3 x LM3914 with 3 x LED Bar, strange behavior. Correctly wired?

Discussion in 'Homework Help' started by ssommer, Jun 2, 2016.

  1. ssommer

    Thread Starter New Member

    Jun 2, 2016
    5
    0
    Hello Pros

    Honestly, i am a newbie. For a project i am trying to combine 3 x LM3914 Chips with 3 x LED Bars.

    I already tinkered a version with 1 x 3914 and 1 x LED Bar - it works quite good. I use some push buttons to bring the LEDs up and down (in the video you hear the push sound combined with the soundbard)

    In the last days i googled a lot about multiple LM3914 and also read some threads in this forums. For some reason the LED Bar have a strange behavior by trying to bring the LEDs up and down. Instead of counting up one-by-one the first click brings the whole bar up. Please take also a look on the video. I assume that i made mistakes with capacitor or resistors. I tried to adapt some knowledge which i became through my "1 x 3914" experiment.

    Currently i programmed it with my Arduino UNO, that every push-buttom will count up the voltage +0.40. I use the 5 Volt Output of my Arduino UNO.

    Could you have a look on my Fritzing Design? I hope you have some inputs where i have to look.
    There's a picture from my "1x3914" Project which works good. And the "3x3914" which does not want to work.

    Thank you guys!
    Sascha

    The Behavior of my 3 x 3914 Project



    The 3 x 3914 Project

    [​IMG]

    The 1 x 3914 Project
    [​IMG]
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,645
    2,344
    Hello,

    Can you post a schematic in stead of the connection diagram?
    Schematics are the real language for electronics.

    Bertus
     
  3. WBahn

    Moderator

    Mar 31, 2012
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    Are you debouncing your switches?

    If you are just trying to make the three displays identical to each other and to the original single-display circuit, why are you running them in different modes (i.e., why is Pin 9 connected differently)?

    Do you have bypass capacitors on each IC?
     
  4. WBahn

    Moderator

    Mar 31, 2012
    17,715
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    What, exactly, are you trying to achieve? The LM3914 has several modes of operation. Have looked carefully at the datasheet to see how to implement the mode you want?
     
  5. AlbertHall

    Well-Known Member

    Jun 4, 2014
    1,889
    375
    Quick look - you have pin 4 of the right-most LM3914 connected to 0V which messes up the reference chain.
     
  6. AlbertHall

    Well-Known Member

    Jun 4, 2014
    1,889
    375
    All three pin 9's are connected to +5V.
     
  7. WBahn

    Moderator

    Mar 31, 2012
    17,715
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    Not in the original circuit -- look at the diagram, it is floating.
     
  8. AlbertHall

    Well-Known Member

    Jun 4, 2014
    1,889
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    I see what you mean - the '1' version is dot mode and the '3' version is bar mode. That won't stop it working though.
     
  9. WBahn

    Moderator

    Mar 31, 2012
    17,715
    4,788
    Depends on what "working" means. The TS said that the 1-unit circuit worked fine but that when he tried to expand it to three units it didn't. If he was expecting it to work like the 1-unit circuit did (i.e., in the same mode) but is operating it in a different mode, then even when he does solve the other problems with the reference chain it will still appear not to be working according to his expectations. I would also argue that getting the mode correct trumps getting the reference chain correct (from a sensible debugging standpoint).

    But we can't tell what he needs to do until he lets us know what he wants to have happen.
     
  10. ssommer

    Thread Starter New Member

    Jun 2, 2016
    5
    0
    Thanks already for your help!! I really appreciate that!

    I will come back in a few hours back. I am finishing the schematic (the autorouting function not really helped me) and i will post it and some additional informations.
     
  11. ssommer

    Thread Starter New Member

    Jun 2, 2016
    5
    0
    Hi

    I've tried to design a schematic view.

    [​IMG]

    I am not fully understand. Why Pin 9 is connected differently? They should not be connected all together to V+ ?

    Yes, for the 1-LED Bar it works. Please have a look on my Video about it (ignore the spoken words... :) i shot that video 2 weeks ago for a colleague).

    There i have 3 Buttons
    1 Button to bring the Leds up
    1 Button to bring the Leds down
    1 Button to trigger a Fire-sound according to the current amount of LED which are glowing



    I am trying to achieve now the same. But for 30 Leds with 3 x LM3914. With the Arduino i can manage the Voltage to bring the LEDs up and down. The only problem seems to be my wiring.

    When the whole electronic stuff is finished, i want to install that in a Movie Prop Rifle (Mark 3 Phaser Rifle from Star Trek)

    In the other way. The 1-LED Bar Version is in Bar Mode. The 3-LED Version a - unwanted - combination both of them. But you are right, i forgot in the 1-LED connection diagram the connection to 5V
     
  12. AlbertHall

    Well-Known Member

    Jun 4, 2014
    1,889
    375
    Looking at your layout diagrams and the schematic you have posted the 1 LED version has pin 9 unconnected while the 3 LED version has all 3 pin 9's connected to supply. According to the data sheet I looked unconnected is dot mode while connected to supply gives bar mode.

    Your schematic fails to connect the input signal to all three LM3914's.
    Both the schematic and your layout diagram show a connection to 0V from pin 4 of IC3 which will stop the reference working properly. Remove the link marked on this diagram.

    upload_2016-6-2_22-0-51.png
     
    ssommer likes this.
  13. ssommer

    Thread Starter New Member

    Jun 2, 2016
    5
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    You are right, on my connection diagramm above i forgot to draw the line for Bar Mode.

    Thank you! I will check that this evening
     
  14. ssommer

    Thread Starter New Member

    Jun 2, 2016
    5
    0
    That was the solution! Thank you for your hint and help!

    Here you can see the result :)
     
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