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I would like to embroider with electroconductive yarn and I need to light up 25 LEDs but they should work individually (not light up at the same time) and I can use only 10 pins. I cannot use any other IC's as my board is limited. I am using Microbit to light up the 25 LEDs using 10 pins.

If I connect all the positive column of LED 1,2,3,4,5 in with a single pin and then connect all the negative rows of LED 1,2,3,4,5 with another pin then there is always a problem of overlapping with the positive as they can have short-circuit since I am using embroidery machine to stitch electroconductive yarns.

How can I make a bridge between column of LED1 with row of LED2 without actually touching them? enter image description here

How can I control the LEDs individually?

Note that I am not allowed to use any other IC's or shift register or anything else. I have heard about Charlieplexing but I am not sure if I can control the LEDs individually.

winny
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James Smith
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    have you considered addressable LEDs? – jsotola Jun 14 '23 at 14:51
  • There are two interpretations to *individually*: light 1) exactly one, potentially none at all 2) any combination of LEDs, including 0 and 25 for more than 33.5 million patterns. Please state which. – greybeard Jun 14 '23 at 15:30
  • Charliplexing will allow you to control arbitrary individual LEDs, but you are still stuck with the reduction of brightness due to multiplexing. Crossing conducting yarns without shorting is a different problem - I'm sure you've come across the '3 houses 3 utilities' puzzle where the gas, water and electric supplies must serve all three without crossing, can't be done, and 5 is worse. You might be able to put drivers onto the garment, but then you might as well use a daisy-chain of fully addressable LEDs – Neil_UK Jun 14 '23 at 15:58
  • Is it possible to use zero ohm resistors (jumpers) as bridges? – Jens Jun 14 '23 at 16:03
  • @jsotola No i didnt considered addressable LEDs even if i do, how do i solve the problem with the overlapping of positive and negative connections which is embroidered – James Smith Jun 15 '23 at 07:30
  • @Neil_UK So controlling a 5x5 LED matrix individually using daisy chaining and only 10 pins, it might be challenging to achieve without additional hardware. The reason is that each LED in the matrix requires two pins—one for the anode (+) and one for the cathode (-). In a traditional LED matrix, you would have a total of 25 LEDs (5x5) requiring 50 pins (25 for anodes and 25 for cathodes) to control them individually. However, if you want to reduce the pin count to 10, you would need to utilize additional components like shift registers or LED driver ICs. – James Smith Jun 15 '23 at 08:01
  • @JamesSmith for 25 LEDs, you only need 6 wires Charliplexed, in fact 6 will take you to 30 LEDs in a 5x6 matrix, for which you can have up to 5 on in any one multiplex epoch, giving you only a 6:1 brightness reduction for an arbitrary display. The 'extra hardware' is limited to higher current drivers, needed for any multiplex arrangement. But, you need to cross wires. If you forbid crossing wires, then it gets to be a whole more complicated problem, putting the required fanout devices on the fabric. – Neil_UK Jun 15 '23 at 08:07
  • @JamesSmith the question about insulating the wires should be posted separately ... this is a Q&A site ... the "Question" must be answerable with one "Answer" ... if someone gives you a good answer about controlling the LEDs, and someone else gives you a good answer about insulating the connections, then which one will you choose as the correct answer? – jsotola Jun 15 '23 at 16:32

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