Adafruit IoT platform is used to monitor the water-pump’s status online. Data pin D8 of IC2 is connected to pin D0 of NodeMCUmodule (Board1) to provide the motor on/off status on a remote computer or smartphone over cloud. The heart of the IoT system is NodeMCU ESP32/8266 Wi-Fi module. If optional sensor is used at J1 in the transmitter, LED2 indicates the optional motor’s status. LED3 is for power on indication, LED4 for RF signal, and LED1 for water-pump’s motor on status. Data pin D8 of IC2 drives the relay through transistors T2 and T3.ĭiode 1N4007 (D2) connected in reverse bias mode is used to protect the circuit against voltage spikes during switching on/off of the water-pump. Decoder HT12D, with address pins A0 though A7 connected to ground, receives the serial data at its pin 14 from RX1. The signal from transmitter is received by 433MHz receiver module RX1. This receiver also operates off a 5V DC supply. The receiver comprises 433MHz RF receiver module (RX1), decoder HT12D (IC2), two BC317 transistors (T2 and T3), a 5V single-changeover relay (RL1), and NodeMCU (Board1). J1 is used for optional sensor input for an optional motor in the receiver circuit. The modulated ASK RF signal from DOUT is transmitted by TX1 module at 433MHz frequency. Encoder IC1 receives active-high signal at pin 10 (AD8) from collector of T1 and generates serial data at pin 17 (DOUT) with its address pins A0 through A7 connected to ground. When soil moisture in the field goes below the threshold level, the sensor produces active low (0V) signal, which goes to the base of inverting transistor T1. Threshold level of the soil moisture can be set using the in-built pot in soil sensor module.
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