Need help changing numerical output to a bar graph display

Discussion in 'The Projects Forum' started by filonin_2, Jun 1, 2009.

  1. filonin_2

    Thread Starter New Member

    May 29, 2009
    Alright, I have this project I am working on. i am putting together this project for my car. It is called JAW (just another wideband.) It is a DIY wideband controller and display, that also can display EGT, boost and RPM with daisy chained displays.. I personally want to display Air Fuel Ratio, Exhaust Gas Temp, and boost. I am installing the kit into a DIN box, one of those little cubby holes that fit under your car's radio, so my area on the front for displays is limited. I could just barely squeeze the 3, 7 segment 4 character LED displays in there, but it would look a lot better if the AFR one was shown as a bar graph. Here is a link to the website The guy who makes these does not give out the schematics, but I know the wideband signal varies from 0-5V and that the display board uses a mc14489bpe to drive the display. I know that you can easily make a bar graph voltmeter using a lm3914, but I can't simply replace the mc14489bpe. I don't know much of anything about electronics, but the lm3914 doesn't have a data out so there would be no way to pass the data to the next display. My only idea is to use the output from the mc14489bpe to send a signal to the lm3914, but I don't know if that would work or how I would do it. Anyone have any ideas? Also, how would I attach a PDF?
  2. mik3

    Senior Member

    Feb 4, 2008
    Buy an LM3419 and a bar graph display and use the analog signal (0-5V) to drive.
  3. Bernard

    AAC Fanatic!

    Aug 7, 2008
  4. filonin_2

    Thread Starter New Member

    May 29, 2009
    Alright, on the mc14489, what pin(s) would I get the analog signal from?
  5. DC_Kid

    Distinguished Member

    Feb 25, 2008
    there are no analogs on the 14489. you need a DAC to either read the "data out" or piggyback off of the LED drive pins.

    i think what was suggested was to use the 0-5v of the sensor to feed a lm3419, then you would need to interpret the output as it relates to afr. perhaps with some minimal components it will be easier to display lambda.

    and i dont quite get the reference to mc14489. are you building something from scratch using that IC, or do you have the kit from the webpage you posted?
  6. filonin_2

    Thread Starter New Member

    May 29, 2009
    I have the kit from the website I posted, and I just wanted to change the way the info is displayed. Im pretty sure that I need to keep the mc14489 because of the way these displays are set up. There are 3 displays in my setup. AFR, EGT, and boost. The displays are daisy chained togther and they have to be wired in this order. W/o the IC, I don't think the display board for the AFR would be able to pass the remaining info to the next display board. Here is a picture of the completed display board for reference, this one isn't mine, I'm remote mounting the LED.


    I've gotten 3 small numerical displays that will fit for my project now, so for this one I'm not going to be using a bar graph anymore. but I would still like to know how it would be done because I plan on building another.