Help on a few questions.

Discussion in 'Homework Help' started by Court, Jul 30, 2014.

  1. Court

    Thread Starter New Member

    Jul 30, 2014
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    I have an important job interview and they will be quizzing me on these questions. I have a degree in electronics but its been years since I have done this. I have a great opportunity and need a little help. Any and all help is appreciated. There are 10 questions that I could be asked. I have attached them. 001.jpg.jpg

    002.jpg.jpg

    View attachment 71303
     
    Last edited: Jul 30, 2014
  2. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    Did someone finally turn off google?
     
  3. Court

    Thread Starter New Member

    Jul 30, 2014
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    I am looking for some real time help. I have googled a few things. I thought maybe I could get some better understanding than reading through pages and pages.
     
  4. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    The last page is up side down.
     
  5. tshuck

    Well-Known Member

    Oct 18, 2012
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    Which, in particular, do you need help with?
     
  6. Court

    Thread Starter New Member

    Jul 30, 2014
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    Right side up now!
     
  7. Court

    Thread Starter New Member

    Jul 30, 2014
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    I mainly need help with the schematics. I have an idea of the output for the op amp. The solenoid driver I have really no idea. I have been going through my old school books and can't find anything about it.
     
  8. tshuck

    Well-Known Member

    Oct 18, 2012
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    Question 8 seems a bit unclear, but, you can at least get the input voltage required for a 50% duty cycle using linear interpolation on the two points you are given.

    Use: y – y1 = m(x – x1), where (x,y) and (x1,y1) are your given data points.
     
  9. Court

    Thread Starter New Member

    Jul 30, 2014
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    Really you lost me.
     
  10. shteii01

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    Feb 19, 2010
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    Read the schematic note.

    When voltage at Pin 3 is 3 volts, duty cycle is 30%.
    When voltage at Pin 3 is 2.6 volts, the duty cycle is 40%.
    So.
    A reduction of voltage at Pin 3 by 0.4 volts produced an increase in duty cycle by 10%.
    You need duty cycle of 50%. To me it seems that if I reduced the voltage at Pin 3 by another 0.4 volts, I would gain another 10% in the duty cycle. So. When voltage at Pin 3 is 2.2 volts, the duty cycle will be 50%. That is why they stuck the adjustable resistor at Pin 3, so that you can decrease the the voltage drop at Pin 3 and increase the duty cycle.
    And.
    Based on the two points that the note provided, you can derive the linear relationship between the voltage drop at Pin 3 and the length of the duty cycle.
    y=mx+b
    Duty Cycle=m*Pin 3 voltage+b
    30%=m*3+b
    40%=m*2.6+b
    Can you do this middle school math and find slope m and y intercept b?
     
  11. Court

    Thread Starter New Member

    Jul 30, 2014
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    Yes thank you. I guess I need glasses.
     
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