13 ms·

To be fair, it's not always either-or: an OLED display of 128x32 or 128x64 resolution costs peanuts and requires 4 lines for routing (I2C), and I've used them o

by ivoras 6y ago

To be fair, it's not always either-or: an OLED display of 128x32 or 128x64 resolution costs peanuts and requires 4 lines for routing (I2C), and I've used them on 8bit uCs. Like https://s.click.aliexpress.com/e/_9flw1u https://s.click.aliexpress.com/e/_9flw1u And there are higher resolution and higher color fidelity displays which are also cheap and driven by I2C.

bsder 6y ago
$1.30 isn't peanuts. 1 penny is peanuts: https://www.alibaba.com/product-detail/6-digit-8-characters-pen-Segment_60347971499.html?spm=a2700.galleryofferlist.normal_offer.d_title.757211f6FVMZKy https://www.alibaba.com/product-detail/6-digit-8-characters-... https://www.alibaba.com/product-detail/TN-segment-custom-LCD-display-pen_60347119657.html?spm=a2700.details.0.0.5dd53f53hbCjRp https://www.alibaba.com/product-detail/TN-segment-custom-LCD... People use seven segment LCDs because they're cheap. No more, no less.
- yholio 6y ago
  I think the author's argument stands: except for novelty products, there are very few applications where the misinterpretation risk is worth less than $1. Certainly nothing that has to do with safety, medical equipment, professional and industrial tooling, food processing, automotive (pressures, temperatures etc.). An one segment error leading to a 30 PSI reading when the pump is set at 90 could mean instant death when the tire blows up.
  - bsder 6y ago
    > there are very few applications where the misinterpretation risk is worth less than $1 Any product required to run on a battery 5+ years can only be met by seven segment LCDs. That's includes safety equipment. Now what? In addition, that seven segment display has well characterized failure modes and you can make very solid statistical predictions. When was the last time you actually remember a burnt out LCD segment (I can't remember one) vs. the last time you had nasty lines running through a dot matrix LCD (happens to flat panels all the time)? On a matrix, display RAM failure is a display failure. Seven segment LCDs don't need RAM backing. Are you willing to have your medical device offline because you lost an LCD matrix row and now you are required by process to wait for a replacement? How much time and money did that cost you? These are the exceptions. LCDs are normally about cheap. And if the device isn't cheap enough, you won't have that safety/medical device at all because nobody will buy it. Engineering is tradeoffs, not absolutes.
    - yholio 6y ago
      The main takeaway here is exactly this huge risk of gradual deterioration leading to invalid output that appears valid. That a thermometer fails in the hospital or runs out of battery is not a major problem - another one is close by and procedures are in place to deal with it. Meanwhile, a wrong temperature read can lead to life critical decisions by the medical staff (ex. 39 vs 33). While I agree with your engineering tradeoffs perspective, failing safe is also a major recurring theme in engineering. When errors or loss of functionality happen they should be obvious and stop the system (machine + human operators) from spiraling out of control. A compiler won't silently write integers to a byte* pointer, because that might kill your patient where the parameter goes over 255. A failed display is preferable to a working display that outputs wrong data. By the way, 14 and 16 segment displays are widely available in passive LCD formats and draw the same power, while the upgrade to dot matrix LCD is not that prohibitive, I had it on my MP3 player 15 years ago.
      - bsder 6y ago
        People make far more errors like not checking at all--and you can't even get them to use checklists which are close to free. LCD segment failure causing a misinterpretation is so far down the list of things to go wrong that it might as well be zero. 14/16 segment displays require more microcontroller pins (twice as many, in fact). That goes back to cost. Your MP3 has a very expensive, high-capacity rechargeable battery which will not hold a charge 5 years even if you connect it to nothing.
- deleted 6y ago
  [deleted]
- kabdib 6y ago
  On really high volume consumer electronics, multiply any cost savings by tens of millions. Now you're talking real money. The HW engineers have knife fights in the hallways over resistors that cost less than a penny. I'm kidding about the knives. But cost reduction meetings can be pretty brutal, especially when the HW team is looking at the SW and firmware folks across the table and saying, "Sure, this is painful, but you can program around it. It saves us ten cents." Ten cents is a fortune. In pre-ARM days I once saw a HW team seriously propose half populating memory. No, not that way. The other direction, where they'd just take away the upper half of each byte of RAM and thus save a chip. "Only use the low four bits of each byte, you can just program around that, right?" The only reason that cost reduction didn't fly was there was no way to make the stack work properly for interrupts. First rule of consumer electronics: "No one cares how much you suffered getting it out the door."
- ivoras 6y ago
  Yeah, $1.30 isn't peanuts... but that price is for low volumes (single modules) on a retail site. High volume production probably slashes that down to about half, and then we're in the price range of 7 segment LCD panels like linked above, especially when counting in a controller (and we'll likely need a controller if driving it from an 8 bit uC). Of course, when absolute $ savings are more important than resolution / legibility, tens of cents are worth looking into. Power requirements are another topic, and monochrome LCDs are unmatched there.
magicalhippo 6y ago
Fonts for that can still take up a considerable amount of storage. And 7-segmented displays can typically update faster, especially the LED variants. That said, I mostly agree that a small OLED or similar is usually a lot better to read.

