556 Divider Multiplier Help

Discussion in 'The Projects Forum' started by apprenticemart2, Jun 26, 2014.

  1. apprenticemart2

    Thread Starter Member

    May 7, 2013
    67
    7
    Hi,

    I'm trying to build this 556 voltage divider/doubler/inverter but I can't get it to work.

    In the photograph, ignoring the 1000pF surface mount ceramic cap I count 5 ceramic caps and 5 electrolytics, but the schematic shows 6 electrolytics.

    I think there may be a mistake in the schematic and I'm struggling to see enough detail in the photo to work out which cap may be wrong.

    Maybe to the professionals something sticks out like a sore thumb?

    Cheers
    Martin
     
    Last edited: Jun 26, 2014
  2. apprenticemart2

    Thread Starter Member

    May 7, 2013
    67
    7
    EDIT:

    I think that the problem might be with one of the 47uF capacitors from pin 5 on the -5V line or the 4148?

    Basically I need a circuit that will give me +10V and -5V from a +5V supply. This circuit is measuring +11.8V and -4.38 so it's more likely there's something wrong with the 10v side.
     
    Last edited: Jun 26, 2014
  3. apprenticemart2

    Thread Starter Member

    May 7, 2013
    67
    7
    OK. I think the odd one out is the ceramic capacitor near Pin 2 of the 556.

    In the schematic I think this cap is shown as a 47uF electro and it maybe should be a 0.047uF ceramic (or a different value?)

    It's the cap second from right that goes to a 4148 from 0V?
     
  4. alfacliff

    Well-Known Member

    Dec 13, 2013
    2,449
    428
    how can you expect precision from an unregulated supply? the output will vary with load.
     
  5. bertus

    Administrator

    Apr 5, 2008
    15,649
    2,348
    Hello,

    Did you connect pin 7 of the NE556?
    This should be the ground pin.
    (I do not see it in your schematic).

    [​IMG]

    Bertus
     
  6. apprenticemart2

    Thread Starter Member

    May 7, 2013
    67
    7
    Hi,

    The load is a 4116 RAM chip.
     
  7. apprenticemart2

    Thread Starter Member

    May 7, 2013
    67
    7
    Yes. I have this outputting a voltage but I think the -5V may be too low. The +10V output actually measures 12v under load which is normal for a 4116.

    I just can't work out why one of the electrolytics in the schematic has become a ceramic in the picture.

    Thanks for your suggestion.

     
  8. apprenticemart2

    Thread Starter Member

    May 7, 2013
    67
    7
    OK. I might do this a different way using 2 x ADM660 or something.
    Thanks everyone.
     
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