Soil Moisture Sensor
The Picapot PS100 sensor provides consistent soil moisture measurements that can serve as a reference for triggering watering cycles. The plants' health will greatly benefit, and water waste will be reduced.
This resistive, temperature-compensated sensor uses carbon fiber probes and is encased in a high-density silicone shell.
With no parts exposed to oxidation, electrolysis, or erosion, this sensor is ideal for continuous soil-moisture monitoring in wet soil.
PS100 implements the DS18B20 sensor from Maxim Integrated as a precise temperature sensor and as a reliable data server.
Every 4 seconds, PS100 requests a new 12-bit temperature conversion from the
internal DS18B20, then measures soil moisture and writes the result to the DS18B20
scratchpad memory.
The user can retrieve temperature and soil moisture values from the DS18B20
scratchpad, a 4-byte memory, by sending the standard "Read Scratchpad" command
[0xBE].
You can find all the technical details in the datasheet:
picapot-ps100-sensor-datasheet.pdf (PDF, 609.81 KB)
You can find an example of the Arduino UNO and PS100 connection at:
https://github.com/Ipposnif/PS100Test
Sensor Integration with the Controller
The PS100 sensor is fully compatible with the HT328 Controller. Connect the sensor’s three wires, then go to the controller Options screen and select Sensor → Picapot.
Three functions depend on a 1-wire temperature/soil-moisture sensor:
- Moisture Limit: Skip watering if the soil moisture level is greater than the value specified by the user. This functionality is really important because it prevents overwatering when the soil is already humid. It requires a soil-moisture sensor.
- Skip Ice: Skip watering if the temperature is lower than 5 degrees Celsius. This functionality protects the plants and the valve from frost. It requires a temperature sensor.
- Heat Boost: When the maximum recorded temperature of the day is greater than the value specified by the user, watering duration is increased by a specified percentage. It requires a temperature sensor.
All three functions can be achieved with the PS100 sensor.
DS18B20 Wired Temperature Sensor
As a partial alternative to the PS100, you can use an external waterproof DS18B20 sensor. In this case, only functions 2 and 3 are available.
If no external sensor is connected, the controller uses its built-in temperature sensor. But an external sensor is always recommended, as measuring the soil directly provides a more meaningful temperature reading than measuring the air inside a metal enclosure.
