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    7Amp Heater and PWM using MOSFET

    Hello everyone,

    I'm working on a project that controls 12Vdc 7Amp silicon heater pad using MOSFET.
    I tried HA210N06 MOSFET with a heatsink but it doesn't work correctly, the heater doesn't get hot but the MOSFET is getting very hot, I tried another lower amper heater it's work but also not get very hot with a 100% duty cycle as I connect it directly to the power supply.

    I'm using dual output power supply 5v for microcontroller and 12v 15A for the heater.
    PWM frequency is 500hz.
    I'm using pic 18f4685 and programming with MikroC.

    The circuit is attached.

    my question is this MOSFET could work correctly but I have some connections problem or coding problem?

    Thank you.

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    Re: 7Amp Heater and PWM using MOSFET

    Hi,

    If HA210N06 is getting hot, then you didn't drive it correctly.
    It should not even need a heatsink when driven correctly.

    Sadly your schematic does not show how you drive the gate...thus we can not validate it.

    Did you read the Mosfet datasheet?

    Klaus
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    Re: 7Amp Heater and PWM using MOSFET

    If you will mix up drain and source, all current will pass throuhg the internal diode and thus it can warm up also
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    Re: 7Amp Heater and PWM using MOSFET

    Quote Originally Posted by KlausST View Post
    Hi,

    If HA210N06 is getting hot, then you didn't drive it correctly.
    It should not even need a heatsink when driven correctly.

    Sadly your schematic does not show how you drive the gate...thus we can not validate it.

    Did you read the Mosfet datasheet?

    Klaus
    Thanks Klaus,
    I think the problem is VGS in HA210N06 is 10V so it will never work with pic microcontroller. i just realized that.
    but i still need help for chossing the best one for this application.

    the gate is coneccted with RC2/CCP1 PIC 18F4685



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    Re: 7Amp Heater and PWM using MOSFET

    Quote Originally Posted by Easyrider83 View Post
    If you will mix up drain and source, all current will pass throuhg the internal diode and thus it can warm up also
    did you mean mix the ground? or what ?



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    Re: 7Amp Heater and PWM using MOSFET

    Hi,

    Two options:
    * use a Mosfet working with low V_gs, also called "logic level Mosfet"
    * or use a gate driver that is able to drive 10V gate voltage

    Klaus
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    Re: 7Amp Heater and PWM using MOSFET

    .... or add a small NPN bipolar transistor as a MOSFET driver. Emitter to ground, drive the base from the PIC through a suitable current limiting resistor (~100 Ohms) and connect it's collector to the gate of the MOSFET. Also add a pull-up resistor (~470 Ohms) to the collector/gate junction to 12V. That should let the bipolar transistor saturate when the PWM signal is high, taking the gate to near zero volts and let the gate go to 12V when the PWM signal is low. It is only two more components but it lets you keep the existing MOSFET.

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    Re: 7Amp Heater and PWM using MOSFET

    Quote Originally Posted by KlausST View Post
    Hi,

    Two options:
    * use a Mosfet working with low V_gs, also called "logic level Mosfet"
    * or use a gate driver that is able to drive 10V gate voltage

    Klaus
    I think it is easier to change the MOSFET to a Logic level MOSFET, but can you please recommend me one..
    this heater will work 24 hours with PWM and PID system so I need a good MOSFET.

    - - - Updated - - -

    Quote Originally Posted by betwixt View Post
    .... or add a small NPN bipolar transistor as a MOSFET driver. Emitter to ground, drive the base from the PIC through a suitable current limiting resistor (~100 Ohms) and connect it's collector to the gate of the MOSFET. Also add a pull-up resistor (~470 Ohms) to the collector/gate junction to 12V. That should let the bipolar transistor saturate when the PWM signal is high, taking the gate to near zero volts and let the gate go to 12V when the PWM signal is low. It is only two more components but it lets you keep the existing MOSFET.

    Brian.
    Thank you Brian.
    I'll try this and give you the feedback.



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    Re: 7Amp Heater and PWM using MOSFET

    Hi,

    I can not recommend one...
    If I wanted to find a suitable Mosfet, then I'd use online selection tools of semiconductor manufacturers or distributors.

    Klaus
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    Re: 7Amp Heater and PWM using MOSFET

    just google logic level or look at element 14 website



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    Re: 7Amp Heater and PWM using MOSFET

    IRLZ24, IRLZ44
    These are logic level MOSFETs
    I use these for LED lighting regulation, my main working light is approx 75W which at 100% duty gives ~6,2A :)
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