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  #1  
Old 09-30-2013, 05:22 PM
jayeshvc777 jayeshvc777 is offline
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Default f to v converter using LM331

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

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
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  #2  
Old 09-30-2013, 06:10 PM
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ronv ronv is offline
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Is your input voltage 0 to 15 volts? OR ?
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  #3  
Old 09-30-2013, 07:11 PM
tshuck tshuck is online now
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Did you read the datasheet, as opposed to some random image?
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Old 10-01-2013, 05:43 PM
jayeshvc777 jayeshvc777 is offline
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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..
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Old 10-01-2013, 06:07 PM
jayeshvc777 jayeshvc777 is offline
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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.....
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  #6  
Old 10-01-2013, 06:42 PM
wayneh wayneh is online now
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FWIW, that circuit comes from Figure 17 of the TI data sheet.



Perhaps you should supply a photo of your build. There's likely an error. Either that or the IC is dead.
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Old 10-02-2013, 11:50 AM
jayeshvc777 jayeshvc777 is offline
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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
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Old 10-02-2013, 01:26 PM
wayneh wayneh is online now
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Quote:
Originally Posted by jayeshvc777 View Post
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?
Yes, but the generator must share a common ground with your circuit.
Quote:
Originally Posted by jayeshvc777 View Post
2) where i need to see o/p - multimeter or CRO
A multimeter should be fine.
Quote:
Originally Posted by jayeshvc777 View Post
3)is vs is kept strickly +15volt?
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.
Quote:
Originally Posted by jayeshvc777 View Post
4)in Rs i should connect 5 ohm resistor or a potentiometer ?
A fixed resistor, say 2.7K, would work, but the 5K pot
allows for adjusting the output.
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Old 10-02-2013, 05:35 PM
jayeshvc777 jayeshvc777 is offline
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thanks for the info,i will b trying this tomorrow so i will let u knw......thanks again.
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  #10  
Old 10-03-2013, 12:11 PM
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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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