Need some help controlling a coil

Discussion in 'The Projects Forum' started by ELECTRO1234, Oct 23, 2015.

  1. ELECTRO1234

    Thread Starter New Member

    Oct 23, 2015
    3
    0
    Hello all,

    I have been working on a project controlling a coil to attract a metal bal at high speed.
    I measure the speed of the ball in front of the coil and then decide how fast i want the ball to excelerate because the speed it need to have when it leaves the coil is about 10 m/s.
    I found out i have about 9 miliseconds to use the coil. So what i was thinking is ill use a MOSFET and a pwm signal in this way i can change the dutycycle and then control the coil like in the drawing.
    But i red on a site if i want this to work i need to switch high side and low side because else the coil still will be magnetic. now is my question: does somebody know what they mean and how does is work since i have not much experience with coils.

    Specs:
    PWM signal : 3.3v 10Khz
    Coil: 51v 16A


    Thank you in advance
    Naamloos123.jpg
     
  2. pwdixon

    Member

    Oct 11, 2012
    488
    56
    Are you trying to make a rail gun?
    If you are then there's probably websites for that but I would have thought there might be a forum rule against that kind of project.
     
  3. ELECTRO1234

    Thread Starter New Member

    Oct 23, 2015
    3
    0
    no its for my internship, it will become a closed system
     
  4. pwdixon

    Member

    Oct 11, 2012
    488
    56
    In any case it sounds very like a rail gun so perhaps a site about rail guns (and there must be many) might actually be helpful.
     
  5. ELECTRO1234

    Thread Starter New Member

    Oct 23, 2015
    3
    0
    yea i have looked for those site's , also coilgunsites but the problem is with a coilgun and railgun u dont want to control the coil u just want it to fire it as fast as possible
     
  6. pwdixon

    Member

    Oct 11, 2012
    488
    56
    That might be a matter of trial-and-error on pulse sizing for a given setup.
     
  7. ronv

    AAC Fanatic!

    Nov 12, 2008
    3,290
    1,255
    People are right. The diode will keep the current going in the coil for a while.
    You can reduce this time by allowing the voltage to rise higher than what the diode will allow. Think zener diode.
    But with a 64 Mh coil you can only get a current of about 6 amps in 9 ms. :(
     
  8. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,798
    1,103
    I think ronv means a 74mH coil. You wouldn't have house-room for a 64MH one :D.
     
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