by ivoras 6y ago

bsder 6y ago

$1.30 isn't peanuts. 1 penny is peanuts: https://www.alibaba.com/product-detail/6-digit-8-characters-pen-Segment_60347971499.html?spm=a2700.galleryofferlist.normal_offer.d_title.757211f6FVMZKy https://www.alibaba.com/product-detail/6-digit-8-characters-... https://www.alibaba.com/product-detail/TN-segment-custom-LCD-display-pen_60347119657.html?spm=a2700.details.0.0.5dd53f53hbCjRp https://www.alibaba.com/product-detail/TN-segment-custom-LCD... People use seven segment LCDs because they're cheap. No more, no less.

yholio 6y ago
I think the author's argument stands: except for novelty products, there are very few applications where the misinterpretation risk is worth less than $1. Certainly nothing that has to do with safety, medical equipment, professional and industrial tooling, food processing, automotive (pressures, temperatures etc.). An one segment error leading to a 30 PSI reading when the pump is set at 90 could mean instant death when the tire blows up.
- bsder 6y ago
  > there are very few applications where the misinterpretation risk is worth less than $1 Any product required to run on a battery 5+ years can only be met by seven segment LCDs. That's includes safety equipment. Now what? In addition, that seven segment display has well characterized failure modes and you can make very solid statistical predictions. When was the last time you actually remember a burnt out LCD segment (I can't remember one) vs. the last time you had nasty lines running through a dot matrix LCD (happens to flat panels all the time)? On a matrix, display RAM failure is a display failure. Seven segment LCDs don't need RAM backing. Are you willing to have your medical device offline because you lost an LCD matrix row and now you are required by process to wait for a replacement? How much time and money did that cost you? These are the exceptions. LCDs are normally about cheap. And if the device isn't cheap enough, you won't have that safety/medical device at all because nobody will buy it. Engineering is tradeoffs, not absolutes.
  - yholio 6y ago
    The main takeaway here is exactly this huge risk of gradual deterioration leading to invalid output that appears valid. That a thermometer fails in the hospital or runs out of battery is not a major problem - another one is close by and procedures are in place to deal with it. Meanwhile, a wrong temperature read can lead to life critical decisions by the medical staff (ex. 39 vs 33). While I agree with your engineering tradeoffs perspective, failing safe is also a major recurring theme in engineering. When errors or loss of functionality happen they should be obvious and stop the system (machine + human operators) from spiraling out of control. A compiler won't silently write integers to a byte* pointer, because that might kill your patient where the parameter goes over 255. A failed display is preferable to a working display that outputs wrong data. By the way, 14 and 16 segment displays are widely available in passive LCD formats and draw the same power, while the upgrade to dot matrix LCD is not that prohibitive, I had it on my MP3 player 15 years ago.
    - bsder 6y ago
      People make far more errors like not checking at all--and you can't even get them to use checklists which are close to free. LCD segment failure causing a misinterpretation is so far down the list of things to go wrong that it might as well be zero. 14/16 segment displays require more microcontroller pins (twice as many, in fact). That goes back to cost. Your MP3 has a very expensive, high-capacity rechargeable battery which will not hold a charge 5 years even if you connect it to nothing.
deleted 6y ago
[deleted]
kabdib 6y ago
On really high volume consumer electronics, multiply any cost savings by tens of millions. Now you're talking real money. The HW engineers have knife fights in the hallways over resistors that cost less than a penny. I'm kidding about the knives. But cost reduction meetings can be pretty brutal, especially when the HW team is looking at the SW and firmware folks across the table and saying, "Sure, this is painful, but you can program around it. It saves us ten cents." Ten cents is a fortune. In pre-ARM days I once saw a HW team seriously propose half populating memory. No, not that way. The other direction, where they'd just take away the upper half of each byte of RAM and thus save a chip. "Only use the low four bits of each byte, you can just program around that, right?" The only reason that cost reduction didn't fly was there was no way to make the stack work properly for interrupts. First rule of consumer electronics: "No one cares how much you suffered getting it out the door."
ivoras 6y ago
Yeah, $1.30 isn't peanuts... but that price is for low volumes (single modules) on a retail site. High volume production probably slashes that down to about half, and then we're in the price range of 7 segment LCD panels like linked above, especially when counting in a controller (and we'll likely need a controller if driving it from an 8 bit uC). Of course, when absolute $ savings are more important than resolution / legibility, tens of cents are worth looking into. Power requirements are another topic, and monochrome LCDs are unmatched there.

magicalhippo 6y ago

Fonts for that can still take up a considerable amount of storage. And 7-segmented displays can typically update faster, especially the LED variants. That said, I mostly agree that a small OLED or similar is usually a lot better to read.