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Controlling power mosfet

Discussion in 'General Electronics Discussion' started by 3eprabu, Aug 12, 2015.

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  1. 3eprabu

    3eprabu

    5
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    Aug 12, 2015
    Guys need some help here . Im using a irf830 power mosfet to control a dc light , but for some reason i can't control the mosfet via the gate . The light turns on automatically without even supplying signal to the gate . I connected the source terminal to the negative of the battery , one side of the light is connected to the battery and the other is connected to the drain of the mosfet . I tried the same connection using a transistor and it worked fine . totally confused . need some help PLZ . I have tested the mosfet using a multimeter and its working fine .
     
  2. Gryd3

    Gryd3

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    Jun 25, 2014
    Please link the part# and a diagram to confirm which pins you are using.
     
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  3. Martaine2005

    Martaine2005

    2,745
    739
    May 12, 2015
    Here is the Datasheet.

    EDIT: Look at the internal workings of the mosfet.

    Martin
     
    Last edited: Aug 12, 2015
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  4. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    You may need a pull down resistor on the gate to discharge the internal gate capacitor. Show us a circuit diagram.
    Thanks
    Adam
     
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  5. 3eprabu

    3eprabu

    5
    1
    Aug 12, 2015
    Thanks Adam , I added a pull down resister and its working fine .

    My question now is , will this pull down resistor effect the PWM signal I'm going to supply to the gate ? I'm planning to build a light dimmer with the mosfet .

    Thanks in advance .
     
  6. 3eprabu

    3eprabu

    5
    1
    Aug 12, 2015
    Thanks, your help is very much appreciated. :). I'm able to controll the mosfet now
     
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  7. 3eprabu

    3eprabu

    5
    1
    Aug 12, 2015
    Thanks, your help is very much appreciated. :). I'm able to controll the mosfet now
     
  8. BobK

    BobK

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    Jan 5, 2010
    The resistor can probably be 100K or even 1Meg, and at that level It will not affect the PWM signal.

    Bob
     
  9. 3eprabu

    3eprabu

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    Aug 12, 2015
    Thanks bob . Any idea how to step down 240 v DC to 10 v DC ?
     
  10. BobK

    BobK

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    Jan 5, 2010
    I wouldn't. Do you have another source of power?

    Bob
     
  11. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    As Bob kindly chipped in with the answer I agree with Bob.
    Adam
     
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