Gate opener
My sister has epilepsy and lives alone in a flat in Malmö. If she has a seizure, family arriving to help have no way in. The building's street gate and stairwell door open only from a Ritto TwinBus intercom handset on her wall, and there's no way to fit a key box to shared gates. Gate opener sits next to the handset, drives a PC817 optocoupler across the door-open button from an ESP32-C3, and hosts a single-page web app on the LAN so family can tap themselves in from a phone. No cloud, no protocol reverse engineering, and nothing on the intercom modified. The signal crosses the two circuits as light.
Log entries
| Ref | Date | Entry |
|---|---|---|
| LOG-01 | 2026-07-26 | An optocoupler across my sister's intercom button Why this exists, how an ESP32-C3 and a PC817 press the door-open button with light, and the design choices that make sure a stuck-open building entrance is never a failure mode. |