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Trouble with LM567

Discussion in 'General Electronics Discussion' started by George O'Brien, May 26, 2014.

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  1. George O'Brien

    George O'Brien

    5
    0
    May 26, 2014
    Hello,

    I am trying to get an LM567 to respond to an output from a 555 timer in the astable mode. The R1 and C1 for the LM567 are 10KHz and 6.1uF. The other components are the same as on the data sheet in the drawing with the multiple tome decoders (I'm just using one of these tone decoder circuits). I may have damages the LM567 because the voltage I measured on the input was about 8VRMS which would give a peak voltage higher than the max tolerable on that pin. I lowered the voltage with a voltage divider but there was still 6 VRMS on the input although the divider output was 1VRMS. I don't know why. I don't have a scope. The LM567 output doesn't go low for any frequency in the range the 555 was set for. I will try to provide a schematic, but I need a little more time. I don't have a working scanner or cad software.

    George
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,418
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    Jan 21, 2010
    Paintbrush works. Also there are several tools available on line
     
  3. George O'Brien

    George O'Brien

    5
    0
    May 26, 2014
    Thanks but I'll wait until I get access to a scanner.
     
  4. George O'Brien

    George O'Brien

    5
    0
    May 26, 2014
    I got access to one.
     
  5. George O'Brien

    George O'Brien

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    0
    May 26, 2014
    Here it is. Sorry It is upside down. Perhaps I will have to return to the library to rescan it.
     

    Attached Files:

  6. duke37

    duke37

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    Jan 9, 2011
    And here it is if you are in Australia!
     

    Attached Files:

  7. George O'Brien

    George O'Brien

    5
    0
    May 26, 2014

    Thanks but just in case I rescanned it and here it is:
     

    Attached Files:

  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,418
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    Jan 21, 2010
    With the components you have chosen, I calculate the capture frequency is about 14kHz.

    The frequency is approximately 1 / (1.1 * R1 * C1)

    See here.

    Perhaps this is your problem? (possibly not, since the 555 should oscillate at between 13kHz and 16kHz based on your stated components.

    My concerns with the 555 oscillator is that you are using a very low value capacitance. Any leakage could easily change the frequency significantly (as could stray capacitance). I recommend you increase your capacitor by a factor of 10, and reduce the resistors by a factor of 10.

    I note that your C2 is larger than the value shown in a circuit in the datasheet. I'm not sure if this will have any effect.
     
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