Welco Pump, with Adafruit Stepper Motor HAT and rpi

[oswyn123]

Hello, I'm working on a small stepper motor pump project, and was wondering if I was missing something obvious.

I'm using a stepper motor from Welco, tech sheet here:
https://www.welco.net/dcms_media/other/ ... ctguid.pdf
Its the M type of stepper motor, so the range is from 8-24V, current is 300mA max (listed on page 4)

My power supply feeding the hat is a 12V, 10A power supply. I know that the Adafruit HAT had a max rating of 12V, so I'm sticking with this lower end of the power supply for right now (if anyone had any advice on a 24V hat, I'd love to hear it).

When I ran the stepper test code, the motor did some grinding for a split second, then turned off. I haven't been able to get the motor back and running since. Testing resistance between the 2 coils, it appears that this number is similar between each, and there is not any shorting/continuity issues between coils.

Thanks for your time!

[adafruit_support_bill]

The 'M' type pump on the 4th page is not a stepper motor. It is a brushed DC Gearmotor.

Please post some photo showing how you have everything connected - and the code you are using to test.

[oswyn123]

Shoot, you're right- I was going off the original quote when I pulled the model number. The pump type is type BA (Part number: WP10-P4BA2-J4-BP. This can be seen on page 7.

I uploaded a photo of the setup. And here is the starter code I was using:

#!/usr/bin/python
#import Adafruit_MotorHAT, Adafruit_DCMotor, Adafruit_Stepper
from Adafruit_MotorHAT import Adafruit_MotorHAT, Adafruit_DCMotor, Adafruit_Ste$

import time
import atexit

# create a default object, no changes to I2C address or frequency
mh = Adafruit_MotorHAT()

# recommended for auto-disabling motors on shutdown!
def turnOffMotors():
mh.getMotor(1).run(Adafruit_MotorHAT.RELEASE)
mh.getMotor(2).run(Adafruit_MotorHAT.RELEASE)
mh.getMotor(3).run(Adafruit_MotorHAT.RELEASE)
mh.getMotor(4).run(Adafruit_MotorHAT.RELEASE)

atexit.register(turnOffMotors)

myStepper = mh.getStepper(200, 1) # 200 steps/rev, motor port #1
myStepper.setSpeed(30) # 30 RPM

while (True):
print("Single coil steps")
myStepper.step(100, Adafruit_MotorHAT.FORWARD, Adafruit_MotorHAT.SINGLE)
myStepper.step(100, Adafruit_MotorHAT.BACKWARD, Adafruit_MotorHAT.SINGLE)

print("Double coil steps")
myStepper.step(100, Adafruit_MotorHAT.FORWARD, Adafruit_MotorHAT.DOUBLE)
myStepper.step(100, Adafruit_MotorHAT.BACKWARD, Adafruit_MotorHAT.DOUBLE)

print("Interleaved coil steps")
myStepper.step(100, Adafruit_MotorHAT.FORWARD, Adafruit_MotorHAT.INTERLEAV$
myStepper.step(100, Adafruit_MotorHAT.BACKWARD, Adafruit_MotorHAT.INTERLEAV$

print("Microsteps")
myStepper.step(100, Adafruit_MotorHAT.FORWARD, Adafruit_MotorHAT.MICROSTEP)
myStepper.step(100, Adafruit_MotorHAT.BACKWARD, Adafruit_MotorHAT.MICROSTEP)

[adafruit_support_bill]

Ah, that stepper is not going to be compatible with the HAT. It is rated for 1.1A per phase @ 1.76V and has a phase resistance of just 1.6 ohm. So at 12v it will be trying to pull 7.5A per phase which would likely fry the driver chips on the HAT rather quickly since they can only handle 1.2A continuous.

Stepper motor spec sheets can be confusing. The 1.1A/1.76V rating does not really mean that the motor was designed for operation with a 1.76V power supply. Given the extremely low phase resistance, this motor will require a current limiting driver - with the current limit set to 1.1A or less. https://learn.adafruit.com/all-about-st ... he-stepper

For current limiting drivers, we have the DRV8833, but it is only rated for up to 10.8v. https://www.adafruit.com/product/3297
www.pololu.com carries a wider range of stepper drivers with current limiting capability.

[oswyn123]

Thanks so much! That makes much more sense, and I should have looked into this more. I'm now looking a the DRV8880 driver which looks like it does what is needed to meet the higher voltage and current requirements.

Appreciate the assistance!