12v car starter

Discussion in 'General Electronics Chat' started by brent_1979, Nov 29, 2007.

  1. brent_1979

    Thread Starter New Member

    Nov 29, 2007
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    I need to reduce the speed of the starter and was wondering if anyone knew how to do this. Would a rheostat work?
     
  2. thingmaker3

    Retired Moderator

    May 16, 2005
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    A pulse width modulator (PWM) would work better. You can use the search function (in the blue bar up top) to find lots of information on PWM.
     
  3. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    When under load (starting an engine), starters draw hundreds of amps. Definitely not a candidate for a rheostat.
     
  4. brent_1979

    Thread Starter New Member

    Nov 29, 2007
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    I am using it to wind up a spool for cable and it winds up way to fast thats why I need to slow it down
     
  5. brent_1979

    Thread Starter New Member

    Nov 29, 2007
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    What is the most economical way and will the starter burn out any sooner from being slowed down also
     
  6. thingmaker3

    Retired Moderator

    May 16, 2005
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    PWM is very economical. Won't hurt the motor, either.

    When motors burn out from running too slowly, its because of mechanical loading. If you'd like details on why, I can provide some links.
     
  7. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    Do You know how much current the motor draws when you are winding up the spool? You may need some hefty MOSFETs or IGBTs to PWM a starter motor.
     
  8. beenthere

    Retired Moderator

    Apr 20, 2004
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    You may have a hard time with the project. Car starters are series wound for max power, and may not be very controllable, even with PWM. I wonder is a VSR drill wouldn't do better.
     
  9. neorules

    Member

    Nov 30, 2007
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    I often use hacked $15 power tools for drive motors on robots I build... The built in gear box helps... Starter motors have lots of power but aren't designed to run very long... They are high current high heat devices... Most PWM controllers would pop when you first use the starter. (back EMF).

    most winches that are used to pull things (car boat) use a smaller motor with a worm gear reduction or a complex planetary gearbox.

    What is the pull you need?
    check banebots on the web.. they make small gear motors that are just like the guts of bigger powerdrill / screwdrivers but are generally less expensive.
    JC
     
  10. thingmaker3

    Retired Moderator

    May 16, 2005
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    Wow. Even with snubber diodes?
     
  11. neorules

    Member

    Nov 30, 2007
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    The only way to tell is to try....
    The back EMF and of course the noise a starter makes I think would toast even the stronger esc's.... Unless you have soft start and current limiting as well as ramp down on the stopping....
    The arc you get hooking up the cables to the battery from the starter isn't anything compared to the arc I got when I took the batter cable off... LOL...
    scared the pooooo out of me...
    A lot of guys have tried to use them in robotic combat and often tried to use a solenoid instead only to have them arc weld their contacts after a while of running....
    Plus the heat.. I don't think the standard wound starter likes to run more than a few minutes at best.....

    But then again I do have some nicer 300 amp speed controllers...
    Hmmmmmm... do I "smell" an experiment...

    But that is just my oppinion... Hopefully somebody else will chime in here....
    JC
     
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