Hewlett-Packard used to make some pretty cool LED displays, many of which appeared in their iconic pocket calculators back in the 1970s and 1980s. [Upir] tracked down some of these classic bubble displays and used them with a microcontroller. We love the results!
The displays featured here, the HPDL-1414, aren’t quite what would have been found in an HP-35, of course. These displays have 16 segments for reasonably legible approximations of most of the ASCII character set. Also, these aren’t just the displays; rather, a pair of the bubble-topped displays, each with four characters, is mounted to a module that provides a serial interface. [Upir] found these modules online, but despite the HP logo on the PCB silkscreen, it’s not really clear who made them. The documentation was a bit thin, to say the least, but with a little translation help from Google, he figured out the serial parameters and the character encoding. The video below shows him putting these modules through their paces.
Unusually for [upir], who has made a name for himself hacking displays to do things they weren’t designed to do, he stuck with the stock character set baked into this module. We think it would be fun to get one of these modules and hack the firmware to provide alternative character sets or even get a few of the naked displays and build a custom interface. Sounds like a fun rainy-day project.
This reminded us of another HP display project we saw a while back. Or, roll your own displays.
Amazing, somebody took a commercial part and used it as intended. That is properly mind-blowing !
Not quite as useless as complaining about someone who actually made something all the while not doing something constructive yourself …
THAT hard to get the datasheet: https://www.farnell.com/datasheets/76528.pdf
The bare HPDL-1414 are great for retrocomputing, they are 8-bit parallel and super easy to throw on a bus. A few years ago you could get them for about $0.80 per 4-character module, but now they seem to cost 5x as much. Should have stocked up, but that’s still a better deal than the TIL311’s.
What you don’t want to do is clean them with rubbing alcohol, as it will crack the plastic. Luckily I did not try to clean all of mine at once.
That’s good to know about the alcohol! I have a handful of QDSP 6064 modules in my parts bucket (similar, but only 7 segments per character, and absolutely teeny tiny). The problem is that since I learned they were discontinued, they feel too precious to actually use for anything.
I guess I should try to come up with a project specifically to show off their extreme retro cuteness, as there’s no point leaving them in a baggie for the next 20 years.
Broadcom / Avago still makes and sells tiny, really neat dot-matrix LED displays that go in DIP sockets, in 4, 8, and 16 characters each, with serial input that lets you tell them which dots you want illuminated, so you can make custom characters as well. The synchronous-serial interfaces can be daisychained, so you can make an array of them with a single serial feed. The only drawback I see to them is that they’re super expensive. Let’s see if a link is allowed here. This should bring up Mouser’s listing of all the colors and numbers of characters that are active, normally stocked, and in stock: https://www.mouser.com/c/optoelectronics/displays/led-displays-accessories/?q=Avago&display%20type=5%20x%207%20Dot%20Matrix&number%20of%20digits=4%20Digit~~16%20Digit&instock=y&active=y&normallystocked=y&rp=optoelectronics%2Fdisplays%2Fled-displays-accessories%7C~Number%20of%20Digits
Really nice modules but boy those prices…
Prices are worse than you think. It’s getting to the point they’re worth making again, although a bigger bubble please. HP 5082-7414 $195 for the 4 digits:
https://www.surplussales.com/Bulbs-Incan-Panel/LEDDisplay.html
You don’t need a display with built-in driver IC, too expensive.
I have 16-seg. pulled from kid’s toys that are really sweet but you have to do the mux code.
Hey, i got some HP 5082-7405 bubble displays years a go. And I did a little bit of tinkering with those too
https://youtu.be/UI49Mjx5CSg?si=PxlPX8NvwRBUt8gf
Its so cool that one can still find datasheets for those.
I have a demo board for HPDL-1414s , which also can demonstrate it’s larger brothers, the HPDL-2416 and the HMDL-2416. It only uses three active components: a 2716 EPROM, a 4020 counter and a 74C00 configured as an oscillator. It runs on 4 ‘C’ cell batteries without a voltage regulator. When turned on, it scrolls a message about HP displays, followed by the entire character set. As I recall, there is a mistake in the EPROM which causes one character to be incorrectly displayed.
“Hewlett-Packard used to make some pretty cool […]” could be said of many things. All of which were in the years BC (Before Carly)
One thing to note. These devices have a letter code on the right corner . I believe it’s A-F. This pertains to the brightness of the LED. You’ll want to get units of the same letter code if possible or there will be a noticeable difference in brightness.
Those who work on restoring old HP calculators that use these bubble displays, would really love to find suitable affordable, replacements.
See Hpmuseum.org
These are parallel, not serial. 7 lines but effectively 6 bits, because the ASCII control area and the lowercase block isn’t included.
They can’t be “reprogrammed” because they’re simple digital latches with look-up tables attached.
Judging by the bluish-green PCB color they’re replicas and not vintage parts. I wish more companies made replicas.
I just realized they were talking about a serial module, not the bare displays. My point about the reprogramming stands. Dan probably thought the displays are simple LED matrices like quad 7-segment modules but they’re not. The displays themselves have the 7-bit ASCII drivers inside. I’ve hacked my way around them a lot (before I had a datasheet or even a pin-out) and destroyed quite a few. I was barely a teenager, ok? Aside from fully functioning without a VDD attached (supplying power via the ~CE pin, and the obvious dimming via VCC, there isn’t much to say about them in terms of hackability.
I just realized they were talking about a serial module, not the bare displays. My point about the reprogramming stands. Dan probably thought the displays are simple LED matrices like quad 7-segment modules but they’re not. The displays themselves have the 7-bit ASCII drivers inside. I’ve hacked my way around them a lot (before I had a datasheet or even a pin-out) and destroyed quite a few. I was barely a teenager, ok? Aside from fully functioning without a VDD attached (supplying power via the ~CE pin), and the obvious dimming via VDD, there isn’t much to say about them in terms of hackability.