4 ms·

LED multiplexing layouts for hand-crafting

72 points by dcschelt 7y ago

tinus_hn 7y ago
Clever. You could also use a ring shifter so you only need reset and clock for one of the rows.
frob 7y ago
This is an interesting idea. However, I feel like this could be better addressed by using an addressable chip like the ws2811. These can be chained for quite the distance and you will not get the inherent flickering that comes with the multiplexing approach. They even come in a standard LED form factor with one additional leg for data. This can all be controlled with a single digital pin on an arduino using a library like fastLED.
- rowanG077 7y ago
  Multiplexing doesn't have to flicker if you do it fast enough.
  - crtlaltdel 7y ago
    ^truth, insofar as you cannot detect the flicker
- XzAeRosho 7y ago
  I'm a hobbyist when it comes to RPi/Arduino projects, and I always feel powerless when I do projects like these. There's always a better way to do what you're currently doing, without too much extra costs, and there's no way I could have found out on my own. It happens almost the opposite when building software (maybe because that's what I do for a living?), but it makes me think that maybe there's a different workflow that I'm not aware of when working on HW projects.
  - watersb 7y ago
    Like anything else, just do it. You start somewhere, and gain experience.
  - shezi 7y ago
    Don't worry too much about it, there's merit in doing any of the levels anyway. Doing it the way from the article is much closer to the metal than using ws2812 or neopixels. These programmable rgb LEDs are quite complicated, they contain a shift register, three DACs and three LEDs, but they're super convenient if you want to place lights anywhere. I suggest you look at esp8266 and micropython, if you want to get a quick start. You can get them rather cheaply on aliexpress, along with ws2812 strips. Or you get them from adafruit, which is much quicker but more expensive. Adafruit calls the LEDs neopixel, so Google for that too. And of course you can message me or anyone here at any time. Doesn't mean we're experts, but we'll help as much as we can.
- jdsully 7y ago
  Seems rather expensive to use so many ws2811s.
- nixpulvis 7y ago
  That's cool too, but there's something awesome about seeing the whole circuit down to the multiplexing and discrete LEDs. Granted addressable LEDs like the ws28xx do pass data in a cool way, and allow awesome and somewhat easy projects.
- robert_foss 7y ago
  Smart LEDs have some serious drawbacks apart from cost. For example you can expect a single WS2812 to draw 1mA, even when it is off and is receiving no signal. This makes it unsuitable for low power wearable applications.
nixpulvis 7y ago
I've been (slowly) working on an 8x8x8 led cube. I'm also soldering all the LEDs together in a somewhat custom way (not a cool diagonal pattern tho). Here's a photo: https://imgur.com/gallery/YjSmFrb https://imgur.com/gallery/YjSmFrb

72 points by dcschelt 7y ago

Clever. You could also use a ring shifter so you only need reset and clock for one of the rows.

frob 7y ago

This is an interesting idea. However, I feel like this could be better addressed by using an addressable chip like the ws2811. These can be chained for quite the distance and you will not get the inherent flickering that comes with the multiplexing approach. They even come in a standard LED form factor with one additional leg for data. This can all be controlled with a single digital pin on an arduino using a library like fastLED.

rowanG077 7y ago
Multiplexing doesn't have to flicker if you do it fast enough.
- crtlaltdel 7y ago
  ^truth, insofar as you cannot detect the flicker
XzAeRosho 7y ago
I'm a hobbyist when it comes to RPi/Arduino projects, and I always feel powerless when I do projects like these. There's always a better way to do what you're currently doing, without too much extra costs, and there's no way I could have found out on my own. It happens almost the opposite when building software (maybe because that's what I do for a living?), but it makes me think that maybe there's a different workflow that I'm not aware of when working on HW projects.
- watersb 7y ago
  Like anything else, just do it. You start somewhere, and gain experience.
- shezi 7y ago
  Don't worry too much about it, there's merit in doing any of the levels anyway. Doing it the way from the article is much closer to the metal than using ws2812 or neopixels. These programmable rgb LEDs are quite complicated, they contain a shift register, three DACs and three LEDs, but they're super convenient if you want to place lights anywhere. I suggest you look at esp8266 and micropython, if you want to get a quick start. You can get them rather cheaply on aliexpress, along with ws2812 strips. Or you get them from adafruit, which is much quicker but more expensive. Adafruit calls the LEDs neopixel, so Google for that too. And of course you can message me or anyone here at any time. Doesn't mean we're experts, but we'll help as much as we can.
jdsully 7y ago
Seems rather expensive to use so many ws2811s.
nixpulvis 7y ago
That's cool too, but there's something awesome about seeing the whole circuit down to the multiplexing and discrete LEDs. Granted addressable LEDs like the ws28xx do pass data in a cool way, and allow awesome and somewhat easy projects.
robert_foss 7y ago
Smart LEDs have some serious drawbacks apart from cost. For example you can expect a single WS2812 to draw 1mA, even when it is off and is receiving no signal. This makes it unsuitable for low power wearable applications.

nixpulvis 7y ago

I've been (slowly) working on an 8x8x8 led cube. I'm also soldering all the LEDs together in a somewhat custom way (not a cool diagonal pattern tho). Here's a photo: https://imgur.com/gallery/YjSmFrb https://imgur.com/gallery/YjSmFrb