Relaxation oscillator Noob need education

Discussion in 'The Projects Forum' started by theSwede, Jan 26, 2013.

  1. theSwede

    Thread Starter New Member

    Jan 26, 2013
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    Don´t laught please :) need some help about my project what i basically want is a solenoid "electromagnet" That switch its magnetic flux in a Oscillation fashion. Much like a speaker my solenoid is about 1.5 ohm. And to get the oscillation i research about relaxation oscillator and transistor oscillator but i went for the Rel for the of easy build. But i am very noob and i cant get it to work. The pic below show schematic and how i assemble it

    Probably i am so noob that my theory is not valid. I want to have the output voltage the same as i take in in order to get stronger or softer magnetic field but i only get 0.04 mv at the output i have an pot to regulate the freq the voltage do increase or decrease in the output some but do not oscillate i think.. i thing i destroyed the ic or i connected it wrong. or it is the wrong circuit all together? hope i have explained my self clear sorry otherwise!

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  2. tracecom

    AAC Fanatic!

    Apr 16, 2010
    3,871
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    Assuming that the op-amp is an LM741 or equivalent:

    What is the power voltage and source?

    The cap looks very big for 1 μF; is that what it is? Do you have the polarity correct?

    What is the value of the pot? Try removing it and using the 10k fixed resistor to see if it oscillates.
     
  3. theSwede

    Thread Starter New Member

    Jan 26, 2013
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    Hello yes it is a lm741.. and yea i tried switching from a 1 uf to a 10 uf that one is in the pic. Tried a fixed resistor to.. 10k

    damn i suck at this
     
  4. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    Are you using a dual voltage power supply? LM741's need a + supply, a - supply, and a ground. A couple of 9V batteries can be configured to work.
     
  5. eblc1388

    Senior Member

    Nov 28, 2008
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    Adds the extra resistor as indicated or else your oscillator won't oscillate.

    [​IMG]
     
  6. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    With a dual voltage power supply, the OP's original circuit produces a nice square wave at about 44 Hz.
     
  7. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    Here is a schematic showing the batteries that make up the dual voltage power supply.

    [​IMG]
     
  8. eblc1388

    Senior Member

    Nov 28, 2008
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    The following circuit works with a single 9V supply.

    [​IMG]
    [​IMG]
     
    Last edited: Jan 27, 2013
    tracecom likes this.
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