BLDC Motor Control Circuit

Discussion in 'Automotive Electronics' started by liamneeson248, May 14, 2019.

  1. liamneeson248

    Thread Starter Member

    Jan 11, 2016
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    I have a BLDC motor rated at 20A 48VDC which i want to control but with arduino.
    i am having some confusions which i want someone to address.

    1-Is it okay to just control the motor with N Channel Mosfet and arduino with sequence of HIGH LOW (without using any motor driver or whatever)?
    2-Should i use N Channel or P Channel Mosfet individually to control the motor or should i use N channel on LOW side and P Channel on HIGH side?
    3-Do i need a motor driver? is it best to use it?
    4-if i use a motor driver, will the current will be passed from the motor driver to the motor or do i need to connect mosfet before driver and driver will only be used to send signal to the mosfet?
    5-there are three phases of BLDC, one will be used as high and second one will be used as LOW at one time, so the third one will be free right? do we have to use that phase to calculate back EMF? where should i be able to calculate the back EMF?

    Thanks in advance and sorry if my english is bad.
     
  2. cmartinez

    AAC Fanatic!

    Jan 17, 2007
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    Yes, I think you should use a commercially available driver for this application. BLDC motors work on the principle of synchronizing the power applied to the stator windings so as to impel the rotor. For that purpose, they have encoders or some other type of sensing components in them that are used to determine the position and speed of the rotor and so know how and when to apply power, and for how long. As you might've already guessed, a BLDC driver is quite a project by itself.
     
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  3. liamneeson248

    Thread Starter Member

    Jan 11, 2016
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    is a BLDC driver is directly capable of passing 20A current from it?
    and if a motor does not have any sensor or encoder in it do we have to install it on motor or does the BLDC will have it in itself?
     
  4. cmartinez

    AAC Fanatic!

    Jan 17, 2007
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    Yes, a properly sized driver can easily deliver 20 A of current, but you have to make sure it has that capability by studying its datasheet.

    The BLDC motor normally has the required sensors within itself. That is why they have so many cables coming out of them. In large motors, it's easy to distinguish the sensor cables from the power ones. The latter normally being of a larger diameter, to allow for greater current.
     
  5. cmartinez

    AAC Fanatic!

    Jan 17, 2007
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    Here's an interesting bit, most computer fans use bldc motors. If you take one apart you will notice its driver circuitry, and also that they have a hall sensor in them to determine their actual speed. They're so simple that they don't use an encoder, but the hall sensor's switching frequency allows the driver to know the motor's rpm, giving it enough information to decide if it should either apply more or less power, or to shut it off entirely.
     
  6. liamneeson248

    Thread Starter Member

    Jan 11, 2016
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    I want to control an DC Compressor which have a BLDC motor in it but only 3 wires are coming from it, even the motors that are being used for RC purposes have 3 wires and nothing more, so that is what making me confuse.
     
  7. cmartinez

    AAC Fanatic!

    Jan 17, 2007
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    Are you sure it's a bldc motor, and not a 3-phase induction one? Do you have a pic of the motor and its plate?
     
  8. liamneeson248

    Thread Starter Member

    Jan 11, 2016
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    This is the motor and according to google it is a rotary compressor, but all the circuit that was originally driving it is seems to be BLDC driving circuit with Mosfets and all.
    [​IMG]
     
  9. bertus

    Administrator

    Apr 5, 2008
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  10. cmartinez

    AAC Fanatic!

    Jan 17, 2007
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    Try googling the motor's model and its brand, see if you can find its datasheet.
     
  11. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Seems to be a Oriental company making BLDC HVAC motors, many or used now for HVAC fan control such as the GE ECM motors, even the main motors in washing machines, such as the Fischer-Paykel outrunner.
    Most of these do not use any physical rotor sensor, but sense feedback from the effect of rotor position.
    A short initial exercise of the motor is carried out in order to establish this.
    For app notes, check out the Picmicro site, there is quite a few there.
    Max.
     
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