transmitter= transmitting)

Tip to see IR light: The remote control of TV uses IR sensor to send commands to your television, to see the IR light switch on mobile camera and face it towards IR bulb in remote and randomly press any button on remote you can see IR Light! Thank me later if you Didn’t knew this J

Pin diagram of LM358 Operational Amplifier, all the pin i/o is given in table below

how ir sensor works opamp
Pinout of LM358
1st pinOutput 1
2nd pinThreshold 1
3rd pinInput 1
4th pinGND
5th pinINPUT 2
6th pinThreshold 2
7th pinOutput2
8th pinVcc
pin functions


Here the same 3362 potentiometer with 10k ohm is used, same specifications as given in above description

Output pins of Infrared sensor

Out is used for signal output

GND is for negative power supply

Vcc is for positive power supply


Simple to use and Low cost


Limited to 20cm length, hence can’t be used for large applications

Infrared receiver is sensitive to light hence may cause interference


Though the applications are endless to name some

Can be use to make obstacle avoiding car/robot

Can be used to make touchless hand wash liquid dispenser

Used to make IR thermometer, Room lights can be automated using these type of sensors

Video Link

CLICK HERE to check How sound sensor works concept can lead to various amazing projects

These were the principles behind working of IR Sensor and sound detection sensors ,if you have any points to be added to this in case if I missed any let me know in the comments section below


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