7 ms·

This is ever so slightly thread-hijacking but I've been wondering something slightly related for a while now: what's the downright cheapest way to get into real

by i336_ 10y ago

This is ever so slightly thread-hijacking but I've been wondering something slightly related for a while now: what's the downright cheapest way to get into really really big LED matrixes? Like the kind used for signs (of various sizes; let's say I'm referring to around <2ft sq). The major issue I'm completely ignorant of is how to get enough I/O that can drive the LEDs directly - I'm assuming something with lots of direct drive I/O and no intermediary components would be the cheapest way to do it (?). I understand multiplexing is the only way to survive at scale, but for small displays (say, 5x30 (= 150 LEDs)), what solutions would have enough I/O to drive each LED emitter individually, without scanning? I've always wondered what a truly flickerless LED matrix would look like. * (* Several years ago I had an odd incident where after using a scientific calculator I'd see weird swirling patterns overlaid on top of whatever I was looking at. The LCD itself was not faulty or damaged, and I couldn't see any flickering at all. Considering LCDs run at 30-100Hz, the whole incident (it stopped after a while, I have some theories as to why) made me curious what a truly DC-driven LED matrix would look like.)

bombela 10y ago
Some LEDs have an integrated chip, making it easy to daisy chain them as a big shift register. Example: https://www.adafruit.com/product/2343 https://www.adafruit.com/product/2343 You can find many similar type of LED in strips, trough holes etc. Some are faster than others. Addressable strips can be used to make big displays it seems: http://hackaday.com/2013/02/25/building-huge-displays-with-led-strips/ http://hackaday.com/2013/02/25/building-huge-displays-with-l...
ChuckMcM 10y ago
As it turns out this is getting pretty easy. A de-facto standard has emerged for these[1] LED modules, both in interfacing and in mounting. I used a couple in a LED clock[2] which can also tell time in QR Code[3] :-). Basically at $25 each you're looking at $3,750 in modules for a 640 x 480 display that in the "P3" (3mm dot pitch) size would be 1.92M wide (75.6") by 1.44M tall (56.7"). All of the LED driving is taken care of by the module, except for multiplexing the 'lines'. So these work by having drivers for one 'line' or LEDs (or 2 lines on the 32 LED high modules). You shift out the bits to them on a 16 pin plug. My clock as using an STM32F4 chip on a 1Bitsy[4] and was doing 240 FPS. Since these micros can be easily paralleled and synchronized you can drive an arbitrarily large sign by adding about $25 per 16 panels. Feeding them all data is a bit more complicated but not terribly so. [1] https://www.aliexpress.com/item/3mm-Indoor-SMD0606-rgb-led-display-module-192mm-x-96mm-64-32-pixle-Video-images-picture/1641364020.html?ws_ab_test=searchweb0_0,searchweb201602_3_10065_10000073_10068_10501_10000077_10000074_10503_10000032_119_10000030_10000026_10000023_431_10000069_10000068_10060_10062_10056_10055_10000062_10054_10000063_10059_10099_10000020_10000013_10103_10102_10000016_10096_10000056_10000059_10052_10053_10107_10050_10051_10106_10000097_10000094_10000091_10000007_10000050_10084_10000101_10083_10000100_10080_10000047_10000104_10082_10081_10110_10111_10112_10113_10114_10000089_10000086_10000083_10000041_10000044_10000080_10078_10079_10000038_10073_10000035_10070_10122_10123_10121_10126_10124-10503_10501,searchweb201603_2,afswitch_3,ppcSwitch_1,single_sort_1_default&btsid=0207e271-5f2c-489f-be15-a3aced211e7a&algo_expid=0eab590f-806a-4601-9f5c-1656aa91ca24-0&algo_pvid=0eab590f-806a-4601-9f5c-1656aa91ca24 https://www.aliexpress.com/item/3mm-Indoor-SMD0606-rgb-led-d... [2] https://twitter.com/ChuckMcManis/status/794023527720620032 https://twitter.com/ChuckMcManis/status/794023527720620032 [3] https://twitter.com/ChuckMcManis/status/794025248203022336 https://twitter.com/ChuckMcManis/status/794025248203022336 [4] https://1bitsquared.com/collections/embedded-hardware/products/1bitsy https://1bitsquared.com/collections/embedded-hardware/produc...
- i336_ 10y ago
  _Wow_, that is truly impressive. $3.7k for a ~2x1.5m² RGB (!!) display - and no added costs (besides a like <$50 interface controller setup). Nice! Hmm. I wonder what the weatherproofing (particularly heatproofing) on these things is like. I know of a time/temp display high up on a building (probably around 1x1.2m²) that is constantly corrupted, I'm wondering if it's the 40°C days around here (Sydney Australia) that keep hitting it... It's fascinating watching how QR encoding shifts and changes data - some of the time updates just adjust a few pixels, some of them adjust the whole barcode. I wonder what the source data for each frame was (but not terribly so). So... if I understand right, these are line-buffered? You send it a line's worth of data, hit "go", and it redraws that line? 240FPS is good, wow. One question: in the first couple of "ticks" of the second hand on the first clock video, I noticed how there appears to be a minor bit of "LED bleed" where some of the LEDs don't switch off for a couple fractions of a second. Curious, I had a look at the video frames: http://imgur.com/a/EVYB2 http://imgur.com/a/EVYB2. Is this an intrinsic problem in the driver system or perhaps a camera or encoding/compression glitch?
  - hantusk 10y ago
    You can get an 80 inch TV for the same cost and roughly the same dimensions. I am curious to understand what this can offer that a TV can't
    - mschuster91 10y ago
      1) a LED "wall" is far brighter than a comparably sized TV, that's important when you place stuff high on a building 2) An ordinary TV is designed to be looked at from the front, a slight angle skews the colors and if it's extreme enough the screen gets totally unreadable. 3) A TV eats up tons of power, a LED wall not so much.
      - wnesensohn 10y ago
        Regarding point 3: At 150 modules consuming about 25W each, your LED wall is consuming about 3750W max. An 80" TV will consume about 300W. Power consumption of the LED wall will, however, be highly dependent on the displayed content. A white screen will consume most, a black screen basically nothing, but displaying only dark images is not exactly what LED walls are usually used for. The equation is simple: The brighter, the more power you'll need, and an LED wall is, as you say, far brighter.

