LAPCOUNTER / CURRENT BUILD 0.2 / OCTOBER 17, 2026

Build the counter.
Skip the contractor budget.

A modulated infrared crossing gate makes the lap decision. A simple wearable receives the stored total, displays it and vibrates. Off-the-shelf boards, with firmware and wiring supplied.

Open complete build guide ↗Download firmware + engineering ↓Itemized parts list ↓
Optical emitter and receiver across one lane, with absolute count updates sent to the wearable
Parts, cases and mounts$142.05Published core prices and labeled hardware allowances.
Total planning budget$211.96Includes shipping, estimated tax and 20% contingency.
Contractor labor budget$0Assembly tools and hired hands-on labor are extra.

Target-compiled firmware. Physical testing still ahead.

Firmware is supplied for the emitter, receiver gate and wrist unit. No target board is connected; nothing has been flashed or field-tested. The guide includes wiring, flashing, recovery, logs and the physical acceptance tests.

Use one runner in a controlled lane. The gate counts anyone who interrupts its beam. It cannot identify runners, determine direction or prove a full circuit.

Test the optical link before spending more.

Three boards and the two optical modules cost $37.60 before freight and tax. Use reused USB power for the first daylight and lane-width experiment. Add the wrist display, haptics, batteries and cases after that check.

Emitter UF2 ↓Gate UF2 ↓Wrist UF2 ↓Verification record ↗
Earlier 0.1 proximity counting and contractor estimates are superseded by this build. Retained for reference: original interaction demo and original concept report. No parts have been purchased.