Minimalist Timer Counts Down With LED Matrix

Looking for something with a bit more style than the traditional kitchen timer, [Martin Jonasson] decided to take the last couple of months to design and build his own take on the idea using a rotary encoder, 16×9 LED matrix, and a Teensy 2.0 microcontroller. Were there better things he could have spent that time on? Possibly. But you probably wouldn’t have been reading it about it here, so we won’t trouble ourselves with such thoughts.

Put together on a piece of perfboard, the handwired circuit also includes an Adafruit PowerBoost 500 Charger, a 3.7 V 2500 mAh LiPo battery, a IS31FL3731 Charlieplexed PWM LED driver, and a piezo buzzer. The top of the rotary encoder has been capped off with a sold metal knob, which combined with the enclosure made of stacked laser cut 3 mm acrylic sheets, really gives the device a very sleek and classy look.

While the hardware is quite nice, it’s the software that really pulls this whole project together. A game developer by trade, [Martin] went all in on the timer’s GPLv3 licensed firmware. From using the toneAC library to play melodies at the end of the countdown, to the custom fonts and the code that pauses the timer while the user is spinning the knob, there’s plenty of little touches that should make the timer a joy to use. We’ve seen some unique kitchen timers over the years, but the attention to detail put into this build really raises the bar.

[Martin] has provided everything you need to create your own version of his timer, including the SVG file for the laser cut case. While not strictly required, coming up with a custom PCB for this project would be a nice touch, should you want to put your own spin on it.

[Thanks to Tom for the tip.]

3 thoughts on “Minimalist Timer Counts Down With LED Matrix

  1. This is excellent! I like the rotary encoder to set the interval rather than pressing and holding buttons. Rarely do you see a knob to set the timer. ( I remember James Bond had that on a bomb timer – not that this should be used for that ! – got to remember not to type out my inside voice đŸ˜„ ) . I have seen a lot of digital timers and I have a couple of question…. what are you using for a time base ? How sure are that one second is one second. ? How sure there won’t be some drift ?

    1. I use the Teensy’s elapsedMillis call to work out the time, it’s accurate enough that I can’t discern any drift over 30 minutes as compared to my phone and casio wristwatch. That’s perfectly good enough for my purposes.

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