by i336_ 10y ago

bombela 10y ago

Some LEDs have an integrated chip, making it easy to daisy chain them as a big shift register. Example: https://www.adafruit.com/product/2343 https://www.adafruit.com/product/2343 You can find many similar type of LED in strips, trough holes etc. Some are faster than others. Addressable strips can be used to make big displays it seems: http://hackaday.com/2013/02/25/building-huge-displays-with-led-strips/ http://hackaday.com/2013/02/25/building-huge-displays-with-l...

ChuckMcM 10y ago

As it turns out this is getting pretty easy. A de-facto standard has emerged for these[1] LED modules, both in interfacing and in mounting. I used a couple in a LED clock[2] which can also tell time in QR Code[3] :-). Basically at $25 each you're looking at $3,750 in modules for a 640 x 480 display that in the "P3" (3mm dot pitch) size would be 1.92M wide (75.6") by 1.44M tall (56.7"). All of the LED driving is taken care of by the module, except for multiplexing the 'lines'. So these work by having drivers for one 'line' or LEDs (or 2 lines on the 32 LED high modules). You shift out the bits to them on a 16 pin plug. My clock as using an STM32F4 chip on a 1Bitsy[4] and was doing 240 FPS. Since these micros can be easily paralleled and synchronized you can drive an arbitrarily large sign by adding about $25 per 16 panels. Feeding them all data is a bit more complicated but not terribly so. [1] https://www.aliexpress.com/item/3mm-Indoor-SMD0606-rgb-led-display-module-192mm-x-96mm-64-32-pixle-Video-images-picture/1641364020.html?ws_ab_test=searchweb0_0,searchweb201602_3_10065_10000073_10068_10501_10000077_10000074_10503_10000032_119_10000030_10000026_10000023_431_10000069_10000068_10060_10062_10056_10055_10000062_10054_10000063_10059_10099_10000020_10000013_10103_10102_10000016_10096_10000056_10000059_10052_10053_10107_10050_10051_10106_10000097_10000094_10000091_10000007_10000050_10084_10000101_10083_10000100_10080_10000047_10000104_10082_10081_10110_10111_10112_10113_10114_10000089_10000086_10000083_10000041_10000044_10000080_10078_10079_10000038_10073_10000035_10070_10122_10123_10121_10126_10124-10503_10501,searchweb201603_2,afswitch_3,ppcSwitch_1,single_sort_1_default&btsid=0207e271-5f2c-489f-be15-a3aced211e7a&algo_expid=0eab590f-806a-4601-9f5c-1656aa91ca24-0&algo_pvid=0eab590f-806a-4601-9f5c-1656aa91ca24 https://www.aliexpress.com/item/3mm-Indoor-SMD0606-rgb-led-d... [2] https://twitter.com/ChuckMcManis/status/794023527720620032 https://twitter.com/ChuckMcManis/status/794023527720620032 [3] https://twitter.com/ChuckMcManis/status/794025248203022336 https://twitter.com/ChuckMcManis/status/794025248203022336 [4] https://1bitsquared.com/collections/embedded-hardware/products/1bitsy https://1bitsquared.com/collections/embedded-hardware/produc...

i336_ 10y ago
_Wow_, that is truly impressive. $3.7k for a ~2x1.5m² RGB (!!) display - and no added costs (besides a like <$50 interface controller setup). Nice! Hmm. I wonder what the weatherproofing (particularly heatproofing) on these things is like. I know of a time/temp display high up on a building (probably around 1x1.2m²) that is constantly corrupted, I'm wondering if it's the 40°C days around here (Sydney Australia) that keep hitting it... It's fascinating watching how QR encoding shifts and changes data - some of the time updates just adjust a few pixels, some of them adjust the whole barcode. I wonder what the source data for each frame was (but not terribly so). So... if I understand right, these are line-buffered? You send it a line's worth of data, hit "go", and it redraws that line? 240FPS is good, wow. One question: in the first couple of "ticks" of the second hand on the first clock video, I noticed how there appears to be a minor bit of "LED bleed" where some of the LEDs don't switch off for a couple fractions of a second. Curious, I had a look at the video frames: http://imgur.com/a/EVYB2 http://imgur.com/a/EVYB2. Is this an intrinsic problem in the driver system or perhaps a camera or encoding/compression glitch?
- hantusk 10y ago
  You can get an 80 inch TV for the same cost and roughly the same dimensions. I am curious to understand what this can offer that a TV can't
  - mschuster91 10y ago
    1) a LED "wall" is far brighter than a comparably sized TV, that's important when you place stuff high on a building 2) An ordinary TV is designed to be looked at from the front, a slight angle skews the colors and if it's extreme enough the screen gets totally unreadable. 3) A TV eats up tons of power, a LED wall not so much.
    - wnesensohn 10y ago
      Regarding point 3: At 150 modules consuming about 25W each, your LED wall is consuming about 3750W max. An 80" TV will consume about 300W. Power consumption of the LED wall will, however, be highly dependent on the displayed content. A white screen will consume most, a black screen basically nothing, but displaying only dark images is not exactly what LED walls are usually used for. The equation is simple: The brighter, the more power you'll need, and an LED wall is, as you say, far brighter.