Featured Articles
Announcing Pi
Technical Specifications
Raspberry Pi FAQs
Win a Pi
Raspberry Pi Wishlist
Actions
Forum Thread Details
  • State Not Answered
  • Replies 5 replies
  • Subscribers 676 subscribers
  • Views 963 views
  • Users 0 members are here
Related

Pi power question driving a stepper motor

knight_rider1977

I'm working on getting a python script to drive a stepper motor (28BJY-48).  When I hook it up to the 5v power on the Pi it basically freezes up.  I added a header on a circuit board to allow me to hook up a 9v power source (9v battery since I don't have any plugs for power supplies yet).  After rebooting I hooked up to the external power source and that resolved the issue and the motor started turning.  I've tested several other things running off just the Pi power and not had this issue, LED lights, 16x2 Backlit LCD screen.  Is there something I need to check with the Pi or is the Motor just a bit too much for the Pi to supply the needed power to the stepper motor?  I also have a external powered USB hub attached to the Pi.  I'm trying to learn more about how electronics work.  My main background is in Computers but I've always had a interest in electronics so anything, including theory, will help me greatly.  I'm just hoping I didn't do something and fried my Pi image

Parents
  • 0

    The ULN2003AN should be fine for driving the motors. They use TTL inputs so will work with the 3.5v from the Raspberry Pi GPIO.

     

    For a basic resistance level then your calculations look good, but motors are inductive loads so don't behave as pure resistors. It is probably sufficient to use those calculations, but if you have a datasheet it should give you maximum actual current depending upon whether a load is connected. It's also important to note whether that is for an individual coil or if there are multiple coils that may be switched on simultaneously (eg. a 4 coil stepper motor may have two coils energised at the same time).

     

    Note that it is the current rating of the power supply that is relevant here and not the voltage. So if you find that the peak current through all your motors exceeds that of the power supply then you need to look for a power supply with a higher current rating, not voltage rating.

Reply
  • 0

    The ULN2003AN should be fine for driving the motors. They use TTL inputs so will work with the 3.5v from the Raspberry Pi GPIO.

     

    For a basic resistance level then your calculations look good, but motors are inductive loads so don't behave as pure resistors. It is probably sufficient to use those calculations, but if you have a datasheet it should give you maximum actual current depending upon whether a load is connected. It's also important to note whether that is for an individual coil or if there are multiple coils that may be switched on simultaneously (eg. a 4 coil stepper motor may have two coils energised at the same time).

     

    Note that it is the current rating of the power supply that is relevant here and not the voltage. So if you find that the peak current through all your motors exceeds that of the power supply then you need to look for a power supply with a higher current rating, not voltage rating.

Children
  • 0 in reply to penguintutor

    K that makes sense.  I'm looking at the datasheet and not having much luck finding information on google to get the light to fully come on (the light in my head is getting brighter though image ). Some of the data makes sense but I'm not seeing a max current.  Is one of the below from the datasheet what I'm looking for or do I need to track down a different datasheet?

     

    Rated voltage: 5VDC

    Number of Phase: 4

    Speed Variation Ratio: 1/64

    DC resistance: 50Ω±7%(25°C)

    Insulated resistance >10MΩ(500V)

    Insulated electricity power 600VAC/1mA/1s