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Hardware: Overview
The hardware of the project comprises of three major parts:
- Seeed Studio Wio Node.
- Soil moisture sensor.
- Power supply.
Seeed Studio Wio Node is used as the brains of the hardware. It is based on Espressif ESP8266 WROOM 2 module with two Grove connectors. The ESP8266 WROOM 2 module integrates a ESP8266EX SoC which is based on Tensilica L106 32-bit RISC processor.
Any analog soil moisture sensors can be used for this project considering the following factors:
- The sensor must be adapted to be connected to the WROOM 2 module with the Grove connector.
- The sensor must be able to be powered by the VCC pin of the Grove connector.
- The analog voltage reference of the sensor must be able to be provided by the VCC pin of the Grove connector.
Initially the Grove Moisture Sensor was used for the project as it was readily compatible with the Grove connector. One major problem with this sensor is that the sensor is of resistive type with copper coating on the legs which is subject to corrosion. A better alternative is a capacitive type of sensor. The project was also tested with this DFRobot Capacitive Soil Moisture Sensor. Which requires connector adaptation to be able to connect the sensor to the Grove connector of the Wio Node.
The hardware can be powered by both the JST connector and the Micro USB connector of the Wio Node. The Wio Node incorporates LiPo charging circuitry. If a LiPo battery is connected to the JST connector then connecting power to the Micro USB port will start charging the battery from the power provided by the Micro USB port. The system is tested with a single cell 18650 LiPo battery.