a bit of help required

Discussion in 'The Projects Forum' started by naughtyisha, Mar 18, 2009.

  1. naughtyisha

    Thread Starter New Member

    Mar 18, 2009
    3
    0
    hi people.... well m having a problem designing a power supply m building a +-15v supply.... n m not getting the proper output wat i m getin is +6.5 and -7.5 m presently using a transformer of 12-0-12 do i need to use a transformer of higher rating like 20-0-20..... m unable to get wat the problem is ... can anyone help????
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Why don't you post a schematic of what you have so far?
     
  3. naughtyisha

    Thread Starter New Member

    Mar 18, 2009
    3
    0
    ohkies.... heres from whr i got the circuit... and here the transformer rating is 12-0-12..... but not getting the desired output..... and further i have to use this supply for a first order high pass filter.. which involves use of opamp.... so help me out heres giving the schematic....
    [​IMG]
     
  4. naughtyisha

    Thread Starter New Member

    Mar 18, 2009
    3
    0
    plz reply asap
     
  5. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    The filtered output from the transformer is just barely able to source the regulators under ideal conditions. This is a very "optimistic" circuit. If your line voltage is low, then the transformer output will be too low - which sounds like your problem.

    What voltages are on the 2200 uF capacitors? If it's under 16.8, the regulators won't work.

    The fastest and least expensive fix would be to substitute 7812 and 7912 regulators. Most analog circuits can operate with lower voltages.
     
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