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Looking for the name of a numerical display that uses dots, a bit like a 7 segment.

Discussion in 'Electronics & Electrics' started by oculi, Jan 27, 2021.

  1. oculi

    oculi Member

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    So in university a piece of lab equipment had an electron number display, each element used dots (VFD or Neon or something) to form the numbers, not an array, was a bit like a 7 segment display but with dots instead of bars and maybe not 7 of them.

    Anyone know what they are called?

    Wasn't a nixie, wasn't a numitron.

    TIA
     
  2. Renza

    Renza Member

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  3. OP
    OP
    oculi

    oculi Member

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  4. rockofclay

    rockofclay Member

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    Could you mspaint the array?
     
  5. OP
    OP
    oculi

    oculi Member

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    No I can't remember what it looked like, that's what I want to know.
     
  6. mtma

    mtma Member

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    Does it look like the displays on the original generation of MicroTAC?
    https://en.wikipedia.org/wiki/Motorola_MicroTAC

    That's a VFD and I think they were mostly red, but there was also a green variant.

    ED- also perhaps you're thinking of a 12 or 14 segment display if it wasn't just a grid. Think back to the future (although on close inspection to the movie captures you'll notice that parts of the display that should have been 12 or 14 segment were faked)
     
    Last edited: Jan 27, 2021
  7. merlin13

    merlin13 Member

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    Pretty specialised nowadays methinks - not being full Dot Matrix means that display would be for cosmetics only, to stand out from the crowd.

    Haven't used or seen one of those for absolute yonks myself, last ones I recall actually touching were Siemens branded (I think), if that helps.

    You might need to troll/scroll though all the offerings from the Usual Suspects who supply digit LED displays.

    Ha - first mobile phone I ever drowned was one of those...
     
  8. Technics

    Technics Member

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    The description is a little hard to go on. I have some like this from avionics. They used incandescent bulbs and light pipes.

    https://www.industrialalchemy.org/articleview.php?item=3086

    There are some projection and edge lit types that somewhat fit your description is well.

    That website is pretty comprehensive when it comes to electronic display history and esoterica so maybe browse around
     
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  9. Technics

    Technics Member

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    Also some of the HP LED displays come to mind too.



    These have built in decoders and drivers. Cool but expensive (because they are needed for old equipment and some odd people collect such things)
     
    Last edited: Jan 27, 2021
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  10. OP
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    oculi

    oculi Member

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    Cheers all! YouTube ended up being the most
    helpful, I think they might have been HP 4N51 displays



    (close in design to the video in the post above)

    Prices for these kinds of things can be rather eye watering, I'm just after the design so I can copy it using individual LEDs or whatever.
     
  11. Technics

    Technics Member

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    You might want to check out the Texas Instruments TIL311 as well but I believe it's a bit smaller. It does already have a modern recreation https://hackaday.io/project/166086-diytil311

    There's also the HP 5082-7340 and the 5082-7359. They aren't mil spec like the 4N51 and will probably be easier to find.
     
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  12. OP
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    oculi

    oculi Member

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    Cheers! I think they were red 5082-7340 displays, I remember the visible circuitry on the front face.
     
  13. breech

    breech Member

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    I recently found a handheld Agilent demo unit buried in a cupboard at work with leaked batteries, I cleaned it up and it came good. Let me know if you need any photos or part numbers, they are similar to HCMS-3966, about 6 types installed with various colours and text sizes.

    This page has a few more types
    http://www.decadecounter.com/vta/tubepage.php?item=33
     
    Last edited: Mar 14, 2021
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  14. Supplanter

    Supplanter Member

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  15. Technics

    Technics Member

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    The many different versions of these are all evolutions of the original HP HDSP-2000 (http://hparchive.com/PARTS/HP-Displays-HDSP-2010.pdf). Later products integrated the display RAM and column drivers and accepted parallel or serial data directly. I have a load of the 8 character SPI and parallel versions and some of the 4 character SPI versions of these. They weren't cheap retail but they occasionally show up in surplus lots on eBay. When you create large strings they start to require some serious current (and along with it the need to carefully consider the thermal design). In addition to HP (AKA Agilent, AKA Avago, AKA Broadcom), Osram and Siemens also produced variations of these types of LED matrix display modules over the years. There were also versions that used 16 segments instead of the 5x7 matrix.
     
    Last edited: Mar 16, 2021
  16. OP
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    oculi

    oculi Member

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    definitely wasn't full bitmap

    cheers, i'm not looking for them, just the design and what each character looks like. Kinda off track but I wonder if any displays are designed (at a hardware or control level) to give off uniform brightness? for example the number 8 will give a light level ~3.5 times brighter than the number 1, so to be less disruptive you would limit power to the 8 overall. it would look funny if you were trying to read the numbers though.
     
  17. mtma

    mtma Member

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    I wonder if those displays that seemed to have power source problems where high filled characters dimmed were actually doing this. But I think it might just be by accident than intended design. For example if you had a time division multiplexing setup then scanning over lesser segments could result in higher brightness as you can alot greater duty to each segment. (Although, constant scan rate is a more common setup)

    I'd imagine if you were balancing appearance and power budget you would dim the entire text area to meet the overall power budget. Perceived intensity isn't linear so a small variation in current across the whole display would be an even smaller perceived intensity variation.

    ED-
    I'd guess there must be some kind of aviation use for a constant-lux display implementation
     
    Last edited: Mar 17, 2021
  18. Technics

    Technics Member

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    I haven't seen anything like that done for displays with integrated electronics. Although I have seen attempts to reduce component count with seven segment LED displays by using one current limiting resistor in the common anode/cathode of instead of a resistor for each segment which would lead to a similar effect.

    On the subject of brightness. Many LED displays came with an extra code after the part number to indicate the binning for brightness ranges so that it could be matched across multiple displays. One interesting application note for the HDSP/HCMS series alphanumeric displays covered the synchronization of the blanking input signal with the internal clock in order to achieve dimming to much lower levels than the internal controller normally allowed. This was so that they could be used in instruments that would be observed by pilots wearing night vision goggles. Mil spec versions of these displays in ceramic packages are relatively common.
     

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