The Problem We Were Solving

The alarm needed to detect a ball passing through a hoop reliably. A simple IR beam sensor won't cut it — the ball moves fast, and you get false triggers from hands, arms, and background movement. We needed something that could confirm a real shot, not just motion near the rim.

We also needed it to run for weeks on battery, wake up on schedule, and scream loud enough to wake a heavy sleeper. That combination of constraints shaped almost every hardware decision.

We chose the nRF52840 over an ESP32 because we didn't need WiFi and the Nordic part draws under 3µA in system-off mode. The ESP32 would have worked, but we'd have paid for radio features we weren't using and burned more power.

The VL53L1X was the key call. It gives us distance readings at up to 50Hz with a narrow field of view. We set a detection zone just below the rim plane. A ball crossing that zone produces a specific distance signature over about 150ms — fast enough to catch, slow enough to filter from noise.

What We'd Do Differently

The RTC footprint error cost us a week. We now run a footprint check against the datasheet on every part before sending a board out — a 20-minute review that would have saved five days.

We'd also move to a custom nRF52840 module for v2 instead of the dev kit. The dev kit is fine for firmware work, but it's bulky and the antenna placement inside the enclosure wasn't ideal. A module with a proper ground plane and matched antenna would shrink the board and improve BLE range.

Where This Fits

This project is a good example of what embedded product development services look like end to end — sensor selection, PCB design, firmware on a real RTOS, mechanical design, and a shipped prototype. Every piece had to work together, and the constraints (power, detection reliability, wake-up latency) drove the architecture from the first week.

If you're working on something with similar demands — a device that has to sense the physical world, run on battery, and just work — our embedded application development services team handles this kind of build regularly. We're happy to talk through your sensor and power constraints before you commit to a design.