Peltier beer / soda cooler circuit... mmmmm, beer

Discussion in 'The Projects Forum' started by villacherman, Jun 4, 2009.

  1. villacherman

    Thread Starter New Member

    May 11, 2009
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  2. bertus

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  3. beenthere

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    Apr 20, 2004
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    No, it will not turn on with 5 volts applied. You need a logic-level FET like the IRL520 - http://www.hobbyengineering.com/H1586.html

    These FET's will turn on with +5 applied - note that a TTL level is perhaps 3.8 volts, so a CMOS gate is best to drive the device.
     
  4. villacherman

    Thread Starter New Member

    May 11, 2009
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    beenthere - thanks for the info, I think that is exactly what I need...

    I'm assuming PWM to the MOSFET is better than driving it with a particular voltage?
     
  5. bertus

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    Hello,

    PWM is more efficient than linear.
    PWM can be made "manual" (with opamps) or by an microcontroller.
    Linear would make the mosfet very hot.

    Greetings,
    Bertus
     
  6. villacherman

    Thread Starter New Member

    May 11, 2009
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    Bertus -

    A couple of questions:

    1. by "manual", do you mean analog? I currently use an opamp between the microncontroller and the MOSFET. I think this is changing the PWM signal from the microcontroller into a linear voltage. I am generating a LOT of heat.

    2. I could run the MOSFET straight from the microcontroller with PWM (picaxe). But I was told that:

    "One note, there is capacitance in the gate of the FET that must be considered in the PWM drive signal. Therefore if the FET is being driven at a high frequency, a low impedance circuit must be used to turn the FET on and off rapidly to minimize the time that the FET is in the transition region between being fully on and fully off"

    Can this be considered a decent low impedance circuit to get this rapid on/off?

    http://sites.google.com/site/elektrogeekproject/circuit1
     
  7. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    You need to remove the 0.1μF capacitor at the gate.
    Put a resistor of 220 Ohms between the output of the microcontroller and the gate of the mosfet.

    Greetings,
    Bertus
     
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