Circuit Documentation

Summary of the Circuit

This circuit integrates an Arduino UNO microcontroller with a SIM900A GSM module, a relay module, a temperature sensor (LM35), a fan, and power supply modules via micro USB to cable connectors. The Arduino UNO is used as the central processing unit to control the relay based on the temperature readings from the LM35 sensor and to communicate with the SIM900A GSM module. The relay controls the power to the fan, turning it on or off based on the temperature. The SIM900A module allows for GSM network communication, enabling potential features like remote monitoring or control via SMS or voice. The micro USB to cable connectors are used to provide power to the circuit components.

Component List

Arduino UNO

• Microcontroller board based on the ATmega328P
• Provides digital and analog I/O pins
• Can be programmed via USB connection

SIM900A

• GSM/GPRS module
• Capable of sending SMS, making voice calls, and connecting to the internet
• Interfaces with the Arduino via serial communication

Relay Module 5V-30V

• Electromechanical switch that can be controlled by the Arduino
• Used to turn the fan on and off
• Has normally open (NO), normally closed (NC), and common contact (COM) terminals

Temperature Sensor (LM35)

• Precision integrated-circuit temperature sensor
• Outputs an analog voltage proportional to the temperature
• Easy to interface with the Arduino analog input

Micro USB to Cable (2 Pin)

• Power supply connector
• Provides 5V power from a USB port to the circuit

Fan

• 5V DC fan
• Used for cooling based on the temperature sensor reading

Wiring Details

Arduino UNO

• 5V connected to the relay module (normally open) and temperature sensor (LM35) +Vs
• GND connected to the relay module (normally closed) and temperature sensor (LM35) GND
• A0 connected to the temperature sensor (LM35) Vout
• D11 connected to the SIM900A 5VR
• D10 connected to the SIM900A 5VT
• D7 connected to the relay module common contact

SIM900A

• GND connected to the micro USB to cable connector -
• 5V connected to the micro USB to cable connector +
• 5VR connected to Arduino UNO D11
• 5VT connected to Arduino UNO D10

Relay Module 5V-30V

• normally open connected to the temperature sensor (LM35) +Vs and Arduino UNO 5V
• normally closed connected to Arduino UNO GND
• common contact connected to Arduino UNO D7
• trigger connected to the fan 5V and micro USB to cable connector +
• V+ connected to the fan 5V and micro USB to cable connector +
• V- connected to the fan GND and micro USB to cable connector -

Temperature Sensor (LM35)

• +Vs connected to the relay module (normally open) and Arduino UNO 5V
• Vout connected to Arduino UNO A0
• GND connected to Arduino UNO GND

Micro USB to Cable (2 Pin)

• + connected to the SIM900A 5V, relay module V+, and fan 5V
• - connected to the SIM900A GND, relay module V-, and fan GND

Fan

• 5V connected to the relay module trigger and V+
• GND connected to the relay module V-

Documented Code

Arduino UNO Code (sketch.ino)

void setup() {
  // put your setup code here, to run once:

}

void loop() {
  // put your main code here, to run repeatedly:

}

Note: The provided code is a template and does not contain any functional code. It needs to be populated with the logic for reading the temperature sensor, controlling the relay, and interfacing with the SIM900A module.