Connect with us

convert 12V down to 9V DC

Discussion in 'Electronic Basics' started by [email protected], Oct 3, 2008.

Scroll to continue with content
  1. Guest

    My kids' electric scooter has a 6V motor and battery. The 6V battery
    doesn't give enough juice, but a 12V battery I installed gives too
    much juice (wheels skidding when the pedal is pressed, etc).

    The "Gas" pedal is a simple on/off switch.

    I'd like to provide 9VDC, at about 5A (a guess - I haven't measured
    the current yet - that will take some doing, to determine the startup
    surge current with a kid sitting on it).

    I was thinking LM317 with pass transistor (I've got a spare 2N3055),
    but I'm wondering if I can simplify this schematic a bit (under High
    Current Regulated Supply):
    http://ourworld.compuserve.com/homepages/Bill_Bowden/page12.htm

    Why a 2N3904, why so many resistors? Can they be omitted?

    I was also thinking of a buck converter, but I have no P-channel
    mosfets.
    http://www.daycounter.com/LabBook/BuckConverter/Buck-Converter-Equations.phtml

    Thanks,

    Michael
     
  2. Jamie

    Jamie Guest

    Just put some large diodes in series, each will give you a ~ 0.6 volt drop./
    The simplest method I can think of.


    http://webpages.charter.net/jamie_5"
     
  3. Tom Biasi

    Tom Biasi Guest

    Controlling large currents like that is always a PITA.
    For cars and scooters I usually make a "shifter" by tapping batteries at 3,
    6 , 9, and 12.

    Tom
     
  4. Guest



    Update - surge current is around 15-20 A actually with the 12V
    battery. A linear regulator might not be such a great idea after
    all...

    Michael
     
  5. Guest


    Interesting; I'll look into that...

    Thanks; I'll look into that. I have a slightly (physically) bigger 6V
    battery that I'll try. (None of them spec their surge current
    capacity, only A-hr capacity... more research needed...)

    Yep, heat... I guess I could be safer by using 20 3V, 1A light bulbs
    to allow 20 A to pass, but then that wouldn't be exactly cheap
    either...


    Yep, especially for 20A...

    Thanks,

    Michael
     
  6. neon

    neon

    1,325
    0
    Oct 21, 2006
    Motors like batteries don't care about volts . use an lm117 as a current regulator with the 2n 3055 pass then just vary the current easy enough.
     
  7. Guest

    ....zap...

    That did it! A fatter 6V battery does the trick.

    Thanks,

    Michael
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-