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Help with connecting&controlling THK kr20 Linear Actuator

Discussion in 'Sensors and Actuators' started by ddwins, Sep 9, 2016.

  1. ddwins

    ddwins

    4
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    Sep 9, 2016
    Hello all ,

    I found the above motor and i would like to use it.
    I'v uploaded a couple pictures of the motor and it's connectors and i have some questions:
    1. How do I connect the motor to a power supply?
    2. What is the grey connector (pic 1)?
    3. If i connect the motor with a serial port (pic 1) to c computer , how can i control its speed ?

    Thank you for your help
     

    Attached Files:

  2. Minder

    Minder

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    596
    Apr 24, 2015
    Without the manuf. instructions you may have to do some reverse engineering, I would think you will have two conductors for the motor, the others being overtravel limits, could be hall sensors.
    It should be relatively easy to trace everything out if you have a meter.
    The speed will depend on what voltage you apply to the motor, on average these are between 6vdc and 24vdc.
    According to a search, many of these models are fitted with stepper motors.If so you will need a suitable stepper controller.
    M.
     
  3. Alec_t

    Alec_t

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    Jul 7, 2015
    Oddly, the manufacturer's web-site has loads of info on mechanical details of their actuators but no info (at least, none that I could find) on their electrical connections/power requirements!
     
  4. Minder

    Minder

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    Apr 24, 2015
    All the sites that sell them appear to either sell with various manf, stepper motors or with no motor at all, I suspect that these are sold initially without motor and customized by the end user etc.
    OP, if the motor does not appear to have any brushes and shows more than 2 conductors, it is most likely a stepper..
    M.
     
  5. ddwins

    ddwins

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    0
    Sep 9, 2016
    Okay so 2 options from my point of view:
    1.buy stepper controller:
    From videos I have seen , I need to connect the motor to a control board and on the control board there will be a variable resistor (in the form of switch or something similar) that basically controls the speed of the engine, if
    I want to control the speed of the engine from a computer , how can i do that if i connect the motor to the control
    board i mentioned above?
    2.Connecting the motor with Serial Port:
    Is there any danger of burning the motor if i connect it with the Serial Port connector to a computer (see pic 1)?

    Thanks alot for the help!
     
  6. Minder

    Minder

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    Apr 24, 2015
    To size the stepper motor controller you will need to find out if it is Bi-polar or uni-polar. and motor characteristics, current/voltage etc.
    If you can find a driver a simple speed control can be made with a 555 bi-stable oscillator, there are many designs out there via Google.
    M.
     
  7. ddwins

    ddwins

    4
    0
    Sep 9, 2016
    Ok, few more questions.
    in this link you will find the data sheet for the motor connector - http://www.robotstorehk.com/soccer/doc/ie2-512.pdf
    my question is , if i plug in 5V dc to the VDD Enc input , ground to GND Enc input , what other inputs i need to connect in order to activate the motor.
    what does "Motor +" and "Motor -" mean? (bottom of page 1 in the pdf file)
     
  8. Minder

    Minder

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    Apr 24, 2015
    They appear to be micro DC motors, the + and - are the motor power, which if ordinary DC motor you can reverse polarity to change motor direction, the other signals are for a quadrature encoder, if needed.
    The encoder output is shown with the motor +&- signals shown, if the motor polarity is reversed, so is the encoder signal phase to indicate direction.
    They also show a BLDC motor version, as well as the micro brushed motor.
    M.
     
    Last edited: Sep 15, 2016
  9. Minder

    Minder

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    Apr 24, 2015
    Incidentally you do not need the encoder signals and supply to it unless you are using some kind of closed loop feed back system.
    M.
     
  10. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    The six-wire ribbon cable appears to connect (also) to a 9-pin DB9 connector, pin-out unknown, sex of connector unknown (but typically would be male pins for application of power). The DB9 connector is NOT a serial port connector. The 6-pin gray female connector would typically mate with square header pins soldered to a circuit board. You would use the DB9 connector in lieu of the other connector if that is your pleasure. In either case, custom circuitry is required.

    Exactly where would you connect it? The typical DB9 serial port does not have voltages or logic levels compatible with the motor and encoder you linked to here. This appears to be a DC micromotor. Here is a quote from the page you linked: "Details for the DC-Micromotors and suitable reduction gearheads are on separate catalog pages."

    Please provide a link to the appropriate page for the motor you are using if you want us to provide information on how to drive the motor. The encoder is straightforward, providing quadrature TTL-compatible outputs that you can apply to an up-down counter or (if fast enough) decode for direction, speed, and rotation angle with a microprocessor. Depending on what you want to DO (which you have yet to tell us) the encoder may not be necessary. See @Minder post #9.

    Also, so we can properly inform you, what is your level of electronics experience? Ever tried to interface a motor (any kind) to a personal computer? Arduino? Raspberry Pi? Are you comfortable and experienced with breadboarding circuits? Can you read schematics? Can you construct circuits from schematics?

    Hop
     
  11. ddwins

    ddwins

    4
    0
    Sep 9, 2016
    Dear hevans1944,
    Daniel is my name and Mechanical Engineering is my game.
    A bit of information and purposes:

    Level of electronics: Some experience
    Interfaced a motor before: No
    Comfortable and experienced with circuit: Yes
    Ability to read schematics: Yes
    Ability to construct circuits from schematics: Hopefully

    I am currently working on a project of building a setup that allows me to hold optic fibers, stretch them and contract with the help of the motors (two of them) and the control will be done from a computer.

