This is a fun electronics hobby project I've been working on since August 2019.
It is a timer (actually a stopwatch) for meetings that calculates the costs, based on the hourly rate of the participants.
It was inspired by the long, often dreary, meetings me and my teammates would sometimes have to endure.
I envisioned a better world where people would be aware of the costs of long meetings, hoping that would make them get to
the point more quickly :D

It is based on an Arduino Nano, with a shift register to control the LED and a rotary encoder for input.
As the Arduino Nano comes equipped with its own internal voltage regulator, this device runs nicely on a 9V block battery,
even while the circuit and the microcontroller require only 5V.

There are some small indicator LEDs to show when the power is on and when the clock is running.
The rotary encoder used to set the average hourly rate and the number of participants, is a standard KY-040.
I use a library to decode the turns of the KY-040, which is needs on 2 interrupts on the Arduino Nano.
The code for this library can be found on:
https://github.com/oudesnepelaar/Rotary-Arduino-library

There is a video on YouTube thats shows a quick demo of the controls.
'R' sets the rate in euros per hours, 'P' sets the number of participants to the meeting.
The clock then updates the total cost every second while it's running, showing euros (or any other currency depending on the rate setting). More or less like a taxi meter, but for meetings with multiple participants.

The schematic was designed using EasyEDA.

This repo contains:

 - Arduino sketch (INO) for the program - tested successfully on Arduino Uno & Nano
 - EasyEDA source file (JSON) for the schematic - in case you want to change it a bit for your own use
 - PDF file of the component schematic - for easy viewing

The /pics folder shows some snaps of the building of the device in different stages.
Also, check out the Imgur gallery:
https://imgur.com/gallery/hHFEcQb
 
The video briefly showing the device in action, can be found on YouTube:
https://youtu.be/manwS1O5PpQ
 
Ferrie J Bank,
Amsterdam, 27 May 2020

https://github.com/oudesnepelaar