Word clocks, or a matrix of light-up letters that spell out the time, are a standard build for all enterprising electronics enthusiasts. The trouble is finding the right way to drive a matrix of LEDs and the significant amount of brainpower that goes into creating a matrix of letters that will spell out the time without making it look like it’s supposed to spell out the time.
For his Hackaday Prize entry this year, [Stephen Legge] is creating a standard toolkit that makes word clocks easier to build. It’s a hardware and software project, allowing for LED matrices of any reasonable size, and the software to make a grid of letters that only spells out the words you want and not the four-letter ones you don’t.
The hardware for this project is built around the IS31FL3733 LED driver from ISSI. This is an interesting chip that takes I2C in and spits out a LED matrix with very few additional support components. This chip provides [Stephen] with a 12×16 single-color LED matrix, which is more than enough for a word clock.
Where this build gets slightly more interesting is the creation of a custom matrix of letters that will still spell out ‘quarter to noon’ when lit in the appropriate way. This is a big challenge in creating a customized word clock; you could always borrow the layout of the letters from another word clock, but if you want customized phrases, you’ll either have to sit down with a pencil and graph paper, or write some software to do it automatically.
It’s a great project, and since all of [Stephen]’s work is being released under Open Source licenses, it’s a great entry to the first portion of the Hackaday Prize where we’re challenging hardware creators to build Open Hardware.
It seems that most of the electrical engineering covered on Hackaday concerns exactly one problem domain: how to blink a bunch of LEDs furiously. There are plenty of LED drivers out there, but one of the more interesting in recent memory came from ISSI in the form of a chip that turns I2C into a Charlieplexed LED array. You may have seen this chip — the IS31FL3731 — in the form of an Adafruit LED matrix and some stupid thing some idiot made, but with it you’re only ever going to get 144 LEDs in an array, not enough if you want real blinky bling.
Now ISSI has released a more capable chip that turns I2C into many more
Charlieplexed LEDs. The IS31FL3741 will drive up to 351 LEDs in a 39×9 matrix, or if you’re really clever, an 18×18 single color LED matrix.
Features of this chip include reverse/short detection for each individual LED, 8-bit PWM, dimming functions, a de-ghosting feature that guarantees a LED is either on or off, a configurable row/column matrix, and a few other handy tools that you would like to see in a LED matrix driver chip. The most impressive chip in this series will be available for under $2/piece in quantities of 2500, although unlike the IS31FL3731, it appears this new chip will only be available in a QFN package.
Speaking from experience, this is a really great chip for driving a whole boatload of LEDs, provided you have a pick and place machine. Yes, you can hand-solder a QFN and several hundred 0402 LEDs, but I wouldn’t recommend it. I really, really wouldn’t recommend it. That said, this is the perfect chip for maximum blinky bling, and the press material from ISSI gives us the great idea of using one of these chips as the backlight controller for RGB LED mechanical keyboards. That’s a great application, and the chip is pretty cheap, too.
You can check out ISSI’s blinky demo video of this chip below.
Continue reading “New Part Day: I2C In, Charlieplexed LEDs Out”