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Little Step-U Step-Motor Selection and/or Modification — Parallax Forums

Little Step-U Step-Motor Selection and/or Modification

motionpotionmotionpotion Posts: 2
edited 2010-11-09 18:06 in BASIC Stamp
I’m building a solar-tracking device based on the TSL230 light to frequency converter and the Little Step-U Motor Controller. My issue is matching the voltage and current to an existing Unipolar-Stepping-Motor and be within safe operating levels.

I’m 100% newbie to the Little Step-U and my electronics background has been described as knowing enough to be dangerous! As, I do have some solid experience in almost burning down the house! :smhair:

The motor supplied with this wicked awesome rotary table available on eBay; http://cgi.ebay.com/CNC-Rotary-Table-Stepper-Motor-drive-/330451658228?pt=LH_DefaultDomain_0&hash=item4cf07425f4#ht_500wt_878
It appears to have a Stepping-Motor I hope to adapt to work with the Little Step-U. The Shinano Kenshi STP 58D212 motor is rated for 2.2VDC 3 amps/PH.

I can readily make the required 2,2v using a 3-pin voltage regulator and a 12V lead-acid battery both commonly available. But, when selecting the regulator, and adding up the loads, I found a potential issue! When reading over the Little Step-U specs it says the motor must have a minimum motor resistance of 2.8 OHMS. (This motor is rated at 1.36 OHMS in unipolar mode, and the preferred 2.72 OHMS in the bipolar mode.) And from what I understand the Little Step-U will only drive unipolar motors.

My questions are, since the stepping motor will be used intermittently for only a few moments an hour, can I use a power resistor in series to increase the motor rated OHMS and design my power supply to compensate? What are the odds of frying the Little Step-U or the motor doing this? Will it even work? Should I get the fire extinguisher ready first?

Is this a viable solution? Are there another means of solving this problem? Can I simply use the Shinano motor as is? Perhaps I'm beating a dead horse, and should try selecting a new motor?

Can anyone help me?

Thanks!

Comments

  • $WMc%$WMc% Posts: 1,884
    edited 2010-11-05 20:18
    motionpotion wrote: »
    I’m building a solar-tracking device based on the TSL230 light to frequency converter and the Little Step-U Motor Controller. My issue is matching the voltage and current to an existing Unipolar-Stepping-Motor and be within safe operating levels.

    I’m 100% newbie to the Little Step-U and my electronics background has been described as knowing enough to be dangerous! As, I do have some solid experience in almost burning down the house! :smhair:

    The motor supplied with this wicked awesome rotary table available on eBay; http://cgi.ebay.com/CNC-Rotary-Table-Stepper-Motor-drive-/330451658228?pt=LH_DefaultDomain_0&hash=item4cf07425f4#ht_500wt_878
    It appears to have a Stepping-Motor I hope to adapt to work with the Little Step-U. The Shinano Kenshi STP 58D212 motor is rated for 2.2VDC 3 amps/PH.

    I can readily make the required 2,2v using a 3-pin voltage regulator and a 12V lead-acid battery both commonly available. But, when selecting the regulator, and adding up the loads, I found a potential issue! When reading over the Little Step-U specs it says the motor must have a minimum motor resistance of 2.8 OHMS. (This motor is rated at 1.36 OHMS in unipolar mode, and the preferred 2.72 OHMS in the bipolar mode.) And from what I understand the Little Step-U will only drive unipolar motors.

    My questions are, since the stepping motor will be used intermittently for only a few moments an hour, can I use a power resistor in series to increase the motor rated OHMS and design my power supply to compensate? What are the odds of frying the Little Step-U or the motor doing this? Will it even work? Should I get the fire extinguisher ready first?

    Is this a viable solution? Are there another means of solving this problem? Can I simply use the Shinano motor as is? Perhaps I'm beating a dead horse, and should try selecting a new motor?

    Can anyone help me?

    Thanks!
    '
    This might be of help to you. (JPEG below)I haven't tried this with the Little Step-U module, But I think it should work.
    the TIP125's are good for 5 amps each when heat-sinked.
    '
    I like to use FUSES to prevent melt-downs.
    '
    P.S. The Highside Driver circuit is from and old SXB program From Jonny Mac,I just added a diode and 3 more circuits to make it work with a L293N. I had a note giving credit to Jonny Mac in the bitmap but I didn't see in the JPEG after converting it.I just wanted to make sure credit was given.
    WMcDriver_L293N.JPG
    1212 x 884 - 60K
  • motionpotionmotionpotion Posts: 2
    edited 2010-11-08 10:15
    Thank You!

    I think your right, isolating the signals with the amplifier circuit is definitely the safest option to avoid damaging the Little Step-U controller.

    I’m laying out the High-Side-Driver-Circuit now and hope to build it today. However I did notice something that raised a flag. In you schematic you show the TIP125, a PNP by default wired in a typical NPN fashion with positive polarity. Being a complimentary device that uses the Darlington transistor configuration, I believe it would require reverse polarity to use as an NPN.

    I’m going to use a TIP120 instead wired like your schematic, as it is by default a NPN and has all the same characteristics, including Hfe at 1000.

    A schematic typo? Or am I way off base? :confused:

    Interesting note:

    Again, I'm new to this stepping-motor stuff and I asked a supplier of stepping-motors, power supplies, and driver boards, just how do they get 2.2V @ 5 AMPS? He mentioned to me that some 12V stepping-motor power supplies are capable of chopping the voltage and supplying only the current required?

    Anyone ever heard of that?

    Also, I was hoping someone would have some insight in regards to simply adding power resistors to the motor to modify the motor’s resistance?

    Thanks a million, you people are great!
  • $WMc%$WMc% Posts: 1,884
    edited 2010-11-09 18:06
    motionpotion wrote: »
    Thank You!

    I think your right, isolating the signals with the amplifier circuit is definitely the safest option to avoid damaging the Little Step-U controller.

    I’m laying out the High-Side-Driver-Circuit now and hope to build it today. However I did notice something that raised a flag. In you schematic you show the TIP125, a PNP by default wired in a typical NPN fashion with positive polarity. Being a complimentary device that uses the Darlington transistor configuration, I believe it would require reverse polarity to use as an NPN.

    I’m going to use a TIP120 instead wired like your schematic, as it is by default a NPN and has all the same characteristics, including Hfe at 1000.

    A schematic typo? Or am I way off base? :confused:

    Interesting note:

    Again, I'm new to this stepping-motor stuff and I asked a supplier of stepping-motors, power supplies, and driver boards, just how do they get 2.2V @ 5 AMPS? He mentioned to me that some 12V stepping-motor power supplies are capable of chopping the voltage and supplying only the current required?

    Anyone ever heard of that?

    Also, I was hoping someone would have some insight in regards to simply adding power resistors to the motor to modify the motor’s resistance?

    Thanks a million, you people are great!
    '
    motionpotion:
    '
    You were rite.My TIP125 should have been PNPs not NPNs.
    '
    Sorry for the confusion.
    '
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