2024

[031] MULTIPLEXED RESISTIVITY MEASUREMENT SYSTEM

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Measuring resistivity across multiple points without manually rewiring between each measurement — that was the goal.

Channel selection is handled through I/O expanders and multiplexing logic. Contacts are made with pogo pins: repeatable, quick to install, no soldering required. The STM32F030 sequences the measurements, does basic signal processing, and talks to the host over USB-C for both power and data.

A well-designed lab tool: compact, portable, and capable of automating a task that would otherwise be slow and prone to human error.

[030] POWER CONVERTER WITH RS485 TELEMETRY

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A DC power conversion controller in the few-hundred-watt range, built around an STM32F334 — a micro that’s genuinely well-suited to power applications thanks to its high-resolution timers and ADCs.

The firmware synchronizes ADC sampling to measure bus voltage and current, applies filtering, and computes instantaneous power for regulation and monitoring. MPPT control closes the loop by adjusting the boost converter’s operating point through PWM duty cycle updates (~48 V class). Soft-start, duty limiting, and fault-triggered shutdown are all handled natively.

On the protection side, a dump load path can be activated to clamp bus overvoltage and safely absorb excess energy. Telemetry goes out over Modbus/RS485: measurements, operating state, fault codes — all exposed for supervision.

[029] WI-FI ROUTER WITH AC AND BATTERY POWER

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A compact ESP32-based router powered from 230 VAC mains, with a Li-Ion backup battery. When the mains fails, the battery takes over — transparent to the network.

The firmware sets up the ESP32 in a multi-role Wi-Fi configuration (uplink + local access point), handles link monitoring, automatic reconnection, and basic system supervision (watchdog, status reporting). The battery section covers safe charging, protection, and voltage monitoring to prevent undervoltage operation and keep source switching predictable.

Not the most technically complex project, but exactly the kind of device that’s genuinely useful to have around when connectivity can’t afford to drop.