This repository contains the PCB design files to interface the popular Irrometer 200SS soil moisture sensor and read the equivalent soil tension in Frequency.
The RT9193-33GB IC is an LDO used to convert 5V to 3.3V for LMC555 and 74HC4052D ICs. Using the ENABLE pin of the LDO, we can control the poweron-off of the circuit. It is a LDO with drop voltage of around 0.3V. SO your board supply VCC can go as low as 3.6V and the circuit will still function.
The Frequency to KPa (CB) conversion is as below:
kPa = 0 for Hz > 6430
kPa = 9 - (Hz - 4600) * 0.004286 for 4330 <= Hz <= 6430
kPa = 15 - (Hz - 2820) * 0.003974 for 2820 <= Hz <= 4330
kPa = 35 - (Hz - 1110) * 0.01170 for 1110 <= Hz <= 2820
kPa = 55 - (Hz - 770) * 0.05884 for 770 <= Hz <= 1110
kPa = 75 - (Hz - 600) * 0.1176 for 600 <= Hz <= 770
kPa = 100 - (Hz - 485) * 0.2174 for 485 <= Hz <= 600
kPa = 200 - (Hz - 293) * 0.5208 for 293 <= Hz <= 485
kPa = 200 for Hz < 293
You can achieve this in the microcontroller program using "If" conditions. The conversion reference is from the datasheet of SMX circuit (https://www.emesystems.com/smx/documents/SMX_2018.pdf)
The attached Arduino code is tested successfully with ATmega328p and STM32F103 microcontrollers. Same can be adapted to PIC controllers and others as well.
Read more here - https://medium.com/fasal-engineering/a-low-cost-circuit-to-read-from-multiple-watermark-irrometer-200ss-sensors-a4c838da233a
MIT
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