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16x16 LED panel direct control

Hi all,

I got 10 LED panels of 16x16 LEDs each. Now I want to create a big modular display system with these and I'm also planning to post this on the instrucatbles website once I succeed. But I have some problems getting started. I spent alot of time reading all LED matrix related topics on the website here but none of the designs matches the fixed design I have on those panels. Instead of using some sort of multiplexing, 32 shift registers are used for 256 LEDs which means every LED has it's own shift register output.
Put then again, I also find 3 buffer ICs on the panels and I have no idea where they are used for... Below the info I have now:

1 PANEL:
- 16x16 yellow LEDs
- 32x M74HC4094B1 8-bit shift registers
- 3x 74HC125N Quad buffer/line register, 3 state

Pictures: http://www.myalbum.com/Album=64MKOUJR

First I want to work with only 1 panel and be able to control this by putting images on it. But for this I have to understand completely how the hardware is built up so I first want to create the schematic of 1 panel.

Can somebody help me with this and get me started on the project?

First goal: just control 1 panel with an AVR to put some text on it and let is scroll.
Final goal: be able to connect multiple panels and configure the software accordingly to the panels used. Then use a PC to put images on the screen and maybe even create a live feed (webcam capture). For this maybe an FPGA should be used to have more processing power/memory.

Many thanks already in advance!

kris_ge (author) 4 years ago
Hi all,

I just did the reverse engineering on a panel. As I said each panel has 2x 10 pin din connector, 1 for input and 1 for output. Actually they are exactly the same, only 1 pin is different. See the pin layout below:

1: OE (output enable)
2: CLK
3: DATA IN (for input connector) - DATA OUT (for output connector)
4: STR (Strobe)
5: Vcc
6: Gnd
7: Gnd
8: Gnd
9: Gnd
10: Vcc

So actually it is very simple. The first 4 pins match exactly the pinout of the used shift registers. Only 32 of them are cascaded.
So you can see 1 panel as 1 big 256 bit shift register with serial data in, CLK, strobe, OE and serial data out (to cascade more panels) and all these 256 parallel outputs drive 1 LED directly.
I already connected a panel to a frequency generator and tried to shift some bits in, and on a low f you see them move nicely. This confirms the regular working of a shift register. So now I'm at the next step, connect the panel to a microController and try to disply some stuff. Can anybody help me with building up the code for this so that is easily adaptable.

As a first testfase I just want to be able to show for example some letters or number on the panel, just in a static way.

I really hope that I can complete my first goal so I can make a nice instructable about it!

Greetings
Where did you get these panel? What kind of wiring do they have on them? Any idea of the power requirements of the panels?

You will need to sit down and figure out how these panels are wired up. You'll need to follow each trace and draw up a schematic of how it works or figure out what company made it and see about getting more information on them. Until you know how its all set up you won't be able to get it wired up properly and control it all. There isn't much anyone can do to help you online. Most of this has to be hands on work. Unless of course someone recognizes the panels and already knows what you need to make them work.

kris_ge (author)  mpilchfamily4 years ago
These panels came from old led pharma crosses. The ones you see on the outside of a pharmacy useless stuff like time etc.
But there is much more that you can do with them according to me! :-)

Power is no problem, I still have the power supplies from their original casing. But like you say, I will now first try to follow the paths (but it's very hard to see because of the coating on them) and draw a schematic. I thought that somebody maybe was able to recognize the design based on the components they used. Also a 10 pin din connector is used for every panel.

Will let you know once I have an idea of the schematic. But in the meantime all suggestions are welcome...

Thanks already for the quick reply!