Help identifying motor type

Discussion in 'General Electronics Chat' started by davidr41, Jan 27, 2012.

  1. davidr41

    Thread Starter New Member

    Jan 27, 2012
    6
    0
    Hello All,
    I have scavenged 2 motors from old hard drives, but I am unclear on exactly what type they are. They each have 3 leads, the center seems to be a common pin. When I apply voltage across pin 1 and 2 (counting from left to right) the motor rotates maybe a 12th of the way around in the one direction, if I apply voltage across pings 2 and 3 it rotates the same amount in the opposite direction.

    I beleive this makes them stepper motors, but I am unsure whether this means they are unipolar or bipolar. I have attempted to read several tutorials on stepper motors but none seem to mention 3 lead motors.

    Can anyone help me figure out which type I have and give me a general idea of the sequence the leads should be energized in inorder to cause it rotate fully in either direction

    I'd like to eventually use them in a robotics project, perhaps free moving or line following robot.
     
  2. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    Are you applying voltage directly to the spindle motor, or to the controller board that has the spindle driver on it?

    Sounds like a 4 wire stepper, with the 4th wire being ground return, not entirely sure on that though, but check for resistances between each wire and ground/case (3 measurements), as well as resistance between each wire (6 measurements).

    There is a HOWTO guide on using them for working with lasers and POV clocks, find those projects and they may also describe the working.
     
  3. shortbus

    AAC Fanatic!

    Sep 30, 2009
    4,000
    1,512
    They are most likely BLDC motors. They take a 5VDC on one lead for the on-board driver, voltage for the motor coils on one lead, and ground. That should be the three wires connections. But you would need to figure out which is which from the circuit they come from.
     
  4. davidr41

    Thread Starter New Member

    Jan 27, 2012
    6
    0
    I'm attempting to post a picture, in case that helps. I'm very new to electronics, so if I am not providing adequate info, please let me know and I will try to post it.

    One other piece of info: Resistance across pins (counting from left to right) 1 & 2 is 3.1 ohms, 2&3 = 3.1ohms, 1 & 3 = 3.1 ohms.

    thanks in advance for your help.
     
  5. Experimentonomen

    Member

    Feb 16, 2011
    331
    46
    These are three phase sensorless brushless dc motors. You need a 3phase sensorless bldc driver to run them.
     
  6. shortbus

    AAC Fanatic!

    Sep 30, 2009
    4,000
    1,512
    From the hard drives I've torn apart, there is a driver board built in to the end bell of the motor. The board has the Hall sensors and driver chip mounted on it.
     
  7. Experimentonomen

    Member

    Feb 16, 2011
    331
    46
    No they don't, on the pics i can see the wires from the motor windings coming up though a hole and terminate on the three metal prongs.

    These are 3phase snsorless and nothing else, you can run them with a 3phase sensorless brushless ESC for model aircraft use.

    The only sensored hdd motors i've seen had atleast eight wires, 3 wires for the motor windings, 3 for the hall effect outputs and two for powering the hall effect sensors.

    The others have had 3 wires for the motor windings and eight wires for the hall effect sensors which needed external amplifiers as well as a bias current to produce a usable signal.
     
  8. davidr41

    Thread Starter New Member

    Jan 27, 2012
    6
    0
    Here are the values:
    1&2 = 3.1 Ohms
    2&3 = 3.1 Ohms
    1&3 = 3.1 Ohms
    1 and case = no value
    2 and case = no value
    3 and case = no value
    i.e connecting any of the 3 pins to the case will give no tone on a continuity test.

    When I applied voltage (5V)across 1 & 2 and 2 & 3, it was directly to the pins on the motor. The motor is no longer connected to the original controller.

    Very brief pulses of voltage (1/2 second or less) between any two of the 3 pins will cause it to spin briefly, but sustained voltage across the same two pins will cause it to jerk and stop.
     
  9. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    That was what I was wondering, if he was applying voltage to the motor directly, or through the board connected. I guess we know the answer now.
     
  10. davidr41

    Thread Starter New Member

    Jan 27, 2012
    6
    0
    So the consensus is that this is a 3 phase sensorless brushless DC motor?

    Would this using these motors make sense as a choice to drive a small robot? I've been experimenting with building a simple H bridge controller, but I am not clear if that sort of thing is applicable to this type of motor.
     
  11. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    There should be a controller board between the logic board and the motor, can you find it?

    Otherwise, a 3 phase oscillator can be made, there's a thread on that topic now in This thread
     
  12. Experimentonomen

    Member

    Feb 16, 2011
    331
    46
    These motors are useless for anything other than their intended purpose.

    Making a sensorless driver is very hard and these motors are very weak.

    For robotics i'd recommend regular brushed dc motors as their very easy to control.

    Or bldc motors with the driver built in that only need a DC voltage, a direction and speed signal, but these are generally very expensive and pretty big.
     
  13. davidr41

    Thread Starter New Member

    Jan 27, 2012
    6
    0
    Experimentonomen,

    Is the usability issue with these hard drive motors a matter of low torc? Is that why they aren't very good for robots use?

    This may be a naive question, but couldn't something like an arduino or propellor board control the motor via software and transistors connected to one of their output pins and external power source?

    One other question, could the motor from an inkjet printer be re-purposed to drive small robot? I happen to have a broken printer sitting in the attic.

    Also, thank you to everyone who has taken the time to answer my question. I appreciate all of the help!
     
  14. davidr41

    Thread Starter New Member

    Jan 27, 2012
    6
    0
    Oh one other thing, to answer the question about the controller chip. I believe the controller is a texas instruments chip SH6950 D. The full text on the chip is (ti logo )980 B SH6950 D 39C7JRTA. I couldn't seem to find a data sheet.
     
  15. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    If you search YouTube Videos, you'll find a couple of projects where they cut a slot in the disc, and put LEDs in the slot, making a pretty cool looking and compact POV clock or message display.

    I've also seen them used to control lasers by running two at right angles to each other, at varying speeds to do the scanning.
     
Loading...