Replacement for DM9374 or CA3161 decoder

Discussion in 'Electronics Resources' started by n4ft, May 29, 2008.

  1. n4ft

    Thread Starter New Member

    May 29, 2008
    4
    0
    Hi,
    I am looking for a replacement seven segment LED decoder for a project. I need the "-" (minus sign/hyphen) decoded and so far the only decoders I have found with it are obsolete. :(

    I found a CD4056B from Texas Instruments but it is listed for LCD and I need to drive 7 segment LEDs.

    Any info would be greatly appreciated.

    Thanks,
    Russ
     
  2. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    What exactly do you want to do? Maybe we can find a different solution.
    Do you have a single seven segment display for the numbers and another one to show the sign?
     
  3. n4ft

    Thread Starter New Member

    May 29, 2008
    4
    0
    I have three and four digit readout requirements. Plus one 8 digit that is a clock plus other information. I am hoping to be able to use a common readout board for all. Just omit the 4th digit for the 3 digit. Also combine two of the boards for the clock. The 4 digit readout needs a minus sign as the left hand digit and the clock needs a hyphen between the hours-minutes-seconds.

    The original units used the DM9374. I have the task of making new units with the same capabilities.

    I have looked into using a 5 x 7 matrix display but that doesn't match the look of the original display.

    This is for a Navy engineering propulsion trainer. Computer controlled simulation.

    Thanks,
    Russ
     
    Last edited: May 29, 2008
  4. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    Foe the hyphen between the hours-minutes-seconds you dont need a decoder, just connect them directly on the supply voltage as to have it on. Do you need it to pulse?

    For the minus sign you can use a RS flip flop to turn on/off the appropriate leds just to indicate the sign. Is it a counter which is controlled by up/down count pushbuttons?
     
  5. n4ft

    Thread Starter New Member

    May 29, 2008
    4
    0
    The 3 digit and 4 digit readouts are rpm / pitch. The 8 digit is used for a clock plus various other data readouts. I can't hard wire the minus. I wish I could. It would be very easy to wire that segment and let the computer light just it. I could do that for the 4 digit readout but the clock has to be able to display all 8 digits as 0 - 9. I originally thought that this was a piece of cake until I started looking for the decoder ic.
     
  6. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    Ok i see. You can make a logic circuit with gates which will turn off the decoder which drives the display on which you want to show the hyphen. Also this logic circuit will light the appropriate leds to show the hyphen. For all other combinations the logic circuit wont disable the decoder. However, the best solution will be a microcontroller. With a microcontroller you can build your own decoder, with every combinations you like to output and you can change it whenever you want.
     
  7. n4ft

    Thread Starter New Member

    May 29, 2008
    4
    0
    I am hoping to find the right decoder chip. I have 15 of these readouts to make and since they are driven by a computer I need to keep them as simple as possible. I am going to experiment with the 4056 chip and see if I can buffer it to drive the led. It is capable of the correct output.

    Thanks for the suggestions. I will continue to pursue these ideas. I have a little time to come up with something so it isn't a scramble yet.

    Thanks again,
    Russ
     
  8. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    Thats a lot easier if your chip outputs what you want. There are chips with buffers inside to boost your current capacity.
     
Loading...