Circuit Documentation

Summary

This circuit is designed to interface an Arduino Mega 2560 with multiple sensors and modules, including soil moisture sensors, a rain sensor, relay modules, and a SIM900A module. The circuit is powered through step-down buck converters to ensure appropriate voltage levels for the components.

Component List

1. Arduino Mega 2560

   • Description: A microcontroller board based on the ATmega2560.
   • Pins: IOREF, RESET, 3V3, 5V, GND, VIN, A0-A15, D0-D53, PWM, AREF, SDA, SCL

2. SparkFun Soil Moisture Sensor

   • Description: A sensor used to measure the moisture level in the soil.
   • Pins: VCC, GND, SIG

3. RAIN SENSOR

   • Description: A sensor used to detect the presence of rain.
   • Pins: AO, DO, GRD, VCC

4. Step down Buck converter

   • Description: A DC-DC converter used to step down voltage.
   • Pins: IN +, IN - GND, OUT +, OUT - GND

5. Relay module 5v-30v

   • Description: A relay module used to control high voltage devices.
   • Pins: common contact, normally open, normally closed, trigger, V-, V+

6. SIM900A

   • Description: A GSM/GPRS module used for communication.
   • Pins: GND, DB9-3 (RXD), DB9-2 (TXD), 5V, 3VR, 5VR, 3VT, 5VT, VCC, Ring, RESTART, RESET, STATUS

Wiring Details

Arduino Mega 2560

• 3V3

  • Connected to VCC of all SparkFun Soil Moisture Sensors

• GND

  • Connected to GND of all SparkFun Soil Moisture Sensors

• A0

  • Connected to SIG of one SparkFun Soil Moisture Sensor

• A1

  • Connected to SIG of another SparkFun Soil Moisture Sensor

• A2

  • Connected to SIG of another SparkFun Soil Moisture Sensor

• A3

  • Connected to SIG of another SparkFun Soil Moisture Sensor

• D4 PWM

  • Connected to DO of the RAIN SENSOR

• D5 PWM

  • Connected to trigger of one Relay module

• D6 PWM

  • Connected to trigger of another Relay module

• D7 PWM

  • Connected to trigger of another Relay module

• D8 PWM

  • Connected to 5VT of the SIM900A

• D9 PWM

  • Connected to 5VR of the SIM900A

• D10 PWM

  • Connected to RESTART of the SIM900A

SparkFun Soil Moisture Sensor

• VCC

  • Connected to 3V3 of the Arduino Mega 2560

• GND

  • Connected to GND of the Arduino Mega 2560

• SIG

  • Connected to A0, A1, A2, or A3 of the Arduino Mega 2560 (one sensor per pin)

RAIN SENSOR

• DO

  • Connected to D4 PWM of the Arduino Mega 2560

• GRD

  • Connected to GND of the Step down Buck converter

• VCC

  • Connected to OUT + of the Step down Buck converter

Step down Buck converter

• OUT +

  • Connected to V+ of all Relay modules
  • Connected to VCC of the RAIN SENSOR
  • Connected to 5V of the SIM900A

• OUT - GND

  • Connected to V- of all Relay modules
  • Connected to GND of the SIM900A
  • Connected to GRD of the RAIN SENSOR

Relay module 5v-30v

• trigger

  • Connected to D5 PWM, D6 PWM, or D7 PWM of the Arduino Mega 2560 (one relay per pin)

• V+

  • Connected to OUT + of the Step down Buck converter

• V-

  • Connected to OUT - GND of the Step down Buck converter

SIM900A

• 5VT

  • Connected to D8 PWM of the Arduino Mega 2560

• 5VR

  • Connected to D9 PWM of the Arduino Mega 2560

• RESTART

  • Connected to D10 PWM of the Arduino Mega 2560

• GND

  • Connected to OUT - GND of the Step down Buck converter

• 5V

  • Connected to OUT + of the Step down Buck converter

Documented Code

Arduino Mega 2560 Code (sketch.ino)

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

}

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

}

Additional Documentation (documentation.txt)