# Copyright (c) 2020 Thomas Holland (thomas@innot.de)
# All rights reserved.
#
# This code is licensed under the MIT License.
#
# Refer to the LICENSE file which is part of the AdvPiStepper distribution or
# to https://opensource.org/licenses/MIT for a text of the license.
#
#
"""
Driver for the popular 28BYJ-48 stepper motor.
The 28BYJ-48 is a small, 5V or 12V stepper motor with an integrated reduction gear which
results in 2048 full steps per revolution of the output shaft. Due to the high
reduction gear (64:1), this stepper motor is rather slow.
Without any hacks (e.g. higher voltage; bipolar mods) and without much load
the 28BYJ-48 should be able to do about 15 rpm or about 500 steps per second.
The 28BYJ-48 is a unipolar motor and is often sold together with a small driver board
based on the ULN2003 Darlington array for less than 3€.
This driver just defines the following parameters for this motor, guessed from this
`datasheet <https://www.digikey.de/de/datasheets/mikroelektronika/mikroelektronika-step-motor-5v-28byj48-datasheet>`__
with the help of the `stepper motor glossary <https://www.anaheimautomation.com/support/stepper_motor_glossary.htm>`__
There are numerous variants of the 28BYJ-48 on the market with slightly different parameters, so
these parameters are on the conservative side. Each can be overriden by providing an optional
dictionary with alternative values to the constructor.
- MAX_SPEED: 650 steps/second (~10 rpm)
- MAX_TORQUE_SPEED: 120 steps/second
- ACCELERATION_RATE: 2000 steps / second^2
- DECELERATION_RATE: 4000 steps / second^2
- FULL_STEPS_PER_REV: 2048 Full steps per revolution
- MICROSTEP_OPTIONS: FULLSTEP or HALFSTEP.
- MICROSTEP_DEFAULT: HALFSTEP
Halfstep is the recommended rate for the 28BYJ-48
Besides the motor characteristics this driver uses colors for the 4 control wires which seem
to be standard for all 28BYJ-48 variants.
- pink / orange for A+ and A-
- yellow / blue for B+ and B-
.. note::
The motor wires should not be connected to the Raspberry directly. To provide sufficient
power to the motor a driver IC like the `ULN2003A <https://en.wikipedia.org/wiki/ULN2003A>`__
should be used.
"""
from advpistepper.driver_unipolar_generic import *
[docs]class Driver28BYJ48(DriverUnipolarGeneric):
"""
:param pink: GPIO pin the pink wire (A+)is connect to (Broadcom / pigpio numbering)
:type pink: int
:param orange: GPIO pin the orange wire (A-) is connect to (Broadcom / pigpio numbering)
:type orange: int
:param yellow: GPIO pin the yellow wire (B+) is connect to (Broadcom / pigpio numbering)
:type yellow: int
:param blue: GPIO pin the blue wire (B-) is connect to (Broadcom / pigpio numbering)
:type blue: int
:param parameters: Optional parameters to override the default values.
:type parameters: dict, optional
"""
_28byj48_defaults: Dict[str, Any] = {
DRIVER_NAME: "28BYJ-48",
MAX_SPEED: 650.0,
MAX_TORQUE_SPEED: 120.0,
ACCELERATION_RATE: 2000,
# TBD: for now an arbitrary number to accelerate to full speed in approx. 1/4 second
DECELERATION_RATE: 3000,
# TBD: somewhat higher than acceleration deu to the internal friction helping with the deceleration
FULL_STEPS_PER_REV: 2048,
MICROSTEP_DEFAULT: HALFSTEP
}
def __init__(self, pink, orange, yellow, blue, parameters: Dict[str, Any] = None):
p: Dict[str, Any] = self._28byj48_defaults # default values
if parameters is not None:
p.update(parameters) # replace defaults with custom values
super().__init__(pink, orange, yellow, blue, parameters=p)