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JARA (J
ust Another Robotic Arm)

     

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Overview
Components
Details
Circuit
Videos

 

Overview

The idea behind the JARA project was to introduce my students to a basic application of robotics by developing a 6DOF (Six Degrees Of Freedom) robotic arm from scratch.

For this project, considering the input/output requirements, the adopted control board was the Arduino MEGA (2560 REV3), which offers 54 digital input/output pins, 15 of which can be used as Pulse-Width Modulation (PWM) outputs, 16 analog inputs, and 4 Universal Asynchronous Receiver-Transmitter (UART) ports.

In addition, connected to this board, we have a MicroSD memory card reader to store information when the device is powered off, a pressure sensor RP-C10-ST (with a range from 20g to 2Kg) positioned on the jaw to calibrate gripping force, a DC-DC converter Arceli-AA0003 that allows us to use a single power source for the 6 motors (that approximately required 7 volts), and the board (that required 5 volts).

The choice of servo motors was oriented towards the Longruner LDX 218 model, which uses metal gears that offer good torque (max torque 17kg x cm) and are controlled through PWM signals.

After the prototyping phase, where the connections were made using jumper wires with Dupont connectors, the final connections to the board were made using an Arduino shield that allows the use of screw terminals for each board pin.

An I2C LCD1602 display (2 lines of 16 characters) was used to show relevant information during device operation.

The main unit that contains the board was placed inside an aluminum box for electronic assemblies, on the front panel of which necessary holes and labels were created (the labels were made using LibreCAD, an open source CAD software, printing them on a self-adhesive transparent sheet).

A second plastic box was used to assemble the control unit, which provides 2 dual-axis joysticks (QM070905), 2 micro-buttons (normal open) , and a micro-switch (deviator) that allow us to perform all possible motor movements, as well as record them and regulate the servomotor movement speed.

The two units and the arm were interconnected using 8-pin metal plug connectors (AC 200V 5A 16mm 8 pins female and male aviation connector plug), and power is supplied through a 12-volt, 5-ampere power supply.

A relevant part of the project was the assembly of mechanical parts, where, in addition to ensuring the stability and range of motion of each motor, the balancing of the arm's joints had to be considered.

Counterweights and springs were used to counteract unwanted movements when the motors were not powered.

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Components
1 x Arduino Mega 2560 REV3
1 x SPI Reader Micro Memory SD/TF Memory Card Module
1 x Arceli AA0003 DC-DC Converter
1 x AZDelivery HD44780 16x2 LCD
1 x Pressure Sensor YWBL-WH
9 x Normally Open (NO) Push Buttons
1 x Arceli Prototype Shield
2 x 3mm LED
2 x LED Holder for 3mm LEDs
1 x Microswitch Diverter (3 pins, 2 positions)
1 x Microswitch Momentary Diverter (3 pins, 3 positions)
1 x Potentiometer 10K Ohm
1 x Potentiometer Knob Cap
1 x DC Power Female Plug Jack Connector 2.5 x 5.5 mm
2 x DC Power Male Plug Jack Connector 2.5 x 5.5 mm
4 x GX16 Thread 8 Pin Female/Male Panel Metal Aviation Wire Connector 5A 18.6 x 11.2 x 2.2 cm
1 x StarTech.com USBAB2MR USB 2.0 A to Left Angle B Cable Cord
4 x Longruner LDX-218 Full Metal Gear Digital Servo Motor with 17kg High Torque Dual Ball Bearing (Range 180 degrees)
2 x AZDelivery MG995 Metal Gear Digital Servo Motor (Range 180 degrees)
2 x Metal Servo Arm 25T Disc Metal Horns for MG995 Servo Motor
7 x U-Type Mounting Case LQY10 for LDX-218 Servo Motor
1 x Aluminum box 54 x 204 x 120 mm
1 x Plastic box 200 x 110 x 55 mm
1 x Aluminum Arm Rotating Base for MG995 Servo Motor
1 x Aluminum Robot Clamp for MG995 Servo Motor
1 x Junction Box 3-Way Y-Type for Cable Diameters from 4 to 15 mm
1 x Expandable Braided Sleeving 10 mm, 3.1 m for electric wires
2 x 5-Pins Joystick
1 x Roll of Multi-Color Electric Wire, 0.5 mm Diameter
1 x Power Supply 12 Volt, 5 Ampere
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Circuit
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Details
Arduino Mega 2560 REV3: It is a microcontroller board based on the ATmega2560. It provides 54 digital input/output pins, with 15 of them capable of functioning as PWM outputs. Additionally, it offers 16 analog inputs, 4 Universal Asynchronous Receiver-Transmitter (UART) serial ports, a 16 MHz crystal oscillator, a USB connection, a power supply input jack, a reset button, and an In-Circuit Serial Programming (ICSP) header.

SPI Reader Micro Memory SD/TF Memory Card Module: This module enables communication between the microcontroller and an SD or TF memory card using the Serial Peripheral Interface (SPI) protocol.

Arceli ‎AA0003 DC-DC Converter: An adjustable DC-DC converter module that provides a stable power supply. It accepts input voltages ranging from 4 to 38 Volts and outputs voltages from 1.25 to 35 Volts, with a maximum output current of 3 Amperes. It features an LED display.

AZDelivery LCD1602 16x2 LCD: This display allows for the presentation of two lines of 16 ASCII characters and uses the I2C protocol for communication.

Arceli Prototype Shield: A prototype screw/terminal shield board designed for the Arduino Mega 2560 REV3. It offers a screw terminal for each pin on the board.

Pressure Sensor YWBL-WH: This sensor has a range from 20 grams to 2 kilograms and is a high-precision, resistance-type, thin-film pressure force sensor.

 
Videos

[Video #1]

At low speed, it picks up a container with a metal sphere from one position and places the sphere into another container, then repositions the container back to its original position.

[Video #2]

At moderate speed, it picks up a container with a metal sphere from one position and places the sphere into another container, then repositions the container back to its original position.

[Video #3]

At a moderate speed, it takes an object and places it in another location, then retrieves it and repositions it back to the exact starting position.

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Roberto Saia  -  All Rights Reserved