LED Light board!

Discussion in 'The Projects Forum' started by KringleFantastico, Jan 19, 2013.

  1. KringleFantastico

    Thread Starter New Member

    Jan 19, 2013
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    Dear all,

    Please forgive my ignorance. I am a professional in a completely unrelated field, but completing this project would help me tremendously. I would like create a "simple" LED light board. I have tried poking around on the internet for some help with this, but I am not even sure how to frame the question so that nonspecific results are not returned by google. I am nearly positive that someone has done something like this before, and as such, I would be more than happy to receive direction to similar posts. So... my project is as follows.

    I need to make an led light board, with a 10x10 grid of LEDs. The board will be connected to a button for controlling the progress of the lighting scheme. The board will have two modes of function. For the sake of this discussion, the board will be labelled as rows (letters) and columns (numbers). The board should be powered by a smallish battery.

    Mode one will light the next LED in sequence upon clicking the button. This means that when the board is turned on, initially position A-1 is lit. Click the button, A-1 turns off, and A-2 turns on. At A-10, the sequence will cycle to B-1. This will continue until J-10, at which point, another click will once again light A-1.

    Mode two will light an entire row at one time. So by switching from single cell progression to whole row progression, the board will initially light with row A lit. Upon clicking the button, row A turns off and row B lights up. This continues to J, and again cycles back to A.

    Two additional features would be really awesome to have. The first is to expand the board (essentially to 11x11) so that a heading for the rows and columns may be lit while the individual cell is lit. If for example, one is to click the button and C-7 is lit, a heading letter for the row (on the far left side) will also be lit, as well as the heading for the column (at the top of the board) will be lit as well. The second feature would be to have the button communicate with the board wirelessly.

    So that's it. Sorry to be completely ignorant about all of this. I am pretty sure this is kid's stuff, but it is new to me. Many thanks in advance for any advice.

    Best,

    Kringle
     
  2. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    This is a job for a microprocessor.. Feel like learning to code?
     
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  3. KringleFantastico

    Thread Starter New Member

    Jan 19, 2013
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    Hmmm... I was thinking that this might be the case. I was going to go over to our computer science department on Tuesday to bug them, and see what they think about this. Learning to code wouldn't be so bad. Even so, I would imagine that this would be a reasonably simple routine that someone, at some point, has posted to the web. Thanks for the reply.
     
  4. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    Here is a sample layout to get an idea of connections

    There isn't really a way to do what you are asking without using a microcontroller (or a ton of logic ICs + drivers). A discrete/transistor + switch solution would be financially unfeasible.

    That layout is for a scrolling sign, but the LEDs could be re-arranged to a 10x10 matrix, all driven by a single PIC microcontroller + shift registers.

    It is possible to do a 10x10 matrix from a single PIC without shift registers using "charlieplexing", but the wiring and code gets a bit more complicated. Charliplexing uses the behavior of LEDs (one way operation) to drive more than one LED from each set of I/O lines.
     
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  5. vrainom

    Member

    Sep 8, 2011
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    If I were to do this I think I would go for a pair of cascaded decade counters 4017 one for the columns and one for the rows plus twenty npn transistors ten as emitter followers for rows and ten driving the columns much like the schematic thatoneguy linked.
     
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  6. KringleFantastico

    Thread Starter New Member

    Jan 19, 2013
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    Thatoneguy,

    Thank you very much for the reply. This is exactly what I was looking for. I am a research biologist, and so this is really far afield from what I usually get myself in to. That said, I am also pretty good at "figuring things out", so long as I have a starting point of some kind. Thanks again.
     
  7. KringleFantastico

    Thread Starter New Member

    Jan 19, 2013
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    As I mentioned above to Thatoneguy, thanks for the help. I really appreciate it. These are great keywords to help me navigate the google machine and get started on the project.
     
  8. wayneh

    Expert

    Sep 9, 2010
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    "Smallish" is obviously a subjective term, but these two desires could be in conflict. Lighting 10 or 11 LEDs takes a bit of juice. It's certainly doable - you can buy a 28 LED flashlight powered by just 3 AAAs - but it's something to consider.
     
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  9. KringleFantastico

    Thread Starter New Member

    Jan 19, 2013
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    Absolutely. I will be sure to take this into account when planning the device. Three AAA batteries is reasonable for my purposes, but smaller is always better. Thanks for the advice.
     
  10. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    You'll only be powering at most, 1 row at a time, the PIC will multiplex the display, so the max load will be 10LEDs in parallel. You should run it at 4.5V or 5V, as 3.3V (newer microcontrollers) isn't enough to light a White LED, which usually has a Vf around 3.5V.

    The other item not shown in that schematic is current limiting, you'll want to add a resistor appropriate to the voltage out so current does not exceed 15mA or so. New LEDs are very Bright, even at 10mA, when used in a display (vs flashlight).
     
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  11. wayneh

    Expert

    Sep 9, 2010
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    I was just nudging against any thoughts of using "smallish" button cells instead of AAs or AAAs, which should be fine.
     
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  12. Harryroberts

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    Jan 21, 2013
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    You need to take help of some coder who have good knowledge of embedded system
     
  13. John P

    AAC Fanatic!

    Oct 14, 2008
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    I believe the way to do this is with matrix driver chips like the MAX7219. Each of these can run 64 LEDs, so 2 of them would give you 128 LEDs, which would run your 11x11 array plus a few extras. The drive to the chips is a serial protocol which lots of small processors have built-in, though it's also easy to simulate by explicitly operating output pins.

    Does this really need to be built from scratch? It would be way less work and money if you used a computer display, and the "pushbutton" could be the space bar. If there's additional hardware involved, it's not too hard to set up interfaces from the computer to drive it.
     
  14. samjohns

    New Member

    Jan 20, 2013
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    i thought that as he described it only 3 LED's will be lit at any 1 time ( if outer reference LED's are also used to show a crossing point of the matrix of where the actual led is lit) ....unless the row lighting is included and then that will be max 10 LED's.

    But if you just need to define row and column ...you could just use 10 LED's across and 10 down to specify row and column. Like on an electronic chessboard. B5 D8 etc. This would only require 2 LED's lit at an time to represent all 100 positions. Unless you also had to have the actual single LED's lit.
    As far as the whole row being lit you could have an LED of another color at left of all the rows that would light to represent the entire row being lit.

    Just some thoughts I had. to pull down the parts and power required. Unless of course you needed the full visual you described.
     
  15. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    What distance does this need to be viewed from?

    10"x10" - about 1 ft²/m² or 10'x10' - about 10ft²/3m²?

    If you need it displayed large, or want to label the LEDs (Cells), you'll want to put them into boxes about 10" square, with diffusion plexiglass on the front side so that box 'glows' instead of acting like a focused point light.

    For any display you'd want to get diffused wide angle LEDs, or just sand the round lens off the front of a narrow LED and make the entire clear surface hazy with a 3M ScotchBrite pad.

    Advantages of large display: For a classroom, 300 people could see it and nobody directly in front would be blinded.

    Advantages of a small display: Lights closer together and portable.

    Disadvantages of a Large display: Not Very Portable

    Disadvantages of a Small display: Only effective for small groups, and will be blinding for those directly in front if the LEDs aren't sufficiently dimmed and diffused.
     
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