Mosfet switching help needed...!!!

Discussion in 'Embedded Systems and Microcontrollers' started by bhargav shankhalpara, Feb 15, 2014.

  1. bhargav shankhalpara

    Thread Starter Member

    May 9, 2010
    Hello Everyone...

    I decide to make automatic cradle for baby's, for that i use magnet attraction and repulsion property. for that i attech 2 powerful magnet on movable pipe of cradle and put one coil near this magnet.

    Now to obtain movement we need to energy's coil such a way that moment of cradle can be obtain.

    for that i directly connect two terminal of coil with 12V DC power supply and make switching with hand. Current Rating was 2.5A when turn on. This way i obtain movement in one direction. as i increase coil voltage large movement can be obtain.

    after that i decide to switching it with micro-controller so i can obtain movement in both direction by changing current flow direction. for that i use H-BRIDGE concept.

    i make h-bridge using Relay but it make noise as TICK TACK.
    To Avoid this problem i use power mosfet 55NF06.

    Circuit diagram is attached with this post...

    Problem with mosfet is, after starting circuit mosfet start heating and after minute it become fry.

    please help me, what should i do to avoid this kind of problem....?

    Thank you..!!

    Bhargav Shankhalpara India.
  2. bertus


    Apr 5, 2008

    The mosfets can not be driven directly from the MCU.
    The gate voltages will be to low for the bottom fets and not go above the VCC line for the upper fets.
    The gate voltages will need to be 10 Volts above the source voltages.
    You will need a mosfet h-bridge driver to work with these fets.
    Intersil has this one for the purpose:

    I also have attached the datasheet of your fet and a PDF of a study on a H-bridge driver.

  3. Brownout

    Well-Known Member

    Jan 10, 2012
    You'd be better off using a geared motor and an offset shaft. Your idea using magents is a good one, but not very practical.