    These motor were inherit to me from a previous lab and I am trying to figure out how to control them.
    I didn't get any information along with them, I got only the box they were in and nothing else, any additional information like the Data Sheets I provided were found online.

    Now, the DB9 connector (Male) that you saw in the picture is irrelevant at the moment.
    I am trying to make the motors work to see if they are in tact.

    First experiment:
    I used a Waveform Generator and set the VDD on 5V.
    I plugged in the output of the Waveform to the six-wire ribbon at entrances 3&4 (GND and VDD respectively shown in the encoder's Data Sheet) it didn't work.

    Questions:
    What does MOTOR + and MOTOR - mean?
    What kind of data can I send to CHANNEL A/B?

    Thank you very much for the elaborate response and the quick reply.

    P.S
    Here is another information page I found during my quest: http://www.micromo.com/1516t012sr.html
     
  12. Minder

    Minder

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    Apr 24, 2015
    The motor just requires a 5v DC supply the + and - refer to the voltage polarity that will give you the phase of the quadrature signal, reverse + - voltage will reverse direction of the motor and reverse the output phase of the encoder , (Google quadrature encoder for more info).
    The encoder is entirely electrically separate from the motor, it is a feedback or position indicator.
    IOW A & B are output not inputs.
    When used in a positioning system, the encoder to controller is called a PID loop (something more to Google)!.
    M.
     
    hevans1944 likes this.
  13. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    What did you expect to happen? Vdd and GND are there to supply 5 V DC to the electro-magnetic encoder.

    The encoder consists of a magnetic disk, mounted on the motor shaft, that is magnetized around its circumference with alternating north and south poles that pass by two Hall-effect sensors as the motor shaft turns. These sensors produce square-wave TTL logic-level outputs on channels A and B. Because of the placement of the Hall sensors with respect to the alternating magnetic poles on the disk, the signals are in quadrature with each other. This means that as the motor shaft rotates the square waves from one channel are displaced by 90 degrees with respect to the square waves from the other channel. You can readily observe this by connecting the A and B outputs to two logic-level LED drivers, one LED for each channel, and turning the motor shaft by hand. Be sure to apply a well-regulated and filtered +5 V DC power supply output to pin 4 (Vdd) and pin 3 (GND). Polarity of power supply connections is important: positive to Vdd and negative to GND. Depending on which model encoder you have (you didn't say), there will be 64, 128, 256, or 512 pulses per revolution of the motor shaft.

    You can also apply power to the motor to make the shaft turn. You do this by applying a constant-voltage DC power supply output to pins 1 and 2. The polarity marked for those two pins will result in clockwise rotation of the motor when viewed from the face of the motor case. Actual applied polarity depends on which way you want the motor shaft to rotate. Reversing the polarity will reverse the motor shaft direction. Depending on the specific motor you have (which you did not specify) the motor will require 6, 9, or 12 V DC to reach a no-load speed of 12,800 to 12,900 revolutions per minute. If the highest resolution encoder (512 pulses per revolution) is attached to a 12 V DC motor, the pulses from channels A and B will occur at (512) x (12,900) pulses per minute = 6,604,800 ppm = 110,080 pps. This should be easily observable on an oscilloscope connected to channel A or channel B. If you have a dual-channel oscilloscope, you can connect channel A to one channel and channel B to the other channel. This will allow you to observe the quadrature nature of the two waveforms. Other encoder resolutions will produce lower frequency pulses for the same motor speed.

    You can determine which (maximum) voltage to apply to the motor by measuring the resistance between pins 1 and 2. The motor datasheet provides rated voltage versus motor resistance information: 15.2 Ω, 32.5 Ω, and 60 Ω for 6 V, 9 V, and 12 V motors respectively. Under some pulse-width-modulated driving conditions, the applied peak voltage may be greater than the rated steady-state DC voltage as long as (1) the maximum power dissipated in the motor and its internal temperature rise remain within limits specified on the datasheet and (2) the voltage does not cause electrical breakdown of the motor wire insulation. The latter parameter is not specified on the datasheet, but typically peak voltage for PWM is two to four times the steady-state DC voltage.

    Driving the motor with a PWM circuit maximizes the torque available at low speeds and minimizes unnecessary power dissipation.

    Well, that's pretty vague and hard-hitting. How do you propose to control the tension in the fibers? AFAIK, fibers don't compress much, although they should contract after stretching if their elastic limit isn't exceeded. Will you be measuring optical properties of the fibers while stretching and contracting them, or is this just a simple fatigue test? Either way, you need some way to control the position of the motor-driven slide. You could use the optical encoder for this but there may be backlash problems associated with the lead screw when you reverse directions. Better, perhaps, would be to control tension in the fiber by measuring it with a load cell, perhaps attached via a cantilever to the fiber. Or you can make your own with piezo-resistive or traditional strain gauges. Many mechanical details missing that will probably affect how you control the motor. And why do you need two motors?

    Hop
     
  14. Minder

    Minder

    2,876
    596
    Apr 24, 2015
    Not that I think you will even need an encoder for your application, but it is also often the practice to increase the resolution of the encoder by either 2x or 4x, this is done by reading either two rising or falling edges or all 4 edges for x4 resolution.
    You also need to measure the pitch of the screw in order to work out what RPM you require for the rate of movement of the actuator.
    M.
     
    hevans1944 likes this.
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