variable DC power supply

Discussion in 'The Projects Forum' started by InnocentOfTheWorld, Dec 18, 2010.

  1. InnocentOfTheWorld

    Thread Starter Member

    Apr 15, 2010
    I've to submit this project in my university:

    A Variable DC Power Supply with following features:
    (a) Split 1.2 to 17 volts (both negative and positive polarity), capable
    of supplying 800mA.
    (b) Constant output of 5, 9, and -9 volts, capable of supplying 1A.

    Question 1
    What transformer should I go for ... ? Center-tapped or plain ... ? With what electrical ratings ... ? Voltage/Current ... ?

    Question 2
    Should I use some kinda regulator ICs (e.g. LM317, L7809, etc.) or should I go for zener diodes or potential dividers ... ?

    Question 3
    What should be the value of filter capacitor ... ?

    :) :)

    P.S. I will have to choose my own desired load and line regulations. And I'll have to support my selection with reasons. Please tell me what should be the most suitable load/line regulations here, with reasons ... ?
  2. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    If you need both positive and negative voltage, which transformer do you THINK you need to use?

    Regulators are your friends when building power supplies.

    Filter capacitor values can be figured from the data sheets, and from experience in designing circuits. For power supplies, they function as smoothing filters, and the larger the value, the larger the initial INRUSH current is at power ON.

    Start by gathering lots and lots of datasheets on the components you are considering using.

    For the reasons, you should consult the class textbooks, as the teacher will expect you to 'know' the material presented in class.
  3. deanluna

    New Member

    Dec 11, 2010
    good quality zenors work well.,., I don't think you'd want to use pots, you'll have to 'dial' in the voltage you're looking for every time, unless you use 2 or 3 I suppose.
  4. Wendy


    Mar 24, 2008