Electronics

Wavie has three circuit boards and a sensor module. Their schematics and layouts are in the design files.

Board	What it does
Main board	Runs the instrument
LED array	Carries the three photometer LEDs and their driver
RGB board	Carries the 33 LEDs of the ring
Light sensor	A TSL2591 module facing the LED array across the cell

The main board

Processor	ESP32-S3 with 16 MB of flash and 8 MB of RAM
Wireless	Wi-Fi and Bluetooth Low Energy
Motor drivers	Two TMC2209 stepper drivers, one for the pump and one for the valve
Probe inputs	pH, ORP and dissolved oxygen, each on its own isolated 16-bit converter; salinity; temperature
Expansion	CAN bus transceiver
USB	USB-C, for recovery and development
Power	24 V DC in, regulated on the board to 5 V and 3.3 V

Why the probe inputs are isolated

A pH or ORP electrode produces a tiny voltage from a source with enormous resistance. Stray currents through the tank water, from pumps, heaters or other probes, easily swamp it. Each of the three electrode inputs has its own galvanic isolation, so the probes cannot disturb each other or pick up noise through the main board.

Motors

The two stepper drivers are controlled over a serial link, which lets the firmware set the motor current precisely and read back driver temperature warnings. The valve motor is only powered while it moves, which keeps it cool.

Recovery

If a firmware update ever fails badly, the USB-C port can be used to re-flash the unit from a computer.