Voltage divider problem for LED level display

Discussion in 'The Projects Forum' started by jj_alukkas, Dec 10, 2010.

  1. jj_alukkas

    Thread Starter Well-Known Member

    Jan 8, 2009
    751
    5
    Hi everyone,

    I need a little help in modifying my circuit for a led level indicator. I'm using a KA2284 chip which is normally used in vu meter's in audio systems to build an RPM indicator for my motor bike.. I just need an apporximate engine speed indicator as 5 led's taking the alternator's rectified voltage as
    reference.. The circuit is the test ciruit in the attached pdf file, figure 2. The only difference is that i am using a cap on the input even though they told to neglect when using a dc input.. Also the fixed resistance after the cap is 22k and I added an additional 1Meg variable preset to compensate and drop for the ~12v input..Vcc is from battery with a 5v regulator.. Multimeter indicates a voltage variation between 13v to 14.8v DC on the line when the bike is idling as well as revved to a moderate rpm.. On testing the circuit, one or two of the level indicator led's can be made to light up, but on opening the throttle further, only one more led lights up for the corresponding increase in voltage.. In other words, I cant scale the led's properly to light the 5 leds for my input voltages. Anything I can do to achieve this? Thanks a lot for any help!!
     
  2. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,783
    943
    The Cap on the input BLOCKS DC levels, therefore it MUST be shorted across with a DC input. (As the Data Sheet says). It is feeding an op amp input.
     
    jj_alukkas likes this.
  3. jj_alukkas

    Thread Starter Well-Known Member

    Jan 8, 2009
    751
    5
    Thanks for that, but Will that fix this prob? sorry if I seem too lazy to test, but for each test I have to remove my bike's front cowl, so it takes time.. will test anyway tomorrow.. I used the cap as I first tested it on a 12v battery and worked good..
     
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