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References: Sensors and Electronics Hardware

  1. Glass electrode - Wikipedia - Explains the electrochemistry of the glass pH electrode, including the ion-selective glass membrane, reference electrode, and Nernst equation governing the millivolt output calibrated to pH units.

  2. Peristaltic pump - Wikipedia - Covers peristaltic pump design using rotating rollers to compress flexible tubing; explains why this pump type is preferred for dosing nutrient concentrates and pH adjustment chemicals in hydroponic automation.

  3. Operational amplifier - Wikipedia - Detailed treatment of op-amp circuits including voltage followers, summing amplifiers, and difference amplifiers used in sensor signal conditioning for pH electrodes, EC probes, and low-level analog sensors.

  4. MicroPython for the Internet of Things - Charles Bell - Apress - Hardware chapters cover DS18B20 one-wire wiring, DHT22 signal protocols, relay module drive circuits, pH electrode ADC interfacing, breadboard prototyping, and waterproof enclosure requirements for wet environments.

  5. Programming the Raspberry Pi Pico/W - Simon Monk - McGraw-Hill - Practical sensor chapters cover analog voltage reading via ADC, voltage divider design, I2C sensor libraries, and the wiring conventions for connecting commercial sensor modules to microcontroller boards.

  6. MicroPython: DS18X20 Library - MicroPython.org - Official documentation for the DS18B20 one-wire temperature sensor library, including wiring diagram, onewire bus initialization, and temperature conversion timing relevant to hydroponic water temperature monitoring.

  7. MicroPython: DHT Library - MicroPython.org - API reference for reading DHT11 and DHT22 temperature and humidity sensors from MicroPython; covers timing requirements, error handling, and data parsing for reliable readings.

  8. Raspberry Pi: GPIO and Electronics - Raspberry Pi Foundation - Hardware reference for GPIO electrical specifications, voltage levels, current limits, and safe wiring practices applicable to relay modules, sensors, and actuators in hydroponic control systems.

  9. Khan Academy: Electrical Circuits - Khan Academy - Physics of Ohm's law, voltage dividers, and circuit analysis foundational to designing sensor input conditioning circuits, pull-up resistors, and relay drive circuitry.

  10. Real Python: Reading Sensors with Python - Real Python - Tutorial on interfacing sensors with Raspberry Pi using Python; the GPIO and I2C programming patterns translate directly to MicroPython sensor code on Pico and ESP32 nodes.