nodemcu_stepper

Nodemcu(esp8266) lua module to simplify driving a unipolar stepper motor 28BYJ-48 when using ULN2003 Driver. With this module you can drive a stepper motor in 3 lines like this

stepper  = require ('stepper')
stepper.init({5,6,7,8})
stepper.rotate(stepper.FORWARD,2500,5,0,function () print('Rotation done.') end)

As you can see, your code trigger rotate and let the module finish rotation and trigger callback.

Background

I needed a simple lua module (with callbacks) that I can use to drive the cheap 28BYJ-48 & ULN2003 Combo. I did search online around to see if there is a readymade one available. when I couldnt find any exact matches, Just wrote this based on bits and pieces I found online. Hope you find it useful. Feel free create a issue or get in touch with me for any feature requests.

TODO : Insert pic here Fig: 28BYJ-48 & ULN2003 Combo

Here are two good links that helped me understand how to get the stepper working https://www.geeetech.com/wiki/index.php/Stepper_Motor_5V_4-Phase_5-Wire_%26_ULN2003_Driver_Board_for_Arduino http://chilipeppr2.blogspot.in/2016/10/controlling-byj48-stepper-motor-from.html

Download

since this is a single module file, I suggest raw file download for stepper.lua instead of a checkout. this is ment to be used in your project.

Usage

Connections

Any nodemcu gpio pins shoud work. here is the combination that worked for me.

NODEMCU	ULN2003
D5	IN1
D6	IN2
D7	IN3
D8	IN4

Compilation

THis is a big module. It takes a lot of your esp8266's precious memory. I suggest you compile this in to a .lc file to reduce memory consumption.

Loading module

load the lua module in your main program

stepper  = require ('stepper')

initailization

initialize the module with necessary variables parameters : table with 4 nodemcu pins that are connected to ULN2003, for exmaple, {5,6,7,8} is expected if uln2003 motor driver is connected as mentioned in Connections section.

pins = {5,6,7,8}
stepper.init(pins)

Rotation

Once the initalization is done, you can call rotate method like this. On successfull completion of given rotation the callback you passed as a last parameter will be invoked. Note : this is a async method. It'll trigger rotation and return immediately.

Signature :

rotate( direction, desired_steps, interval, timer_to_use, callback)

Parameters :

Parameter	Description
direction	stepper.FORWARD or stepper.REVERSE
desired_steps	number between 0 to infinity - 2500 is default which is roughly half a rotation
interval	time delay in milliseconds between steps, smaller self number is, faster the motor rotates . 5 is default
timer_to_use	which nodemcu timer to use, 0 is default
callback	_callback to invoke on completion of given rotation

Example :

direction = stepper.FORWARD 
desired_steps = 2500 
interval = 5 
timer_to_use = 0 
stepper.rotate(direction,desired_steps,interval,timer_to_use,function ()
    print('Rotation done. inside callback.')
    -- do some thing useful 
    end)

Full example

stepper  = require ('stepper')
stepper.init({5,6,7,8})
stepper.rotate(stepper.FORWARD,2500,5,0,function () print('Rotation done.') end)