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  1. Join Date
    Oct 2002
    Posts
    2,716
    #11
    and here is the MAP sensor output characteristics


    note that high vacuum is on the left side of the plot where the output is nearly 3 volts ... so the bargraph should display full scale (all LED's lit) at this condition ... since the LM3914 is set for 1.25 volt full-scale at its input pin 5, you could expect the trimpot to be positioned just around the middle for proper calibration

    in my car, during idle, 6-7 LED's are lit ... all LED's lit up during deceleration ... no LED lits up when gas pedal is pressed hard ... i've used rectangular LEDs with red for 1&2, yellow for 3 to 6, and green for 7 to 10

    good luck!

  2. Join Date
    Oct 2002
    Posts
    150
    #12
    thanks sir kinyo! makaadaan nga sa deeco or alexan this weekend, hehe

  3. Join Date
    Sep 2004
    Posts
    4,933
    #13
    OT: those diagram reminded me of my pre-engineering days in college. wheew.

  4. Join Date
    Oct 2002
    Posts
    150
    #14
    eto datasheet ng LM3914 sa mga may kelangan:

    http://www.national.com/ds.cgi/LM/LM3914.pdf

    para naman sa LM3915

    http://www.national.com/ds.cgi/LM/LM3915.pdf


  5. Join Date
    Oct 2002
    Posts
    150
    #15
    Quote Originally Posted by Poops
    The circuit from endlessgwing uses a 3915 for logarithmic. My guess the sensor is likewise log based.
    yep, hindi linear yung output nung sensor dun sa site na nakita ko, dun sa figure 1 andun yung graph nung output nung sensor (voltage vs excess air factor)

  6. Join Date
    Oct 2002
    Posts
    2,716
    #16
    Quote Originally Posted by Poops
    You may have to add a limting resistor for each of the LED to keep the current to say 20mA. I usually use 220 ohms 1/4 watt depending on the LED. The sink rating I think is somehow limited.

    The circuit from endlessgwing uses a 3915 for logarithmic. My guess the sensor is likewise log based.
    The datasheet shows why resistors are not needed for the LEDs.

  7. Join Date
    Jan 1970
    Posts
    81
    #17
    Cool..no limiting resistors. Mindset ko kasi before was with thos LS245 drivers.

    Thanks. BTW, what 5V regulator are you planning on using (i.e. with a 12VDC input voltage)?

  8. Join Date
    Oct 2002
    Posts
    2,716
    #18
    Quote Originally Posted by Poops
    Thanks. BTW, what 5V regulator are you planning on using (i.e. with a 12VDC input voltage)?
    The one that comes in TO-220 package. It should work without heatsink.

  9. Join Date
    May 2004
    Posts
    84
    #19
    sir kinyo, nice project... patanong na rin... san ba MAP sensor ng civic? wala akong alam dun e... pwede rin bang makita yung led display mo? (yung finish product) tia!

  10. Join Date
    Oct 2002
    Posts
    2,716
    #20
    jepoy ... hirap akong sagutin ang tanong mo kasi nahihilo ako sa avatar mo!

    kunan ko muna ng pics yung mga gusto mo makita ... kapag nawala ang hilo ko bukas ... btw my project is not a finished product, when i saw that my prototype worked, had some fun watching the the display while driving, i didn't have the time to finally install it permanently so i shelved it ... i was happy enough that it worked

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