Shufflebd Scoreboard w/ 5" 7 Segment LED's

Discussion in 'The Projects Forum' started by txcamaro94, Sep 14, 2008.

  1. txcamaro94

    Thread Starter New Member

    Sep 14, 2008
    OK this is my second time trying to post this hit the wrong button and lost everything.
    I'm building (trying) a score bd for my brother's shuffleboard table, it will consist of 4 sets of 2 digits 5" displays (non multiplexed). 1 set 2 digit per side per team A and B with the opposite side displaying the same scores on it's 1 set 2 digit displays. With that said I'm having problems even powering up one of these displays (common anode). I have my circuit breadbd using a small 7 segment to test the rest of the circuit. After many issues with debouncing I've got it working for the most part. What I have is 2 different designs but neither seem to drive these large displays.
    1st design:
    Counter HD74LS192p syn up/down counter
    SN7447an BCD to 7 Segment decoder driver
    MC14093B Quad 2-input NAND Schmitt Trigger (debounce)
    I know the 7447 can sink up to around 40mA but only can turn on the DP and Comma.

    2nd design:
    Counter MC14029 up/down counter
    MC14511B BCD-7 seg latch/decoder/driver
    MC14093B Quad 2-input NAND Schmitt Trigger (debounce)
    On this circuit I was thinking I needed use switching transistors for the output of the decoder as it's active high outputs aren't what's needed for the common Anode displays. If this is what would be needed how would I hook them up limiting resistor values and so on. :confused:

    The 5" 7 segments specs are:
    @ 20mA Electro0 Optical data: Forward voltage typical 9.25v max 11v
    Max Ratings: Pulse current (lfp)150mA, DC forward current (lf) 25mA

    Again I'm not stuck on using either of these circuits or something new just trying to use the expensive x8 5" displays I've already purchased.

    Any help for this rookie would be appreciated. :eek:
    Last edited: Sep 14, 2008
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    You will need a current limiting resistor in each of the 7 segment lines between the 7447 and the displays. I don't know what voltage you're using to the common anode, but 1000 ohms will be a safe value for testing.

    You have two inputs that have to be in known states for proper operation - the lamp test and the ripple blanking. The lamp test (pin 3) should be tied high through a 4.7K resistor. The RBI (pin 5) has to be pulled low.

    Original TTL has to have all inputs at known levels, or they will tend to oscillate at the point where they switch from high to low. The chip may behave strangely or even overheat and fail. TTL has to be pulled up through a resistor, as a failure in that input can short the power supply.
  3. hgmjr


    Jan 28, 2005
    Can you post a schematic of your design as it currently exists?

  4. txcamaro94

    Thread Starter New Member

    Sep 14, 2008
    It's all chicken scratch right now I'm trying to clean it up but the focus of my questions revolve around the large LED 7 segments. I'll post once I clean it up.
  5. txcamaro94

    Thread Starter New Member

    Sep 14, 2008
    Has anyone had a chance to look at my Schematic, hopefully you can read it. I'm having all kinds of problems driving the 5" 7 segments the rest of the counting circuit works great.