README.md

Hot Tub Water Quality Sensor

• Battery powered ORP, pH sensor for Hot Tub/SPA
• Free Chlorine/Total Bromine estimate from pH and ORP values
• Home Assistant Integration
• pH ATC (Automatic Temperature Compensation)
• 2024 update: Added Solar Panel

Hardware

• UM FeatherS2 ESP32 board from here
• 2500 mAh
• Atlas Scientific Gravity Analog ORP and pH Kits
• Enclosure: DS-AT-0811-S
• 2x100 kΩ resistors for battery monitoring (optional)

Optional Solar Panel Components

• Adafruit Universal USB / DC / Solar Lithium Ion/Polymer charger - bq24074
• 3.5mm / 1.1mm to 5.5mm / 2.1mm DC Jack Adapter
• Small 6V 1W Solar Panel
• JST-PH 2-pin Jumper Cable

Wiring

• Diagram

Firmware

• micropython. OTA & Logging over MQTT
• deep (50µA) & light (7mA) sleep
• Build instructions
• Code

FC (Free Chlorine) ppm Model

Predict Free Chlorine/Total Bromine ppm from pH and ORP sensors.

• Data source: https://jenfitch.com/free-chlorine-orpmv-vs-ph-new/

Build the model: fc_model.ipynb.

Prebuilt model:

• model_fc.h5: model for predicting FC from ORP/pH

Basic script to load and run the model. usage:

python3 predict.py  model_fc.h5 ORP_VALUE PH_VALUE

Convert tflite model to tflite-micro

make gen

Execute tflite-micro model on Native Hardware

make tflite
make
./a.out