Encoder counting up/down issue using Motor2040

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1

Hi,
I recently bought the Motor2040 board, some MMME motors and some MMME encoders, and I am looking into the counting possibilities of the combined eco-system.
My goal is to turn a motor, for example, 890 counts forwards and then backwards for 890 counts.
Forward counting works fine, however when I reverse the direction of the motor and the encoder, the counting does not count down.
When I initialise the encoder at the beginning as reversed, the counting goes negative which is what I expect.
Unfortunately, I understand the libraries/drivers for the motor2040 and the MMME encoder partially.
So is it possible to keep track of the encoder.count (adding/substracting) when changing the direction of the motor?

Please have a look at this code:

import time
from motor import Motor, motor2040
from encoder import Encoder
from pimoroni import NORMAL_DIR, REVERSED_DIR

MOTOR_PINS = motor2040.MOTOR_A          # The pins of the motor being profiled
ENCODER_PINS = motor2040.ENCODER_A      # The pins of the encoder attached to the profiled motor
GEAR_RATIO = 110
DIRECTION = NORMAL_DIR							# The direction to spin the motor in. NORMAL_DIR (0), REVERSED_DIR (1)

m = Motor(MOTOR_PINS, direction=DIRECTION)
enc = Encoder(0, 0, ENCODER_PINS, direction=DIRECTION, counts_per_rev=GEAR_RATIO*4, count_microsteps=True)
#enc = Encoder(0, 0, ENCODER_PINS, direction=REVERSED_DIR, counts_per_rev=GEAR_RATIO*4, count_microsteps=True)

#Go forward
m.enable()
m.speed(1)

while enc.count() < 890: #445:
    print("Count =", enc.count()," Turn =", enc.turn())   #print current count position while moving forward
    time.sleep(.1)

#Stopped and wait for 3seconds   
m.stop()
print("Count after stopped =", enc.count()," Turn =", enc.turn())   #print current count position when stopped
time.sleep(3)

#Go reverse
m.direction(REVERSED_DIR)
enc.direction(REVERSED_DIR)
m.speed(1)

while enc.count() > 0:
    print("Count =", enc.count()," Turn =", enc.turn())   #print current count position while moving in reverse
    time.sleep(.1)
    
#Stop motor and disable
m.stop()
print("Count after stopped =", enc.count()," Turn =", enc.turn())    #print current count position when stopped
m.disable()

And here is some output:

>>> %Run -c $EDITOR_CONTENT
Count = 0  Turn = 0
Count = 77  Turn = 0
Count = 188  Turn = 0
Count = 299  Turn = 0
Count = 411  Turn = 0
Count = 522  Turn = 1
Count = 633  Turn = 1
Count = 745  Turn = 1
Count = 857  Turn = 1
Count after stopped = 968  Turn = 2
Count = 996  Turn = 2
Count = 996  Turn = 2
Count = 995  Turn = 2
Count = 994  Turn = 2
Count = 996  Turn = 2
Count = 995  Turn = 2
Count = 994  Turn = 2
Count = 996  Turn = 2
Count = 995  Turn = 2
Count = 994  Turn = 2
Count = 996  Turn = 2
Count = 996  Turn = 2
Count = 994  Turn = 2
Count = 996  Turn = 2
Count = 996  Turn = 2
Count = 994  Turn = 2
Count = 996  Turn = 2

I hope that someone can help me further. Thank you for your time.
Guido

2

Hello,
Just a quick followup. The issue is solved…the mistake of installing the encoder disc wrong.
Guido

3

Hi @Guido. Apologies for never seeing your original message. I am glad to hear you identified that the encoder disc was incorrectly oriented. Did you get the MMME shims and solder them on to motors, or were they the pre-soldered ones we sell?

This page (Micro Metal Motor Encoder (MMME) (pack of 2)) does mention:

Note that the magnets will only work one way round - the side with the dots on should be pointing away from the motor.

Was this incorrect for your setup? It’s not entirely impossible for our supplier to have changed the orientation between batches.

4

Hi @ZodiusInfuser,
I had soldered the shims myself onto the motors and installed all the magnet disc, at least consequently, wrong. When I reordered new motors and shims I saw that the orientation of the disc was important…
Best regards,
Guido

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