(Topic ID: 146346)

Monochrome RGB LED panels project

By Hawkulous

4 years ago

Topic Stats

  • 11 posts
  • 5 Pinsiders participating
  • Latest reply 4 years ago by Crash
  • Topic is favorited by 4 Pinsiders


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    #1 4 years ago

    Slightly different from the original RGB LED panels topic.
    I finally got some of the panels a bit more than a week ago and I thought it would be fun to build my own version of the colour idea on a micro computer that I own. I got sidetracked. What if you don't need a cpu to calculate the frames and whatnot? Would it possibly be the cheapest way to replace broken DMD's?
    First of all , I have limited electronic knowledge, and only the parts that I have in my house for the project, if you want to get involved post your findings/improvements here. I will include as much info as possible on building the circuit. The circuit is not perfect yet because I have run out of components and there is no electronic shop near me. The picture from the pinball machine needs syncing manually, I have tested STTNG,Shadow en TFTC. TFTC doesn't stay 100% in sync like the WB machines but I believe this can be overcome.

    Here is a video of STTNG and me syncing it.


    OK let me explain what is happening. All the signals are almost the same for both the LED panels and a traditional plasma DMD.
    The main difference is that the original DMD scans 32 rows of data per frame and the rows doesn't have to be addressed because they are scanned in the one after the other from 0 to 31 over and over. On the LED panels the scan is 2 portions of 16 and each one of the 16 lines must be addressed 0..15 (x2). The next semi big difference is that the pixel data on an original plasma DMD gets sent to the DMD as one signal, so one wire, because only one row of data is needed at a time, for the LED panels 2 rows of data get sent to the panel at once, one row in the top half and one row in the bottom half of the screen,so 2 wires (six actually, but we will just use 2).
    One more problem to overcome is the frame start signal from the pinball machine to the DMD, this is actually a problem related to my solution for the other 2 problems. But more later.
    The first 2 problems is easily solved by only supplying 1 line at a time to the led panels effectively changing them into 1/32 scan devices! This is accomplished by counting the lines and sending the first 16 rows to the top half of the screen and the second 16 to the bottom half. How? By using a counter that starts counting rows from 0-15 when the frame starts. Every time 16 is reached the signal gets sent to a different half of the LED panel. This is accomplished using a buffer for ic for one half and a transistor for the other half (all I had).
    A second counter is used to address the rows.
    The 3rd problem, the syncing is because of the way the framestart signal is used by the plasma DMD's effectively causing us to miss the address of the first row of every frame. The solution is to subtract 1 or add 15 to the address, but for this one needs a 4 bit full adder and I don't have one... at the moment. For now the signal has to be synced manually with a micro switch, click,click,click until the picture is in sync.

    #2 4 years ago

    Cool. How much do you think it'll be when you've got it all ready to go?

    #3 4 years ago

    My panels cost me $77 and the electronics will be about $2 and maybe it will work from the pinball machines power supply ,but an old pc psu will work just fine. For now it is just a project.

    #4 4 years ago

    Bravo. Although the cost of doing it with a microcontroller is pretty small compared to the panel cost, I love a good hack!

    It definitely won't work from the pinball machine's 5v supply, but you might be able to step down one of the other voltages.

    It looks like the 393 has 2 independent counters, so can't you just use one chip there?

    #5 4 years ago

    Hi ecurtz, I believe that in monochrome the panels will use 1/3 of the power for using white, and add to that the drop in scan rate from 1/16 to 1/32 it might be little enough!
    As for the counters the first 393 uses both counters and the second 393 zero at a different interval to the 1st one. Build it you will see!

    #6 4 years ago
    Quoted from Hawkulous:

    Build it you will see!

    Ha! Sounds fun, but I've got my own problems (thanks, Williams engineers from 25 years ago, way to ignore the specs).

    #7 4 years ago

    Wow! Now THERE is a topper!

    #8 4 years ago

    Very nice! This along with Pin2DMD will hopefully give us some nice options in the coming months.

    #9 4 years ago

    Yes the topper is growing on me! The photos and video doesn't do the picture quality justice, maybe somebody with some P2.5 panels can try and see if the circuit works with a different set of panels. The picture is quite bright, but it should be easy to dim it if needed. You can also have the panels display Red or Blue or combinations of the colours. I ordered a few parts, but it will probably be a while before I get them.

    #10 4 years ago

    Can you add adjustment pots for red, green, and blue drive for custom hues and brightness adjustment?

    2 months later
    #11 4 years ago

    Is this still in development?

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