Project Description
The power stage of my transformer-based Li-ion home UPS is already proven in the lab—what I still need is the brains. I’m looking for a seasoned embedded developer who can build clean, modular firmware for an STM32 that will bring the unit to life and withstand regulatory scrutiny.
Scope of work
• Battery management: implement reliable CC/CV charging logic and tight thermal protection. Per-cell cut-off at specific voltages can remain configurable for later revisions, but the two listed functions must be rock-solid in this release.
• Inverter section: the first priority is crisp, low-distortion SPWM generation that tracks load changes smoothly. Overload and short-circuit handling already exist in hardware; firmware hooks to report and latch these events will be part of your task.
• Protections: code hooks for over/under-voltage, over-current, and over-temperature must feed a unified fault handler so audits can trace every trip event.
• LCD user interface: design a custom graphical interface (not just a status line) that presents runtime data, charging state, and any active faults.
• Documentation: every module needs concise in-code comments plus a separate design note explaining algorithms, interrupt use, and test points so a third-party auditor can follow the logic without reverse-engineering.
Deliverables
1. Complete STM32CubeIDE project with source, linker scripts, and any middleware you add.
2. PDF/Markdown design document covering architecture, state charts, protection thresholds, and test procedures.
3. Remote support while I flash, power-up, and validate on the actual hardware during the 4–6 week development window.
Acceptance criteria
• UPS must switch seamlessly between mains and battery with <20 ms break.
• Output THD <5 % at rated load verified via oscilloscope capture.
• Charger stops at the programmed voltage and responds to over-temperature within one second.
• No watchdog resets or hard faults during an 8-hour soak test.
I’ll provide full schematics, pin maps, and current prototype measurements the moment we start. Looking forward to seeing how you can turn this hardware into a dependable, audit-ready product.
Milestone 1 (₹15k–₹20k):
STM32 setup + battery cutoff logic (3.65V/2.8V)
Milestone 2 (₹20k–₹25k):
SPWM inverter control + protections (over‑voltage, under‑voltage, overload, thermal)
Milestone 3 (₹15k–₹20k):
LCD integration + final documentation (audit‑ready)