1

the company i work for has tasked me in rebuilding an old LED sign we had replaced. (newer led rgb version) The driver board that was in the sign has gone out. So i am trying to rebuild the driver boards.

The boards are 8x8 for a total of 64 leds per board and 32 boards. I have done multiplexing of led's before the problem i am running into is that the board is NOT set up as the following.... LED

however, they are set up as the following enter image description here

As you can see they each have their own pin but share a common ground. I am having a problem finding something that can control that many leds at one time that can be expanded to 32 other panels.

I found the Mux Shield II over at sparkfun but i dont think its big enough to do what i want. What am i missing there has got to be something out there that will control 64 leds at a time!

Also the led boards are RED led's only. no RGB

Kelly Hansen
  • 11
  • 1
  • 1
    Your trying to rebuild 1 or 32 boards? What driver board went out? What IC did it use? – Passerby Aug 22 '17 at 02:59
  • I believe there is 32 panels in total so i need to build a driver for each one. The hardware they have has a hard glass like substances all over it (well the IC chips) and you can see much. Looks to be custom made and from talking to the company they claim to make them somewhere in the USA. I was thinking about controlling them via Arduino or raspberry pi. I was leaning towards the pi because i would like to use a nicer interface for the end user (this way i don't have to update it my self) – Kelly Hansen Aug 22 '17 at 03:29
  • I double check on the count tomorrow when i get to work – Kelly Hansen Aug 22 '17 at 03:30
  • 1
    I worked with ICs made by Seimens-OSRAM (just before Siemens sold OSRAM) that supported 128 LEDs per IC. These were used in pairs for each of three colors (6 ICs total in the module) for an RGB module with 256 RGB LEDs on it. That was 16 years ago. So I'm pretty sure such ICs are still around, though perhaps not in convenient packaging. You can see the modules I worked on here: http://www.infinitefactors.org/misc/images/p1000046_640x480.jpg Those are RGB LED modules using 5mm spacing and they dissipated 80 watts, in typical use. – jonk Aug 22 '17 at 05:54
  • 1
    there's led driver chips put there for 32 LEDs eg: LT3746IUHH, seems you'd need 3 or to do multiplexing if you want RGB – Jasen Слава Україні Aug 22 '17 at 11:31
  • Just confirmed there are 44 pannels in total. – Kelly Hansen Aug 22 '17 at 23:15

2 Answers2

1

I doubt there is an IC out there just for controlling 64 lines in a grid pattern.

Now, since you mentioned things like the Mux Shield, Arduino, and Pi in your question and comments, would 8 shift registers be sufficient? I know that this would work because I actually built a non-multiplexed LED array using 8 74HC595 shift registers and 64 individual wires to each LED (hand soldered, it was a lot of work). It was driven by an ATmega328p at 16MHz and there was no noticeable lag in the screen update.

I know this is not the ideal way to control an LED array, but given your situation of 64 individual wires, I think shift registers would be a feasible, and possibly the only way forward.

HaLailah HaZeh
  • 658
  • 5
  • 19
1

There is any number of led or segment driver that can handle this.

Just cause each LED has it's own anode pin does not mean you have to use it like that.

enter image description here

Simply tie the anodes together and drive them like that. Suddenly you have gone from 64 individual lines to drive, to 16. In the same exact 8x8 matrix configuration. Of course now you have to deal with scanning or multiplexing the displays.

Passerby
  • 72,580
  • 7
  • 90
  • 202
  • I don't understand how this would be doable as all the grounds are tied together? – Kelly Hansen Aug 22 '17 at 23:15
  • @Kelly hmm, your diagram made it seem like there was 4 grounds. I saw some other solutions and some were recommended in the comments. A picture is still helpful. – Passerby Aug 22 '17 at 23:20
  • Sorry about that i dont know why they did 4 ground pins but they did. I will take some pictures in the morning. – Kelly Hansen Aug 22 '17 at 23:33