This is based on Arduino. Four displays show the time. At the time a modified relay strikes a fire extinguisher which provides a bell-like sound. It has to be a CO2 type : powder or liquid types do not work.

It looks a bit Al-Qaedian, so be careful as to where you display it.

Also, fire extinguishers are under pressure so be careful not to hit them too hard.

The circuit board:

This is the clapper made with a modified relay :

This is the schematic : the circuit is intended to be connected to an Arduino board. The name on connectors are Arduino’s.

This is the sketch to be downloaded into the microprocessor: Fire extinguisher striking clock

And this is a video of the clock in action :