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Stepper Speed limitations with MotorShield v2?
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Re: Stepper Speed limitations with MotorShield v2?

by theITguyfromNY on Mon Jan 28, 2019 5:49 pm

Got my 324 (motor) and 2348 (HAT) and all are working. First, just for a quick test, I ran it off a 9V battery...just a test, and all is working. (hardware and software). Next biggest question, and this is still on-topic of fastest speed possible here, is what power supply? I have a 12V 1.5A...plugged it in and motor is def. faster...but even after some minor testing the motor is a little warm (My project will certainly beat this motor up a lot more than about 5,000 steps, so I must have a [over]power problem.

Is there someplace (software??) that I am supposed to be configuring power settings for the board/motor? Do I also now need a chomper board (will def. have to research that, if so).

What if I want to add a second stepper to the mix? Will I be soldering in another [separate] power input + and - somewhere on this board (or will this single power source supply for BOTH motors?)

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Re: Stepper Speed limitations with MotorShield v2?

by adafruit_support_bill on Tue Jan 29, 2019 7:07 am

Maximum speed is governed by the speed of the i2c bus. If you read through this thread it is discussed in great detail.

Increasing the supply voltage will increase the motor torque. It will also increase the amount of heat put out by the motor. This is normal and these motors can handle it. The windings are rated for up to 130C.

At 12v, each motor will draw about 700mA. If you add a second motor, you will need a supply capable of 1.4A.

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Re: Stepper Speed limitations with MotorShield v2?

by theITguyfromNY on Fri Feb 01, 2019 5:35 pm

OK. I created what I thought was a very simple test script:

Code: Select all | TOGGLE FULL SIZE
# begin script
from adafruit_motorkit import MotorKit
from adafruit_motor import stepper
kit = MotorKit()

input("Press Enter to start test...")

for a in range(200):
     kit.stepper1.onestep(direction=stepper.BACKWARD, style=stepper.SINGLE)

kit.stepper1.throttle = 0
kit.stepper1.release()

# end script


I've not changed the throttle, as you see there's NO alteration in direction, SINGLE vs DOUBLE vs MICROSTEP, etc...

...and I've confirmed that it is NOT making a complete 360 degree rotation. I'll spare you the photo, but I have it face-up with a coupler, small allen wrench and a needle facing the floor to confirm this. I've tried minor changes to my range #, but the motor is just plain ole not being anywhere near accurate. I saw the thread that your instructions point to about adding diodes directly on the motor to minimize noise, but not sure this applies to steppers, anyway. Given how simple of a test this is, I can't think of anything that would cause this. Is it time to consider this definitely a defect in the motor and/or the board and return these items?
Last edited by adafruit_support_bill on Fri Feb 01, 2019 7:49 pm, edited 1 time in total.
Reason: Please use [code] tags when posting code to the forums

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Re: Stepper Speed limitations with MotorShield v2?

by adafruit_support_bill on Fri Feb 01, 2019 7:50 pm

Please post photos showing your soldering and connections.

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Re: Stepper Speed limitations with MotorShield v2?

by theITguyfromNY on Fri Feb 01, 2019 8:45 pm

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theITguyfromNY
 
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Re: Stepper Speed limitations with MotorShield v2?

by adafruit_support_bill on Fri Feb 01, 2019 9:07 pm

You do have some suspect solder joints there. There are several which have not flowed well onto the solder pads. This guide has some tips on identifying and fixing common soldering problems: http://learn.adafruit.com/adafruit-guid ... n-problems

Other possible issues are:
* You are using SINGLE, which is the weakest possible stepping mode. Use DOUBLE instead for more torque
* There is no inter-step delay in your loop. Stepper torque is inversely proportional to speed.

Insufficient torque can result in missed steps.

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Re: Stepper Speed limitations with MotorShield v2?

by theITguyfromNY on Fri Feb 01, 2019 9:13 pm

Thanks.

1) I see the couple of solder points you mean and I can and will make those minor adjust, just for thge long-term of it.

2) inter-step delay: (and problem solved, really!) added import time and time.sleep(.01)? Works great now! Very interesting. It's like a hack to slow the I2C bus speed down...and to-that-note, when I change the time.sleep to (.001) I get the same strange endpoint problem [as if w/o it at all].
--update (edited post)...I changed the I2C bus speed (config.txt; there's a thread about it somewhere) up to 400000. So I'm kinda dividing by 4 then multiplying by 4. Got a laugh outta that, but it brings me back to, literally 60rpm. ( added time functions before and after onestep code and, literally it's 1 second to make the 360...so good enough for me, I think!

And...interesting on torque...I think you're saying, if I don't have ENOUGH torque, the motor can be...wonky. (that's strange to me; I would think this guy's been tested and def. works without torque and then starts getting wonky only after it hits above the recommended max torque (that's what I would consider "max torque" to be).

Thank you, sir. Happy...helping folks! :-)

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Re: Stepper Speed limitations with MotorShield v2?

by adafruit_support_bill on Sat Feb 02, 2019 7:26 am

Good to hear that is working for you . Thanks for the follow-up.

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Please be positive and constructive with your questions and comments.