Circuit Documentation

Summary

The circuit in question is designed to interface various gas sensors (MQ-4, MQ-5, MQ-6, and MQ-7) with an ESP8266 NodeMCU microcontroller for gas detection purposes. Additionally, the circuit includes a DHT11 temperature and humidity sensor, a buzzer, an LED, and an LCD display (20x4 with I2C interface) for user interaction and feedback. The ESP8266 NodeMCU serves as the central processing unit, reading sensor data, controlling the buzzer and LED, and displaying information on the LCD.

Component List

ESP8266 NodeMCU

• Microcontroller with WiFi capability
• Pins: D0-D8, RX, TX, A0, RSV, SD3, SD2, SD1, CMD, SD0, CLK, EN, RST, VIN, 3V3, GND

MQ-4 Gas Sensor

• Methane (CH4) gas sensor
• Pins: A0, D0, GND, VCC

MQ-5 Gas Sensor

• LPG, natural gas, and coal gas sensor
• Pins: Analog out, Digi Out, GND, VCC

MQ-6 Gas Sensor

• LPG, butane gas sensor
• Pins: A0, DO, GND, VCC

MQ-7 Gas Sensor

• Carbon monoxide (CO) gas sensor breakout module
• Pins: AO, DO, GND, VCC

DHT11 Temperature and Humidity Sensor

• Digital sensor for ambient temperature and humidity
• Pins: DATA, GND, VCC

Buzzer

• Audible signaling device
• Pins: PIN, GND

LED: Two Pin (red)

• Red indicator light
• Pins: cathode, anode

Lcd 20x4 i2c

• Alphanumeric LCD display with I2C interface
• Pins: GND, 5v, SCA, SCL

Wiring Details

ESP8266 NodeMCU

• D0 connected to MQ-7 Breakout DO
• D1 connected to MQ-4 D0
• D2 connected to MQ-5 Digi Out
• D3 connected to Lcd 20x4 i2c SCL
• D4 connected to Lcd 20x4 i2c SCA
• D7 connected to DHT11 DATA
• D8 connected to Buzzer PIN and LED cathode
• GND connected to Buzzer GND, LED anode, MQ-4 GND, MQ-5 GND, MQ-6 GND, MQ-7 Breakout GND, DHT11 GND, Lcd 20x4 i2c GND
• A0 connected to MQ-6 A0
• VIN connected to MQ-4 VCC, MQ-5 VCC, MQ-6 VCC, MQ-7 Breakout VCC, DHT11 VCC, Lcd 20x4 i2c 5v

MQ-4 Gas Sensor

• A0 (Not connected)
• D0 connected to ESP8266 NodeMCU D1
• GND connected to common ground
• VCC connected to ESP8266 NodeMCU VIN

MQ-5 Gas Sensor

• Analog out (Not connected)
• Digi Out connected to ESP8266 NodeMCU D2
• GND connected to common ground
• VCC connected to ESP8266 NodeMCU VIN

MQ-6 Gas Sensor

• A0 connected to ESP8266 NodeMCU A0
• DO (Not connected)
• GND connected to common ground
• VCC connected to ESP8266 NodeMCU VIN

MQ-7 Gas Sensor

• AO (Not connected)
• DO connected to ESP8266 NodeMCU D0
• GND connected to common ground
• VCC connected to ESP8266 NodeMCU VIN

DHT11 Temperature and Humidity Sensor

• DATA connected to ESP8266 NodeMCU D7
• GND connected to common ground
• VCC connected to ESP8266 NodeMCU VIN

Buzzer

• PIN connected to ESP8266 NodeMCU D8
• GND connected to common ground

LED: Two Pin (red)

• cathode connected to ESP8266 NodeMCU D8
• anode connected to common ground

Lcd 20x4 i2c

• GND connected to common ground
• 5v connected to ESP8266 NodeMCU VIN
• SCA connected to ESP8266 NodeMCU D4
• SCL connected to ESP8266 NodeMCU D3

Documented Code

No code has been provided for the microcontroller. The documentation of the code would typically include a description of the functionality, setup, and loop routines, along with any functions or libraries used to interface with the sensors and output devices. Since no code is available, this section cannot be completed.