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 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.]

#homehacks #microcontrollers #acrylic #kitchentimer #ledmatrix #ledmatrixdisplay #rotaryencoder #timer

clOCkTAL: For When Reading A Clock Is Just Too Easy

Over on Hackaday.io, [danjovic] presents clOCkTAL, a simple LED clock for those of us who struggle with the very concept of making it easy to read the time. Move aside binary clocks, you're easy , let's talk binary coded octal. Yes, it is a thing. We'll leave it to [danjovic] to describe how to read the time from it:

Do not try to do the math using 6 bits. The trick to read this clock is to read every 3-bit digit in binary and multiply the MSBs by 8 before summing to the LSBs.

Simple. If you're awake enough, that is. Anyway, we're a big fan of the stripped-down raw build method using perf board, and scrap wood. No details hidden here. The circuit is straightforward, being based on a minimal configuration needed to drive the PIC16F688 and a handful of LEDs arranged in a 3×4 matrix.

An interesting detail is the use of Bresenham's Algorithm to derive the one event-per-second needed to keep track of time. And no, this isn't the more famous Bresenham's line algorithm you may be more familiar with, it's much simpler, but does work on the same principle of replacing expensive arithmetic division operations with incremental errors. The original Bresenham's Algorithm was devised for using with X-Y plotters, which had limited resolution, and was intended to allow movements that were in an imperfect ratio to that resolution. It was developed into a method for approximating lines, then extended to cover circles, ellipses and other types of drawables.

Bresenham's Algorithm allows you to create the event you want, with any period from any oscillator frequency, and this is very useful indeed. Now obviously you don't get something for nothing, and the downside is periodic jitter, but at least it is deterministic. The way it works is to alternate the period being counted between two power-of-two division ratios (or something easily created from that) such that the average period is what you want. Cycle-to-cycle there is an error, but overall these errors do not accumulate, and we get the desired average period. The example given in [Roman Black]'s description is to alternate 16 cycles and 24 cycles to get an average of 20 cycles.

The software side of things can be inspected by heading over to the clOCkTAL GitHub which makes use of the Small Device C Compiler which has support for a fair few devices, in case dear readers, you had not yet come across it.

The video shows the clock being put through a simple test demonstrating the LED dimming in response to ambient light. All-in-all a pretty simple and effective build.

#clockhacks #bresenham #ledmatrixdisplay #octal #pic16f #sdcc