Master Clock ESP32 Controller Board – Pre-programmed

Replaces the original electromechanical system in analogue school and industrial secondary clocks. Connects to WiFi and synchronises time automatically.

 DEMO and MANUAL here - link opens in new window

Want to give new life to old school or industrial secondary clocks? This pre-programmed ESP32-based controller board replaces the original electromechanics and adds modern WiFi-driven features.

After simple wiring and connecting to your home or office WiFi, the board automatically synchronises with an internet time server (NTP) and keeps accurate time with no manual intervention. All settings are configured conveniently through a web browser – no app installation required.

What the board can do:

• Automatic time synchronisation from the internet (NTP) at a configurable interval
• Hand position backup to Flash memory – after a power failure the clock automatically catches up
• Email notification on power failure or when manual setup is required
• 30 independent bell schedule entries with day, time and duration selection
• Manual alarm – repeating intermittent ring with configurable tone and pause rhythm
• 3 pulse polarity modes for different types of electromagnetic mechanisms
• Web interface in Czech and English, accessible via mDNS (master-clock.local)
• Secured by a secret URL path to the settings page
• Access recovery by double power cycling – no USB cable needed

Outputs are available on four pins (direct and inverted) for maximum compatibility with different switching module types. The bell output has a dedicated pin for connecting a bell or siren.

Included in delivery: detailed user manual in Czech and English, wiring diagram available for download.

Board specification: Arduino-compatible ESP32 clone – Uno D1 R32, 4 MB flash, WiFi + Bluetooth. Can be powered via USB-C or a standard 5–12 V adapter (9 V recommended) through the barrel connector. Logic level 3.3 V.

⚠ Warning: Installation must be carried out by a qualified electrician. Switching modules and power supplies are not included.