Mini LED message board built from retro displays

personal_electronic_retro_telegram

[Iain] is getting to the point in his life where he finds himself waxing nostalgic about various different technologies from his youth. One item he has always been fond of is first generation 7 segment consumer LED displays, like those found in old calculators.

He was excited to find one of these displays at the bottom of a box full of electronics odds and ends he received from a friend. After identifying the display and tracking down a data sheet online, he decided that he wanted to build some sort of little gadget out of it.

His first inclination was to build a tiny text scrolling gadget from the display, and thus his “Personal Electronic Retro Telegram” (P.E.R.T) was born. With Arduino in hand, he prototyped the circuit on a breadboard, then sent away to have some PCBs built. Once he received the boards, alll of his prototyping components were swapped out with SMD versions, including a TQFP ATMega168 chip in place of the full-sized Arduino board.

The final result is a nice melding old and new technology which he decided to give to his girlfriend as a gift. Continue reading to see a quick video of the P.E.R.T in action.

19 thoughts on “Mini LED message board built from retro displays

  1. I love these micro 7-segments! I’ve been parsing eBay for those for years and have a few of them now. Would be nice if the author made just the board available. He eluded to difficulty in sourcing parts (I think he meant only the display) but for someone like me that actually has the display, I would love to have the board (and, frankly, an application – they are not so cute just laying around) for it.

  2. OK, so they aren’t quite as small as a single unit above but you can buy individual 9mm high 7 segs from conrad.com. They do a 4 digit version as well. 14mm digit height though.
    I’m sure some clever hackadayers ought to be capable of making these mini 7segs out of a pile of LEDs. Maybe put an SMD LED on the board and have a mask above…

  3. 9mm? dude, that’s huge compared to the ones he used. The tiny size is what makes them so cute. I think the digits are something like 4mm high or even less (before the epoxy lens)

  4. I made one of these back around 10 years ago, as one of my very first electronics projects that used a microcontroller. Here is a link to some pictures.

    http://www.decadecounter.com/vta/articleview.php?item=1055

    The controller is a boring old PIC 16F84, which was what all the cool kids were using back then. Here is a page that contains lots of photos and information on these old types of LED displays.

    http://www.decadecounter.com/vta/tubepage.php?item=33&user=0

    You can still find many displays of this type on Ebay for $10 – $25 dollars each.

  5. Bit of a limited project. No matter how “cute” the display is, I predict this is already sitting in the back of Claire’s knicker drawer.

  6. I have a bunch of these displays i pulled out of some old pagers (pre-LCD models) – they are beautiful, and someday i’ll get the time to do something with them…

  7. I was just thinking yesterday that people hadn’t been using these for anything. Seeing how nixie tubes have gotten so popular, you’d think these would have gained some popularity too.

  8. Judging by how the discussion is shaping up they may get popular again one day! :)

    In any case, I can’t believe no one has an application for a tiny numerical indicator that can be driven directly by an MCU (5mA per segment and the old catalog claims “Excellent Readability at only 250uA per segment”) . Three digits in only a 15.37mm x 7.62mm package? I can’t believe they don’t make them anymore, they seem like a must have item!

    Oh, and I stand corrected: the digits are only 3mm tall (before they get blown up by those lens)

  9. I have a mini frequency meter I made using two of these using a PIC 16F84 and assorted logic..

    Works fine, shame it has the last digit missing but I just have to mentally add 10 to the result.

  10. I LOVE this type of display! It’s such a shame that these aren’t made anymore. But some more similar types ( such as HPDL-1414 ) are still made IIRC.

  11. @Mattster: They are about the same size, a bit larger and many more leads due to individual digits wired. But they lack the drama of the over-sized lens! I think I saw it on
    http://www.decadecounter.com where they call these lens forms suggestive :) . Well, my 3-digit/3-lens displays can sure be suggestive to someone who’s old enough to remember Total Recall … :)

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