f to v converter using LM331

Discussion in 'The Projects Forum' started by jayeshvc777, Sep 30, 2013.

  1. jayeshvc777

    jayeshvc777 Thread Starter New Member

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    actually i dont know anything about LM331 and how it works as freq to vltg convertor ,so guyz plz help me for this project as soon as possible.
    I followed 1 ckt frm google,which is displayed in this post plz look after that and plz give ur views because i implemented this ckt but there was no o/p [​IMG]

    i used function generator at input side and multimeter at output, but there was no output for any variation in frequency (100hz-100khz)

    as i said i dont know much about it so plz help me out for this project and if there is another ic or some ckt plz post it

    thank you for reading......and plz reply:):):)
  2. ronv

    ronv Senior Member

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    Is your input voltage 0 to 15 volts? OR ?
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  3. tshuck

    tshuck E-book Developer

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    Did you read the datasheet, as opposed to some random image?
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  4. jayeshvc777

    jayeshvc777 Thread Starter New Member

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    first of all thanks for reading & replying this thread.......actually i badly need help to complete this project.
    ronv- from the image i provided, i have given frequency ranging from 1khz to 100khz from function generator at pin 6, a +15v dc as mentioned in the image and multimeter at pin 1 to check voltage o/p,but problem is such that there is no output at any given frquency
    see as i told i dont have much info about this ic LM331 and the circuit
    so plz see the circuit and tell me what is going wrong.....plz
    i may be completely wrong so please check the circuit and post me as soon as possible......thanks..
  5. jayeshvc777

    jayeshvc777 Thread Starter New Member

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    tshuck thanks for replying actually i took a random image from a site called circuitstoday ......and plz help me for this this circuit.....
  6. wayneh

    wayneh AAC Fanatic!

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    FWIW, that circuit comes from Figure 17 of the TI data sheet.

    [​IMG]

    Perhaps you should supply a photo of your build. There's likely an error. Either that or the IC is dead.

    Attached Files:

  7. jayeshvc777

    jayeshvc777 Thread Starter New Member

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    wayneh- thanks for replying, i looked over circuit which u provided. i need to know more about following things plz
    1) about i/p- Is it ok if i give frequency from frequency generator?
    2) where i need to see o/p - multimeter or CRO
    3)is vs is kept strickly +15volt?
    4)in Rs i should connect 5 ohm resistor or a potentiometer ?
    soon i will tag photo of my build circuit
  8. wayneh

    wayneh AAC Fanatic!

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    Yes, but the generator must share a common ground with your circuit.
    A multimeter should be fine.
    I think the voltage needs to be regulated but I don't think it has to be 15V. But you might need to change some of the biasing resistors if you use a different supply voltage.
    A fixed resistor, say 2.7K, would work, but the 5K pot
    allows for adjusting the output.
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  9. jayeshvc777

    jayeshvc777 Thread Starter New Member

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    thanks for the info,i will b trying this tomorrow so i will let u knw......thanks again.
  10. SgtWookie

    SgtWookie Expert

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    Note that there is a rather significant difference in the output cap size between the two schematics. 1uF (in the datasheet schematic) is equivalent to 1,000,000pF, or 10,000 times greater than the 100pF in the first schematic. That shouldn't affect whether the IC is working or not, but it certainly will make the output more stable, particularly in the lower frequency ranges.
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  11. jayeshvc777

    jayeshvc777 Thread Starter New Member

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    so which cap would b perfect 1microf or 100pf.....??????
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