Hi friends today let's see about smoke detector
Many of you went malls in malls mostly you can see this device called smoke detector it will detect the smoke and turn on sprinkler and stop the fire.
But in this project that is a slight change instead of sprinkler led light and piezo will work .
Let's see how to make a smoke detector.

Supplies

Arduino
Jumper wires
Gas sensor
Three LEDs
One piezo and
Bread board

Step 1: Smoke Detector

A smoke detector is a device that senses smoke, typically as an indicator of fire. Commercial security devices issue a signal to a fire alarm control panel as part of a fire alarm system, while household smoke detectors, also known as smoke alarms, generally issue a local audible or visual alarm from the detector itself or several detectors if there are multiple smoke detectors interlinked

Step 2: Arduino

Arduino is an open-source electronics platform based on easy-to-use hardware and software. Arduino boards are able to read inputs - light on a sensor, a finger on a button, or a Twitter message - and turn it into an output - activating a motor, turning on an LED, publishing something online. You can tell your board what to do by sending a set of instructions to the microcontroller on the board. To do so you use the Arduino programming language (based on Wiring), and the Arduino Software (IDE), based on Processing.

Step 3: Gas Sensor

A gas sensor is a device which detects the presence or concentration of gases in the atmosphere. Based on the concentration of the gas the sensor produces a corresponding potential difference by changing the resistance of the material inside the sensor, which can be measured as output voltage.

Step 4: Bread Board

A breadboard is a construction base for prototyping of electronics. Originally the word referred to a literal bread board, a polished piece of wood used for slicing bread. In the 1970s the solderless breadboard (a.k.a. plugboard, a terminal array board) became available and nowadays the term "breadboard" is commonly used to refer to these.

Step 5: Piezo

In simplest terms, a piezo buzzer is a type of electronic device that's used to produce a tone, alarm or sound. It's lightweight with a simple construction, and it's typically a low-cost product.

Step 6: Jumper Wires

A jump wire (also known as jumper wire, or jumper) is an electrical wire, or group of them in a cable, with a connector or pin at each end (or sometimes without them – simply "tinned"), which is normally used to interconnect the components of a breadboard or other prototype or test circuit, internally or with other equipment or components, without soldering.

Step 7: LEDs

A light-emitting diode (LED) is a semiconductor light source that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (corresponding to the energy of the photons) is determined by the energy required for electrons to cross the band gap of the semiconductor.White light is obtained by using multiple semiconductors or a layer of light-emitting phosphor on the semiconductor device

Step 8: Let's Gather

Gather all the things what we saw until now

Step 9: Place Arduino and Bread Board

Keep the Arduino wherever you want and place the bread board also near to it and connect the positive charge of 5 v and negative charge of gnd (ground) to positive and negative terminal of the bread board.

Step 10: Place the LEDs and Piezo Too

Place the piezo and three LEDs in the bread board as shown in the picture .
Also connect the positive terminal (anode) of all the LEDs and piezo to digital pin of the Arduino.
Connect negative terminal (cathode) to bread board's negative terminal as shown in the picture.

Step 11: Connect the Gas Sensor

The gas sensor is very important in this you have to place it any where near the Arduino.
Connect the a1,h1,a2 terminal of gas sensor to bread board
Also connect the particular series of wire with positive terminal of the bread board.
Connect the B2 and H2 of the gas sensor with bread board's negative terminal.also connect the b1 terminal of the gas sensor to any one of the analog pin of the Arduino.

Step 12: Let's Code

That's all designs let's jump into programming.
First we have say the system to print the readings given by gas sensor in serial monitor.
Next
By the next lines we have to insist the smoke detector to make blink green light if the smoke is not near .
It denotes safe
The if the smoke is moderately near means yellow light will blink and piezo will give sound somewhat
The we insist that if the smoke is very closer the sound need to be very high and red led should blink.