NE566N Voltage Controlled Oscillator Problem

Discussion in 'General Electronics Chat' started by Tony Elliott, Dec 26, 2015.

  1. Tony Elliott

    Thread Starter Member

    May 8, 2015
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    Hello All About Circuits,

    I have made the attached schematic and have no sound of oscilloscope signal from the NE566N. I have tried three different chips from different distributors to test if I have a bad chip and still no luck. I have powered from a dual power supply at 15v with ground (seen in attached photo) as instructed on the schematic. The only thing I can think is the power supply is set up wrong? I have it set on automatic current and the schematic book says current drain is around 10mA. Can somebody please tell me what I am doing wrong???
    IMG_1644.JPG IMG_1647.JPG IMG_1648.JPG FullSizeRender-4.jpg
     
  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Well, you've shown the IC and description, but not the schematic of you're actual circuit. Unfortunately, a view of the breadboard layout isn't very helpful.
     
  3. Tony Elliott

    Thread Starter Member

    May 8, 2015
    140
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    The second image is the schematic.
     
  4. Tony Elliott

    Thread Starter Member

    May 8, 2015
    140
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    Here is a better view of the bread board.
     
  5. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    And the crossed out parts are missing? Or is it the actual schematic?
     
  6. tindel

    Active Member

    Sep 16, 2012
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    Doesn't look like your op-amp is powered. or decoupled.

    [edit] if you're using a 741 maybe you do have it powered
     
    Last edited: Dec 26, 2015
  7. tindel

    Active Member

    Sep 16, 2012
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    If I make a few assumptions of where your power rails are, It looks like the circuit is right... decouple the opamp... and also make sure that your scope is scaled properly. Other possibility is to make sure that the trim pot is linear.
     
  8. Tony Elliott

    Thread Starter Member

    May 8, 2015
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    The crossed out parts are when I was making the circuit. The op amps are all powered The pot is a B 100k.
     
  9. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Have you checked that the voltages on the power supply pins of both ICs are what they should be?
     
  10. Tony Elliott

    Thread Starter Member

    May 8, 2015
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    I have powered the LM741 using the same rails as the NE566N, I could try using a separate power rails. the max for the LM741 is +-22v
     
  11. sailorjoe

    Member

    Jun 4, 2013
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    Tony, when things aren't working it's time to forget about what you think you did, and figure out what you actually did. You powered the LM741 and the 566 from the same rails. Did you use a voltmeter or o'scope to prove that the hookup is correct? Did you measure right at the chip pins? Please don't guess....make a measurement.

    Also, did you notice that the 566 has negative 15 Volts (-15V) connected to its pins, not +15V. That's unusual and something that could be missed.

    And by the way, increasing the power voltages to +/-22V won't make it work if it doesn't work at +/-15V. 15 is more than enough.

    Next step, measure the voltage coming out of the 741. Does it vary when you move the pot? How much does it change? Is it what you expect it to do?

    If that works, put your scope on pin 7, the charging capacitor. Is there a signal there? It should look like a triangle wave.

    Let us know how that goes, please.
     
    Last edited: Dec 27, 2015
  12. Tony Elliott

    Thread Starter Member

    May 8, 2015
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    Thank you for your message, I'm going back to my studio this afternoon and try out your advice:) in the meantime I found this video it's how to setup a -12 +12. I have setup a 0 to + voltage on my circuit not a - + supply.
     
  13. atferrari

    AAC Fanatic!

    Jan 6, 2004
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    Based on a personal experience well deep in my past, I would stop looking for the reason and take all. parts and wires out. Then I would rework the connections, inserting all ICs first, then connecting ALL commons, then ALL positive supply voltages, then ALL negatives and finally taking one IC to connect each pin in numerical sequence and then next IC, completing the last.

    I use short wires so tracing actual connection is easier. The very first test is ALWAYS that all commons are common to the PSU. Then I check the other voltages and then signals.

    If not the above, check that your common is everywhere where it should.
     
    Tony Elliott likes this.
  14. Tony Elliott

    Thread Starter Member

    May 8, 2015
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    The circuit is now working I have been calibrating it today. Many thanks for all you advice. It was the power, I used my dual power supply, two in series to create a -15v, ground and +15v. :)

    1913943_10153106208155882_5179638587769999871_n.jpg 481188_10153106208120882_8958157871790483633_n.jpg 735057_10153106367230882_7203887428651109740_n.jpg 1935488_10153106367225882_7337944241668128033_n.jpg
     
  15. atferrari

    AAC Fanatic!

    Jan 6, 2004
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    Nice feeling when things start to run as expected. Congratulations!
     
    Tony Elliott likes this.
  16. Tony Elliott

    Thread Starter Member

    May 8, 2015
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    Got there in the end:)
     
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