Powering stepper motor directly


12 posts
by adam63 » Fri May 26, 2017 10:41 pm
Hey, I need a setup that will allow me to create a horizontal push process with the raspberry pi. I've found the below which looks ideal for what I need although I'm not sure how I'd actually connect it to the pi. I've used stepper motors in the past but they've had 5 connection pins instead of 4 and have come with connection board that I could then connect up directly to the pi.

Do I need any additional components to run this?

http://www.ebay.co.uk/itm/DC-4V-9V-2-Phases-4-Wires-18-Degrees-Drive-Stepper-Motor-Kit-Screw-Nut-Slider/222514306874?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D2%26asc%3D44293%26meid%3Ddc969d6e29f54d5dbd43bea3ed84d9bc%26pid%3D100005%26rk%3D4%26rkt%3D6%26sd%3D322446283412
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by pcmanbob » Sat May 27, 2017 9:41 am
Hi.

I would suggest that you are going to need a driver board like you have used in the past to connect this to the pi,
but it needs to be one specificity for a DC 4V-9V 2 Phases 4 Wire stepper motor.

I did do a quick search on ebay but could find non that would interface this type of stepper motor to the pi.
may be a more detailed search with different options would be more fruitful.
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by Moe » Sat May 27, 2017 11:23 pm
Google for a A4988 module. Very easy to use, should do the job.
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by Burngate » Sun May 28, 2017 8:56 am
I don't know which steppers with five connections you have experience with.
However, the one you've linked to is just a bare motor, with two windings each taking 4v - 9v at 500mA, which the Pi cannot supply, so you will need some electronics as an interface.
Specifications:
* Micro Sliding table fit for DIY laser engraving machine as its XY axis
* Motor Type: 2 phase 4 wire
* Driving Voltage: DC 4-9V / 500mA
* Step Angle: 18 degrees
* Screw Length: 90mm / 3.5inch
* Screw Diameter: 3mm / 0.1inch
* Slider Width: 15mm / 0.6inch
* Effective Stroke: 80mm / 3.1inch
* Screw Pitch: 0.5mm / 0.02inch

The motor steps 18 degrees, or 1/10th of a full turn, each time the current in one winding reverses, and a full turn moves the nut 0.5mm, so one step is 0.05mm (50μm)
If that's as accurate as you want, then a simple H-bridge would suffice. If not, then Moe's device would work.
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by drgeoff » Sun May 28, 2017 9:18 am
Burngate wrote:I don't know which steppers with five connections you have experience with.
However, the one you've linked to is just a bare motor, with two windings each taking 4v - 9v at 500mA, which the Pi cannot supply, so you will need some electronics as an interface.
Specifications:
* Micro Sliding table fit for DIY laser engraving machine as its XY axis
* Motor Type: 2 phase 4 wire
* Driving Voltage: DC 4-9V / 500mA
* Step Angle: 18 degrees
* Screw Length: 90mm / 3.5inch
* Screw Diameter: 3mm / 0.1inch
* Slider Width: 15mm / 0.6inch
* Effective Stroke: 80mm / 3.1inch
* Screw Pitch: 0.5mm / 0.02inch

The motor steps 18 degrees, or 1/10th of a full turn, each time the current in one winding reverses, and a full turn moves the nut 0.5mm, so one step is 0.05mm (50μm)
If that's as accurate as you want, then a simple H-bridge would suffice. If not, then Moe's device would work.

One step is 0.025 mm. (18 degrees is 1/20 of a full turn.)
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by Burngate » Sun May 28, 2017 9:25 am
Doh!

Is the rest of my arithmetic ok? 25μm seems remarkably small - and possibly swamped by any back-lash
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by adam63 » Wed May 31, 2017 7:34 pm
Moe wrote:Google for a A4988 module. Very easy to use, should do the job.


Looks good, £2.72 on ebay! Already got the cables to hook it up. Would I need an external power source to power this or would the pi be able to directly?
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by Burngate » Thu Jun 01, 2017 10:47 am
Possibly.

The chip itself won't take much - a few mA - but the motor can take 500mA.
Your power supply may or may not be able to provide that as well as the Pi and whatever else you've got attached.
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by Moe » Sun Jun 04, 2017 10:58 pm
Don't power it directly from the Pi. You could power it from the same source, if the amps add up, or use a higher voltage for better torque. Steppers aren't too fussy about voltage; it the current that matters and the module allows you to limit it to whatever the motor needs.
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by adam63 » Mon Jun 12, 2017 8:12 pm
Thanks for the replies, sorry it's taken so long to respond!

Is there an issue powering it directly from the pi's power pin? I believe my power source into the pi is strong enough to handle that. If not what would be my best bet at powering it?

Also I don't suppose you know of any guides I can follow or what to search for? I've used stepper motors before if it's basically the same process as that.
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by pcmanbob » Mon Jun 12, 2017 8:39 pm
adam63 wrote:Thanks for the replies, sorry it's taken so long to respond!

Is there an issue powering it directly from the pi's power pin? I believe my power source into the pi is strong enough to handle that. If not what would be my best bet at powering it?

Also I don't suppose you know of any guides I can follow or what to search for? I've used stepper motors before if it's basically the same process as that.



The motor spec says 500mA if you try pulling that from the GPIO pin you might find the Pi rebooting due to sudden voltage fluctuations, its always wise to use a separate power supply for running motors of any kind, rather than trying to run them direct from the Pi. Any psu with a suitable voltage rating able to supply 500mA or greater should be fine.

as for guides just try googling "connecting pi to a4988" if that the driver you settle on.
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by adam63 » Mon Jun 19, 2017 6:11 pm
pcmanbob wrote:
adam63 wrote:Thanks for the replies, sorry it's taken so long to respond!

Is there an issue powering it directly from the pi's power pin? I believe my power source into the pi is strong enough to handle that. If not what would be my best bet at powering it?

Also I don't suppose you know of any guides I can follow or what to search for? I've used stepper motors before if it's basically the same process as that.



The motor spec says 500mA if you try pulling that from the GPIO pin you might find the Pi rebooting due to sudden voltage fluctuations, its always wise to use a separate power supply for running motors of any kind, rather than trying to run them direct from the Pi. Any psu with a suitable voltage rating able to supply 500mA or greater should be fine.

as for guides just try googling "connecting pi to a4988" if that the driver you settle on.


Nice one thanks, from what I can see online I'll need a breadboard to connect the power to the a4988 and can't go direct.
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