Problem with CD4115BE

Discussion in 'Embedded Systems and Microcontrollers' started by spinnaker, Dec 1, 2012.

  1. spinnaker

    Thread Starter AAC Fanatic!

    Oct 29, 2009
    I ordered some CD4115 BCD to Seven segment decoders from Jameco.

    These decoders are really designed for CC displays but datasheet shows how they can be tied to CA displays. That requires a lot more components so I am using CC displays.

    According to the data sheet, I need to tie BI and LT high. LE needs to be low.

    If A,B,C,D and E inputs are tied high then all output segments are supposed to go high. In fact it works the exact opposite. I must make all the pins go low to get the segments to light.

    No matter what I do, I can not get segment g to light.

    The only way I can get g to light is if I tie LT low then all segments light from the light test.

    I have tried 2 different chips and same results on both.

    Am I doing something wrong? or do I have a bad batch of chips?

    Note: The input bus to the decoder is tied directly to LATC port of my pic.

    Last edited: Dec 1, 2012
  2. praondevou

    AAC Fanatic!

    Jul 9, 2011
    The truth table says the opposite. A,B,C,D High --> outputs low (not driving the LED).

    Not sure about the "g".
  3. spinnaker

    Thread Starter AAC Fanatic!

    Oct 29, 2009

    Man do I feel like a dim bulb. Thanks for turning on the light. :)

    This all makes sense now. It is a BCD decoder. Duh! :)

    I could have sworn I was seeing something different in that truth table. Must have been one of those senior moments. :)

    All is working now.