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Homework Help: Need a little help on another question folks

  1. Jun 9, 2010 #1
    1. The problem statement, all variables and given/known data
    right ive got a transformer question but I have no clue on what equations it requires.
    the circuit. it has a 220 RMS voltage with a dual transformer with 240-0 : 6-0 6-0 written beneath. there is then a combination of 4 diodes and a capacitor of 470uF value. we then have a voltage regulator with reference voltage of 1.25 volts and two resistors, the top one being 130ohms and the bottom being 600 ohms. there is one more capacitor of 47uF and then an 100mA fuse

    [ b]2. Relevant equations[/b]
    this is why i need your help folks I cant seem to find the equations in the notes i have.

    3. The attempt at a solution
    im afraid i cant give you answers since I don't have equations. but im being brutaly honest i need the equations within 4 hours if im gonna get the question done in time.
  2. jcsd
  3. Jun 10, 2010 #2


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    Staff: Mentor

    Sounds like a standard transformer --> full wave bridge rectifier --> adjustable linear voltage regulator. Here's the LM317 datasheet to get you going:

    http://www.national.com/ds/LM/LM117.pdf [Broken]

    Last edited by a moderator: May 4, 2017
  4. Jun 14, 2010 #3
    thanks for the previous help. ive also recieved extra help from my tutor. however he isnt clear on a couple of the equations as well as me, namely Vripple and the Vref ( he knows it 1+, but doesnt know which way the resistors should be Either Rtop/Rbottom or the other way round. be great if anyone could help within the hour.

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