I am a fan of the StrongLifts 5x5 strength training routine. There is indeed an app for Android and iOS, however I found using the app inconvenient for a few reasons:

• After a heavy lifting session, my hands shake too much for me to comfortably use the app
• I keep having to unlock my screen to access the app
• It interrupts the music I play from my phone and necessitates unnecessary app switching
• I find the notifications on the phone distracting me from my gym routine

So I decided to built a simple one-button device to time my rest periods and count my sets for me.

This project took me less than a few hours to build and polish. Initially I built it onto a breadboard, and then tested it for a month. Thereafter, I built it into a shield using the prototyping shield.

The Gym Timer works so well that even my wife enjoys using the device! The source code and circuit diagram are available in the GitHub repository, in case you want to build your own.