Clock v2

Nixie Tube Clock

A custom Nixie tube clock built on an ESP32, written in Rust using the Embassy async framework.

Hardware

• Microcontroller: ESP32
• Display: 6 × IN-14 Nixie tubes
• Driver: 8 × 8-bit shift registers (74HC595) controlling each tube's cathodes
• Power: High-voltage supply (170 V DC) switched by a high-side transistor
• Storage: On-chip flash for timezone data persistence

Features

• NTP time sync — polls nl.pool.ntp.org periodically and maintains an epoch offset
• Timezone awareness — fetches IANA TZif data over HTTP and persists it to flash; handles DST transitions
• Cathode poisoning prevention — every 15 minutes, each digit on every tube is lit for a calculated duration proportional to how little it has been used
• Power window — HV supply is on only between 09:00 and 23:00 local time; the ESP deep-sleeps outside that window
• Presence detection — polls a local presence server; deep-sleeps for 5 minutes when nobody is home
• OTA updates — accepts firmware uploads over a TCP server on the local network

Repository layout

code/
  clock_v2_core/   # no_std library: time, NTP, TZif, cathode-poisoning logic
  firmware/        # ESP32 binary: Embassy tasks, GPIO, network, flash
kicad/             # PCB schematic and layout
ansible/           # Router setup playbook

Building & flashing

# Host unit tests (fast, no hardware needed)
cargo test -p clock_v2_core

# Flash to device (requires ESP32 toolchain and probe)
cd code/firmware
DEFMT_LOG=debug cargo run --release

Secrets (wifi_ssid.txt, wifi_password.txt) are compiled in from plain-text files in code/firmware/ — create them before building.