PM‑S — Showcase
A metronome as an object: the silhouette of a classic pyramid wind‑up unit, but the swinging pendulum is pure RGB light. The whole bar is the display — every lane's subdivisions & accents ride along its length as moving points of light (all meters combined), a printed tempo scale runs up the vertical axis, and a sliding weight sets the tempo just like the mechanical original.
It's a beautiful, glanceable tempo reference for the shelf, the studio, or a shop window: accents glow amber, normal steps cyan, ghosts soft violet, and the pendulum eases to each beat exactly as a weighted rod would. It runs the same grooves as everything else (load any program string), plays the click through a small speaker, and is powered over USB‑C with a second "thru" port to daisy‑chain. There's no power switch — the real unit starts when you lift it from its holder / set it swinging. No instrument I/O; it's a showpiece.
Spec & bill of materials
Rough parts list — a USB‑C‑powered RP2040 display piece driving addressable RGB light. Ballpark one‑off prices (USD); cheaper at volume.
| Part | Qty | ~$ |
|---|---|---|
| Brain | ||
| RP2040 board, USB‑C — e.g. Waveshare RP2040‑Zero | 1 | 4 |
| RGB light | ||
| Addressable RGB LEDs (WS2812B) — a strip down the pendulum bar, ~40 px | 1 | 5 |
| Frosted acrylic diffuser / light‑guide — the glowing pendulum bar | 1 | 3 |
| Audio | ||
| MAX98357A I²S amp + small speaker — the click | 1 | 4 |
| Power & build | ||
| 2× USB‑C (data+power & power‑thru) + PWR LED — daisy‑chain | 1 | 3 |
| Tilt / lift sensor (accelerometer) — starts when lifted from its holder | 1 | 2 |
| Custom PCB (or perfboard) | 1 | 4 |
| Passives, wire | — | 2 |
| Pyramid enclosure — cast/CNC aluminium or hardwood, frosted front panel | 1 | 14 |
| Total (one‑off) | ≈ $41 | |