There was once a golden age, somewhere between when we first saw LEDs pop into existence, and before they advent of high-density layouts, giving us infinitely reconfigurable screens.
Somewhere in the middle of these two time periods, we were treated to a golden age of glorious looking LED displays, ranging from the simple seven-segment numeric displays, to more advanced alpha-numeric arrays, capable of cramming numerals and text into far tinier spaces than the Nixie tubes of the days prior would ever allow.
These displays, like the Nixie tubes they replaced, often carry a special, nostalgic admiration form anyone who has been lucky enough to see the lovely luminous glow that they are known for.
With the hefty voltages and complex driving arrangements needed to manage the tube heaters and bias potentials, the warm glow of a Nixie tube is beautiful to behold, but can pack a real bite when it comes to building a circuit that is going to be able to drive them correctly — some Nixies can require up in the region of ~100V to drive the filaments inside. Yikes!
So, given that these tiny little LED displays offered so many advantages over the long-in-the-tooth Nixie tubes of yesteryear, it's no wonder they were so popular at the time.
With not only lower, but simpler power requirements, smaller overall size, and a whole variety of arrays an form factor specific variants made possible by the same technologies used to manufacture ICs — these LED displays were lavishly deployed literally everywhere. From computers to calculators, even watches were all popular use cases for these little LED displays — and we all know how much we love a good watch over here at Hackster!
One particularly popular range of these LED-based parts were the TIL311 range of single-character display modules.
These dinky, DIP-packaged, resin-cast parts packed in the necessary number of LEDs required to make up the alphanumeric character display, along with a binary coded interface that abstracts the addressing of the multiple LEDs down to a simple set of 16 possible states, set over four pins, seen below as the Data Input [A-C] pins.
By setting the state of the four inputs to any of the possible 16 states, the internal decoder will illuminate the appropriate LEDs as required, in order to allow the user to select any of the hexadecimal characters, shown below.
However. as we all know, technology moves fast. We're sat a long, long way from these LED displays, all the way over here with our super flexible HD AMOLED panels that can be rolled around a pencil....
The TIL311, are for all real purposes, EOL. This, while understandable, has left a bit of a gap in the market for those looking to serve the desires of designers who are looking to drop a bit of that retro geek chic on to their PCBs.
There are no shortage of designs that look to make use of these EOL LEDs — be they the TIL311, or other slightly more advanced versions, used by the popular Pixie.
That shortage means that there's a bit of a shortage on the existing stock — what's an aspiring designer to do in lieu of these parts?
If there's one person we know who's got the penchant for packing pixels into tiny PCBs, it's @tinyledmatrix. We've seen his work before with previous DIP-format, dinky LED displays of all varieties. There's the PICTIL, seen below...
Or there was even the complimentary CoPixie, a fusion of the two projects previously mentioned here, with @tinyledmatrix directly placing the otherwise packaged LEDs of the display modules directly on the Pixie board itself.
The results look absolutely gorgeous — you can't argue the allure of this aesthetic.
With the previous PICTIL to build upon, @tinyledmatrix revisitied the design, and returned with a revamped revision — the reTIL.
Having poked and prodded some parts around in the PCB layout, they have ended up with a strikingly similar looking homage to the true TIL311.
Packing the tiny array of individual single LED pixels into place, along with a super-smol STM8S QFN MCU, all on the front face of the PCB, leaves a layout that is almost indistinguishable from the TIL311 when illuminated.
But, @tinyledmatrix didn't stop there, oh no.
Striving for a true-to-form-factor facsimile, the re-vamped PICTIL is placed into a mold, before being cast in the same tinted resin — and the results are just stunning.
Below, we can see the fruits of the labour, with the new, modern take shown on the left, and the original TIL311 to the right
At a casual glance, the difference between these two parts, would probably go unnoticed!
Installed in a product, you'd be hard pushed to tell the difference once the LEDs are lit up!
As we've seen previously in the images, it's clear that being able to specify things on the BoM level of your LED display leaves you open to a litany of options.
First and foremost, LED colours are limited only by what you can get your hands on!
But more than that, let's not forget the fact that there's a ST Microelectronics STM8 in place of the previous binary decoder logic that was once found on the original TIL311
Below, we can see a basic test programme counting through a series of patterns, with only power supplied to the part — so this is clearly something that is going to pe pretty fun to play with!
This opens up the interesting possibilities of programmable, "power-on" patterns, or other such persistent features — it is a programmable MCU after all, it'll be interesting to see the where options are opened up by the firmware as the project progresses!