problem in operating a power relay with the help of microcontroller

Discussion in 'Embedded Systems and Microcontrollers' started by devmania, Aug 22, 2010.

  1. devmania

    Thread Starter New Member

    Aug 22, 2010
    17
    0
    Hi Everyone,

    I am here with a problem and i hope some one will help me out with this. I want to operate a power relay with the help of a microcontroller , the rating of the relay is 415v 12A . I have attached some files regarding the details of the relay i am going to use. Please suggest me what to do ?

    Regards
    Dev
     
  2. devmania

    Thread Starter New Member

    Aug 22, 2010
    17
    0
    Is it the same way how we control the 12v relay or the set up is different .
     
  3. debjit625

    Well-Known Member

    Apr 17, 2010
    790
    186
    In allaboutcircuit we do not encourage anybody to work with high voltage as its dangerous,but anyway these stuffs are done by using a TRIAC if the relay is dc then use a SCR.
    415 volt(AC/DC) is quite dangerous,so be carefull ....
    Good Luck
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    There are details of 7 relays in your material (as far as ciol voltages go). Which do you intend to use? None seem to be rated for 12 amps at the 415 volts. If the application is for something like a motor, you may be better using a heavier device called a contactor - http://www.allaboutcircuits.com/vol_4/chpt_5/2.html
     
  5. devmania

    Thread Starter New Member

    Aug 22, 2010
    17
    0
    Thanks Beenthere ..
    I will be using contactors... but how can i operate these contactors using microcontroller ... what should i use in between contactors and microcontroller . Please help me with this.
     
  6. devmania

    Thread Starter New Member

    Aug 22, 2010
    17
    0
    Thanks for the suggestion , i will be taking preventive precautions .
    My aim is to operate a contactor using microcontroller. The contactor will be connected to a 3-ph induction motor. The contactor coil need 24vDc and can operate at 415v Ac . So i wanted to know which microcontroller should i use and what interface should i make between controller and contactor.
     
  7. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    You wull need a Darlington transistor to handle the relay current. Something like a TIP122 might work. You can get a data sheet at the link - http://www.fairchildsemi.com/pf/TI/TIP122.html

    You will need a resistor between the I/O pin and the transistor base to limit current. Something on the order of 360 ohms would be close. Place a diode across the relay coil So it is reverse biased when the transistor conducts. It will cut the inductive kick when the relay current stops. The relay goes between the 24 volt source and the TIP collector, with the emitter to ground.
     
  8. sage.radachowsky

    Member

    May 11, 2010
    241
    38
    You could also use a logic-level N-channel MOSFET as well.
     
  9. GetDeviceInfo

    Senior Member

    Jun 7, 2009
    1,571
    230
    you best be opto isolating. You don't want any of that nasty voltage/frequency anywhere near your micro. A common setup would be an opto isolator driving a smaller 5-24v relay, which in turn would switch 120vac control voltage, which would in turn pull in your contactor. The 120 control is obtained with a stepdown control transformer. Don't forget to wire your overloads and E stops.
     
  10. devmania

    Thread Starter New Member

    Aug 22, 2010
    17
    0
    Thank you so much sir,
    i got a pic about how to perform it. i will try it and get back to you .
     
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