Calculating output voltage

Discussion in 'General Electronics Chat' started by Weras Asdsdw, Feb 14, 2016.

  1. Weras Asdsdw

    Thread Starter New Member

    Feb 14, 2016
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    Can someone tell me what is output voltage for this scheme?
     
  2. dl324

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    Mar 30, 2015
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    Welcome to AAC!

    Is this homework? Is the voltage AC?
     
  3. Weras Asdsdw

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    Feb 14, 2016
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    Yeah the voltage is AC
     
  4. dl324

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    Is this homework?
     
  5. Weras Asdsdw

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    Feb 14, 2016
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    Kind of... :)
     
  6. dl324

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    What do you think the output will be?

    Are you actually building this circuit?
     
  7. AnalogKid

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    Aug 1, 2013
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    The output is a half-wave rectified sinewave. Beyond that, your question needs a lot more work.

    If you are asking what the output voltage will be if measured with a digital voltmeter, it depends entirely on the load. It has a peak value, an average value, an RMS value, and an incorrect DC value on a meter - and all four of these are different numbers. If the load is a resistor, then the 1 M resistor in your drawing is one part of a voltage divider. If the load is a capacitor, then the size determines what will appear on a meter.

    ak
     
  8. Weras Asdsdw

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    Feb 14, 2016
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    No this is part of bigger scheme, I think it should be around 5V
     
  9. dl324

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    What is the voltage drop of a diode? What will it do on the negative half cycle of the input?
     
  10. Weras Asdsdw

    Thread Starter New Member

    Feb 14, 2016
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    The output voltage should activate the optocoupler
    The measured voltage output was 0.5V but the optocoupler didn't activate, so I think it should be around 5V for it to work
     
    Last edited: Feb 14, 2016
  11. dl324

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    How are you coming up with 5V for the output?

    You said this was "sort of" homework. Is it or isn't it?
     
  12. Weras Asdsdw

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    Feb 14, 2016
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    Its not homework
     
  13. dl324

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    Then as AK said, the output will be a half wave rectified sinewave and the voltage won't be 5V (DC or AC). You need to add reverse polarity protection for the opto LED.
     
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  14. Weras Asdsdw

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    Feb 14, 2016
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    Thank you for answer
     
  15. dl324

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    You're welcome.

    To protect the opto LED, you can install the existing discrete diode anti-parallel to the LED.
     
  16. roger finder

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    Nov 3, 2015
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    half wave rectifier voltage - diode drop voltage
     
  17. hp1729

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    Nov 23, 2015
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    Not enough current to turn on the optocoupler?
    Self-assigned homework? If it is assigned homework you will get guidance, not answers.
     
  18. hp1729

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    Nov 23, 2015
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    To get the 20 mA or so the optocoupler needs you need about 11,000 ohms, but that would mean you have to be a 10 Watt resistor. The voltage across the LED sets itself. (Maybe 1.2 V?) And yes, use a protection diode.
     
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