Controlling AC motor with raspberry

Discussion in 'Embedded Systems and Microcontrollers' started by LightningAle, Jun 6, 2016.

  1. LightningAle

    Thread Starter New Member

    Jun 6, 2016
    5
    0
    Hi,
    I'm new to these electronic projects, I'm doing it for a project in the company I work in, I have to build a test station for testing a marine impeller within a brass pump used for engine cooling. I'm collecting elements and problems of this project and filling my lack of knoledge. Any help will be appreciated.
    The motor has an inverter (of course) but I don't know which kind of IO protocols I can use. In DC brushless I'd use PWM, in this case the motor is also a brushless but driven by inverter which is plugged to 380V.
    Many thanks
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,509
    2,369
    More details on the drive would help, any manual for it should show the control methods available, you couldn't just use a 3 phase motor and a VFD?, they usually give various options for control such as analogue, Modbus etc.
    Max.
     
    Last edited: Jun 8, 2016
  3. LightningAle

    Thread Starter New Member

    Jun 6, 2016
    5
    0
    Thanks for reply.
     
  4. LightningAle

    Thread Starter New Member

    Jun 6, 2016
    5
    0
    Hi Max,
    we may use an inverter with modbus or ethercat input like this
    https://industrial.omron.it/it/products/accurax-g5#features
    I had a conversation with the owner of Laika explorer board which told me we might use PWM digital output. He supposed to use the explorer as a PLC but I'm not sure if it works fine. Can you tell me Your opinion?
    Thank you
     
  5. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,509
    2,369
    The G5 drive appears to use an encoder for feedback?
    Does your motor have one?
    If you just need RPM control and not precise positioning it seems a little over-kill?

    I saw limited I/O but I didn't see much opportunity to use as a PLC, unless you have more info.
    If you need a small PLC you could look at a SmartRelay.
    Max.
     
  6. LightningAle

    Thread Starter New Member

    Jun 6, 2016
    5
    0
    It has an encoder and I agree it is over-kill. Sorry I'm a little bit confused: I can't really understand how I can interface the raspPI( or other PC) to an inverter and command the motor. Consider I have to build a GUI for the touch panel of the operator and make the program run on raspPI. Then I'd make the PI communicate with the inverter, and for this purpose I know I can use a digital output, but I don't know what the inverter "understands"as input information: does ethercat or modbus have something related to this? As far as I understand Ethercat, Modbus are all protocols for controlling inverters from a PLCs. In mere words, how many passages do I need in order to make the motor move from an input of the operator?
    python code (raspPI)->Laika explorer digital output->inverter->internal processing language (not accessible)-> motor
    and for control the motor speed with a sensor:
    motor hall sensor---feedback--->inverter (it adjust automatically the speed with an internal DSP function)-->laika explorer digital in-->raspPI program--->visualization
    or is the program on the rasp PI which have to handle the feedback and regulate the PWM out with an internal function?
    sorry but it will clarify me many things. Also a lecture could help me to learn more in this topic.
    Thank you very much for Your help.
    Ale
     
  7. LightningAle

    Thread Starter New Member

    Jun 6, 2016
    5
    0
    It has an encoder and I agree it is over-kill. Sorry I'm a little bit confused: I can't really understand how I can interface the raspPI( or other PC) to an inverter and command the motor. Consider I have to build a GUI for the touch panel of the operator and make the program run on raspPI. Then I'd make the PI communicate with the inverter, and for this purpose I know I can use a digital output, but I don't know what the inverter "understands"as input information: does ethercat or modbus have something related to this? As far as I understand Ethercat, Modbus are all protocols for controlling inverters from a PLCs. In mere words, how many passages do I need in order to make the motor move from an input of the operator?
    python code (raspPI)->Laika explorer digital output->inverter->internal processing language (not accessible)-> motor
    and for control the motor speed with a sensor:
    motor hall sensor---feedback--->inverter (it adjust automatically the speed with an internal DSP function)-->laika explorer digital in-->raspPI program--->visualization
    or is the program on the rasp PI which have to handle the feedback and regulate the PWM out with an internal function?
    sorry but it will clarify me many things. Also a lecture could help me to learn more in this topic.
    Thank you very much for Your help.
    Ale
     
  8. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,509
    2,369
    Many/most drives only have 0-10v analogue control or maybe Modbus as well, there is a program out there (Mach3) aimed at amateur CNC hobbiest and they use the parallel port for all control so the spindle has a PWM pin which for the aforementioned drives requires a PWM to analogue convertor such as the one below.
    Most μp's have a PWM output which could incorporate the circuit below.
    For Modbus I have used the USART port on a Picmicro to output the data, with a USB or COM port to RS485 adapter, couple of $'s on ebay to control a VFD and 3 phase motor .
    If the motor you have is BLDC with no hall effect sensors etc then you could use a BLDC servo drive such as A-M-C or Aerotech etc.
    A lot depends on how precise of rpm control is needed.
    Is the 380v you mention a 3ph, 1ph or DC supply?
    Max.

    [​IMG]
     
Loading...