Group Assignment

This week group assignment was to design and make machine. our group i made by 9 participants and we have selected two machine types : one is Arm robot and other one is laser cutter machine.the group work is documented on FabLab Rwanda web page

My Contribution

My task was to make a study on needed stepper motor to be used for both cases , propose stepper motor available and make a stepper motor drive for both assignment.

Selected Stepper Motors to be used

in FabLab Rwanda , we have only NEMA 17 and NEMA23 stepper motors and we have to adopt to use them in our assignment. so i had to explore them with all their characteristics before making their controllers or drivers

NEMA17 AND NEMA23 SPECIFICATIONS

NEMA 17 Stepper Motor Technical Specifications

Specification	Value
Holding torque	40 N·cm
Step angle	1.8°
Current per phase	1.5 A
Resistance per phase	2.4 Ω
Inductance per phase	3.8 mH
Detent torque	2.2 N·cm
Rotor inertia	34 g·cm²
Weight	0.28 kg
Length	47 mm

NEMA 23 Stepper Motor Technical Specifications

Specification	Value
Holding torque	120 N·cm
Step angle	1.8°
Current per phase	2.8 A
Resistance per phase	0.9 Ω
Inductance per phase	2.5 mH
Detent torque	5.5 N·cm
Rotor inertia	480 g·cm²
Weight	1.2 kg
Length	76 mm

From the laser design we did in solidworks , we decided to use TWO NEMA 23 ON X axis because the have used heavy MDF material without best fixing techniques which can cause mis-allignment in x-axix movement, so we decided to use two nema17 stepper motors on x-axis to be sycnhronized togather

Our Design

For Y axix , we decided to use NEMA17 becuse the laser Head is not heavier

Design Stepper motor driver

I had to look around and find the available stepper motor driver chip mostly used and available to our local store and i found ony A4988 stepper motor driver and drv8824 driver . the following are their specifications

A4988 vs DRV8824 Stepper Motor Driver Comparison

Specification	A4988	DRV8824 >
Maximum current	2 A	2.5 A
Maximum microstep resolution	1/16	1/32
Input voltage range	8 - 35 V	8.2 - 45 V
Output voltage range	Same as input voltage	Same as input voltage
Logic voltage	5 V	3.3 V or 5 V
Number of stepper motors	1	1
Thermal shutdown protection	Yes	Yes
Over-current protection	Yes	Yes
Adjustable current limiting	Yes	Yes
Dimensions	20 mm x 15.5 mm x 10 mm	20 mm x 15.5 mm x 5.5 mm

From the power perspective, both A4988 and drv8824 , produce current lower that 2.5 A where NMA 23 CONSUMES 2.7 a PER PAHSE. here we have used NEMA17 for A4988 because it is what we have .

for NEMA23 , we suggested the use of coomercial drivers like TB6600

TB600 stepper motor specification

Parameter	Specification
Input Voltage	DC 9-40V
Output Current	0.2A - 5A
Microstep Resolution	1, 2, 4, 8, 16, 32
Pulse Frequency	0-20kHz
Overheat Protection	Yes
Short Circuit Protection	Yes
Dimensions	96 x 56 x 33 mm

This driver can provide up to 5A which is adequate current for our NEMA23 stepper driver

Microcontroller Connection For TB6600 STEPPER MOTOR DRIVER

Team member working on different tasks

Designing Motor Controller for Our Arm robot

The arm robot will use only NEMA17 stepper motors so i had to desifn the driver board based on A4988 DRIVER in order to controll the robot movement

Making of Stepper Motor control Board

To be able to control stepper motors, motor control board is needed . we made a control board based on A4988 stepper motor drive BOARD

Testing the Soldered stepper Motor Driver on NEMA17 Stepper motors

we have flashed GRBL Firware in Atmega328 mcu we send g-code from PC to the MCU and the stepper motor starts providing the current to the motors

The rest of the work was to assemle