A few years ago, I was training at a mixed martial arts gym. (I've tried all sorts of crazy things in my life, and this one was incredibly fun!) During training, we frequently followed a routine of fighting for 3 minutes followed by a 1-minute rest period. The problem was that the gym didn't have a proper interval timer, so we were using a kitchen timer instead, which was terribly inconvenient.

To solve this problem, I built a custom timer using a dot matrix LED display and an Arduino Nano, which I then donated to the gym.

How It Works

The timer functions as follows:

• When powered on, it displays the round number and begins a 3-minute countdown
• Short beep sounds at 2 minutes, 1 minute, and 30 seconds remaining
• During the final 10 seconds, increasingly higher-pitched beeps count down "Ten! Nine! Eight!" and so on
• After "One!" it announces "DRINK!" with a long beep sound, starting the 1-minute rest period
• The Round 2 start is preceded by a 3-second countdown
• Then "Round 2 FIGHT!" signals the beginning of another 3-minute round
• The rounds continue to increase infinitely (though the display gets a bit messy when the round number reaches double digits! 😂)

Although it doesn't have actual speech capability, I think the cheap BEEP sounds for counting and the buzzer worked out better than expected.