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12134Re: [SeattleRobotics] current limit?

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  • Mark Medonis
    Nov 1, 2002
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      Well, you have a couple of options. You can add a 1.4 ohm resistor in
      series, giving you 2.4 ohms total. Ohm's law says V = I * R, so 12V / 5A =
      2.4 ohms.

      Or, you could use a bipolar resistor and a VERY big heat sink, adjust the
      base voltage to get the current level you want. The transistor acts like a
      variable resistance in that case, although you can set it to a particular
      current level independent of supply voltage.

      A FET can do this trick as well.

      Now, if your load was inductive, you could use PWM to control the current.
      This is the most efficient method by far. But for a purely resistive load,
      it doesn't really work. You would get 12A, then 0, then 12A, then 0.

      Mark Medonis


      > From: "toolguy500" <toolguy500@...>
      > Date: Fri, 01 Nov 2002 20:43:04 -0000
      > To: SeattleRobotics@yahoogroups.com
      > Subject: [SeattleRobotics] current limit?
      >
      > yall,
      >
      > what do i do to limit current in a circuit?
      >
      > i have about a 12v source i wanna connect to about a 1 ohm load,
      > limit to about 5A and have the supply stay around 12v.
      >
      > suggestions?
      >
      > thanx,
      >
      > jim
      >
      >
      >
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