simple current control circuit

Discussion in 'The Projects Forum' started by judehue, Apr 23, 2010.

  1. judehue

    Thread Starter New Member

    Apr 20, 2010
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    Does anyone have any ideas for a relatively simple circuit that could take 0-3.3v input and drive 0 to 1.5 Amps into a solenoid with current feedback
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    What's the resistance of the solenoid?
     
  3. judehue

    Thread Starter New Member

    Apr 20, 2010
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    The solenoid has a resistance of 5.5 ohms
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    See the attached.

    The curved line (green trace) shows the power dissipation in the MOSFET; it peaks when current through the load (your solenoid) is about 3/4A. You will need to use a heat sink on the MOSFET.
    The red trace is the input voltage (0v-3.3v)
    The blue trace is the current through the load (0A-1.5A)

    This is presuming that your supply is 9v; a minimum of 8.5v is required. If your supply voltage is higher, power dissipation in the MOSFET will be substantially higher.

    If you're going to use this in an automotive application, you'll need some way to provide clean power.
     
    Last edited: Apr 23, 2010
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  5. judehue

    Thread Starter New Member

    Apr 20, 2010
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    I was looking at doing the same thing with an IRFZ10 but I had the sense resistor on the drain side
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    You could use the same schematic with an IRFZ10.
    But, sense resistor goes between the source and ground. Otherwise, it gets to be a hassle to determine the current. Having Rsense connected right to ground makes it easy.

    One thing I omitted was a reverse-EMF protection diode across the load. You should include one. Even a 1N4004 would work. Connect cathode to V+, anode to the drain.
     
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