12V DC supply using 9V battery

Discussion in 'The Projects Forum' started by rockerpaluza, Sep 7, 2010.

  1. rockerpaluza

    Thread Starter New Member

    Sep 7, 2010
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    Hye all..i am new in this forum..
    Currently im working on EOG amplifier project, which deals with biopotential from human..i'm so afraid to use the power supply from the wall socket to my amplifier,because it may cause electrical hazard to my test subject..so i guess it will be better if i use 9V battery..however, i want to supply 12VDC to my amplifier..How do i achieve this?
     
  2. Dyslexicbloke

    Active Member

    Sep 4, 2010
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    The first obvious suggestion is a 12V battery ... did I miss something
    or
    Two 9V batteries and a voltage regulator,
    or
    Some sort of boost converter, which is probably overkill.
    How much current do you need and for how long.?
     
  3. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Have you considered using multiple AA or AAA batteries in a holder?

    You might consider using a efw CR123A batteries in series.

    You could use a boost converter to get 12v, but your battery life would be considerably reduced.
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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  5. rockerpaluza

    Thread Starter New Member

    Sep 7, 2010
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    thanks for the replies.i think i will use 2x9V batteries plus voltage regulator..but i have another question..i need to supply power to INA126P IC..this IC have +12V terminal,-12V terminal,and GND terminal..will the power supply circuit as in the attachment works? Can i make such connection to the IC??
    thanks..
     
  6. gerty

    AAC Fanatic!

    Aug 30, 2007
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    the 7812 will work (you are missing some capacitors) but the 7912 will not work. You need a power supply the will have 24v between the +12 and -12.
    You cannot connect a negative voltage regulator (7912) to a positive line and get a negative voltage from it.
    You would need 2 12v batteries in series to get your +12 and -12 with the center point of the 2 batteries being ground.
     
    Last edited: Sep 8, 2010
  7. t06afre

    AAC Fanatic!

    May 11, 2009
    5,939
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    Hi Rockerpaluza you should forgett your circuit as it is very wrong. With 2 volt batteries you may create +/- 9 volt. Or +18 volt. But creating -12 volt from +18 volt like you try to do will never ever work. Also you should know what a 9 volt do not have very much capacity. So I would recommend a medical grade power supply. A component I have often used is the THI series from Traco Power http://www.tracopower.com/Reinforced-I-O-Isolation.211.0.html
     
  8. gerty

    AAC Fanatic!

    Aug 30, 2007
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    Here's a crude drawing


    edit: just realized it's for medical use, stick with medical grade equipment.
     
    Last edited: Sep 8, 2010
  9. rockerpaluza

    Thread Starter New Member

    Sep 7, 2010
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    oww..so i was wrong..i'll check on the THI series afterward..thanks
     
  10. marshallf3

    Well-Known Member

    Jul 26, 2010
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    They make small converters that will take 9V and give you +12V and - 12V out. I think I saw some premade as modules on Mouser a month or so ago.

    Actually you've got your choice of 3.3V, 5V or 12V in for these examples but there are others:
    http://www.mouser.com/catalog/catalogUSD/642/2043.pdf

    A 3.3V one would be a good choice as they work down to 3V and most of those large lithium coin cells put out between 3 - 3.3V and would probably last as long if not longer than a 9V battery to begin with.
     
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