Amplifying power to motors

Discussion in 'General Electronics Chat' started by Wolfgang, Dec 29, 2014.

  1. Wolfgang

    Thread Starter New Member

    Dec 29, 2014
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    I have a 18 volt dc motor that is being supplied with 6 v or -6 volts. How would I amplify the 6v to 18 or in reverse -6 to -18 v using a 12 v battery as an additional power source.
     
  2. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
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    So, do you want to power an 18V motor from a 12V battery?

    How much current does your motor require?
     
  3. MaxHeadRoom

    Expert

    Jul 18, 2013
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    If using an additional 12v battery then just series them up for 18v?
    Max.
     
  4. Wolfgang

    Thread Starter New Member

    Dec 29, 2014
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    6+ 12 v is 18 v. I can't put them in series because when the motor goes in reverse the ground and source swap so the it would be -6 + 12 v only 6 volts and it would be in the wrong direction. When forward I get 6 volts want 18. When in reverse I get -6 want -18.
     
  5. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Connect your 12V battery in-series with your existing 6V supply. Now you have 18V. Since it seems you need to reverse the motor, use an 18V H-Bridge, with the motor connected across the sides of the bridge. Your positive logic inputs (presumably 5V) can be referenced to 0V...
     
  6. blocco a spirale

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    Jun 18, 2008
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    If connected in series isn't there a risk, if the battery becomes discharged, of it receiving a reverse charge from the 6V power-supply?
     
  7. Wolfgang

    Thread Starter New Member

    Dec 29, 2014
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    The 6 v supply alternates to -6. Its like an ac supply, but there is no fixed frequency.
     
  8. Wolfgang

    Thread Starter New Member

    Dec 29, 2014
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    the 6 v supply used to power the motor hence the 6 and-6 volts for direction. Now I need more power so I have to increase the voltage to 18 for forward and -18 for backwards. The 6/-6 v supply isn't a battary it is the power coming from a seperate chip that I can't modify.
     
  9. Alec_t

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    Sep 17, 2013
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    Can't you just buy an 18V supply? Probably cheaper (certainly simpler) than building a circuit to combine and reverse the two supplies you have.
     
  10. Wolfgang

    Thread Starter New Member

    Dec 29, 2014
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    But how to swap the polarity of the 18 v battery so the motor can go in reverse? I can build and solder a circuit but Im clueless as to the design for this.
     
  11. Alec_t

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    Sep 17, 2013
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    As Mike said (post #5), use an 18V H-bridge.
     
  12. tcmtech

    Well-Known Member

    Nov 4, 2013
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    A simple DPDT relay would work just fine for the power handling and reversing process.
     
  13. Wolfgang

    Thread Starter New Member

    Dec 29, 2014
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    Thanks. Would it be possible to build a circuit like it using transistors instead?
     
  14. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Google 'MOSFET H-bridge schematic'
     
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