Another question about led show Vin

Discussion in 'The Projects Forum' started by david1234, Jan 6, 2014.

  1. david1234

    Thread Starter Member

    Nov 27, 2013
    81
    1
    I have ask here before about LM3914, and someone show me a working device with this IC - Max924
    http://datasheets.maximintegrated.com/en/ds/MAX921-MAX924.pdf

    I have seen in figure 7 - that it can show me status of Vin in 4 leds
    from I understand that if I have Vmax=12V I'll use R1=10K,R2=110K
    and then all the LEDs will be on .
    my question is what do I need to change in order to make the steps work other way? my Vin is change between 10.0<Vin<12(so every drop of 0.5V - 1 led will turn off)
    the IC will work when I press a reset button,and the power he will get from the battery he is checking.

    possible ?

    Thanks ,
     
  2. BillB3857

    Senior Member

    Feb 28, 2009
    2,400
    348
    What if you tied the reference to the + inputs and the resistance divider to the - inputs?
     
  3. david1234

    Thread Starter Member

    Nov 27, 2013
    81
    1
    let me see if I understand -
    connect the battery (which I'm testing 10-12V) to PIN8 and R=182K (as shown in the datasheet) , and then take the point between R1 and R2 and connect it to PIN9?
     
  4. BillB3857

    Senior Member

    Feb 28, 2009
    2,400
    348
    NO! DO NOT CONNECT BATTERY TO PIN 8 UNLESS YOU WANT THE MAGIC SMOKE TO COME OUT!!!

    Instead, reverse the input to each of the individual comparator sections. Move wire for pin 4 to pin 5 and wire from pin 5 to pin 4. Likewise, reverse the inputs to each of the other comparators.
     
Loading...