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• Motors Arrived + Sketching in SketchUp

  ZaidPirwani • 07/16/2016 at 19:47 • 0 comments

  so, the guy working on SolidWorks model is on leave and I couldn't wait for him to return to finish the model. Started making a simpler model in SketchUp just to figure out the sizing, shape and wiring and such.

  Same sensor PCB on all sides of the Octagon.

  I also got the motors, they are supposed to be for a self-balancing robot kit - wont be making that, but the desire to make that is strong.

• Wheels and Wheeeeeeels

  ZaidPirwani • 07/11/2016 at 19:46 • 0 comments

  After selecting motors, getting the motor drivers made, sensor PCbs and other stuff, came the task of getting or making the wheels, this has been one of the hardest thigns to do while making a robot as in Karachi - you cant just go to the radioshack (there isnt one) and buy wheels of the requried diameter/shaft measure etc. Nor is importing/buying form the online stores feasible.

  Luckily, I found this: http://www.thingiverse.com/thing:21486 the

  Highly Configurable Wheel (One Wheel To Rule Them All)

  Explanation Link: http://www.thefrankes.com/wp/?p=2674

  
  This introduced me to the world of OpenSCAD and cause I recently had setup my 3D printer (have a prusai3 and a Solidoodle 4), it took no time, actually about an hour to get the first wheel printed.

  Bought o-rings from the local market and the wheels are ready - I also tried these wheels on a smaller LFR robot.
  

  
  

  the small Line Follower Robot (without the sensors, but 3d printed wheels)
  

• Arduino Nano Sensor PCB Shield

  ZaidPirwani • 07/10/2016 at 04:48 • 0 comments

  Made a shield, or sort of shield for reading all the sensors on the sides, plan is to use an Arduino Nano to read all the sensors and it would do the filtering etc needed and just keep printing out sensor values comma separated on Serial which will be then read by some other controller..

  To connect all the sensors to the Arduino Nano, designed a shield for the Nano.

  Total number of pins needed

  • 1x Analog Pin for IR Sensor RX - TCRT5000L
  • 1x Digital Pin for IR Sensor TX - TCRT5000L
  • 1x Digital Pin for Echo Pin on Sonar Sensor - HC-SR04
  • 1x Digital Pin for Trig Pin on Sonar Sensor - HC-SR04

  This is 1 Analog and 3 Digital pins per sensor baord and I have 8, so 8 Analog pins and 24 Digital pins, Arduino Nano does not have enough Digital Pins, luckily recently I hade bought a batch of MCP23017 GPIO Multiplexer IC, which has 16 pins and also luckily Arduino Nnao has 8 Analog input pins, (unline Arduino Uno, which has only 6 analog input pins).

  Same drill, a PCB was made working on my sketches and sent to Seeed Fusion PCB Service.

  The Git Repo Link for the PCB Eagle files: https://github.com/zaidpirwani/CONTROLLER_sensor-board_Eagle

• Sensor Skirt for Mapping/Obstacle Avoidance

  ZaidPirwani • 07/10/2016 at 04:30 • 0 comments

  So, just as Khepera has an array of sensors distributed evenly across its outsie, I wanted something similar, as my design is an OCTAGON for the robot, I thought, maybe just put in 8 sensors max.

  The sensors need to do basic RANGE/DISTANCE measurement, which can easily be done with cheap Ultrasonic Sonar sensor modules HC-SR04, but the sonar sensors cannot reliably detect obstacles which are too close, so I also added IR proximity sensors on each side.

  Decided to make a small PCB strip for each side, which would have the sonar sensor and the IR sensor fixed to the acrylic wall/side of the octagon. So, even if I dont want to use Sonar on all sides, at least all sides will have IR sensors.

  The IR sensor TX LEDs are individually controllable by a digital IO pin, so that the ambient light measurement and reflective light measurement both can be done.

  Same as the H-Bridge, had [Maaz Mobin] made a schematic and PCB from my rough sketches and then have sent the designs to Seeed Fusion PCB Service, hopefully will get the PCBs in the next 10 days.
  

  
  

  Git Repo link for the sensor PCB: https://github.com/zaidpirwani/musafir_sensor-board__-Eagle

  The PCB has a jumper as well, which can be shorted and the IR TX LED will remain ON.

• H-Bridge Schematic and PCB Design

  ZaidPirwani • 07/09/2016 at 10:08 • 0 comments

  So far, in all my robotics projects, I have been happy with just using L293D IC and the L298 IC or modules which use these ICs.

  But, this time, wanted to make an H-Bridge module using MOSFETs and wanted to get a PCB.

  Yet again, a student of mine who was really really interested in working alongside with me and he too had an interest in Robotics, so we sat down a couple of days and I had him working with EagleCAD and GIT and get a simple schematic and a 2 layer PCB made.

  Using mostly Seeed OPL components and made the PCB with design rules from Seeed Fusion PCB Service.

  I did most of the cosmetics type work on the final PCB form Maaz and now this has been sent to Seeed, hoping to get this in the next 10 days.

  Git Repo Link: https://github.com/zaidpirwani/H-Bridge-IR2104_IRF540

• CAD Model - a START

  ZaidPirwani • 07/09/2016 at 10:01 • 0 comments

  So, I had recently met with a student at PAF KIET who is currently in his 3rd semester of BE, interesting in doing some CAD work to practice. So, I had him sit with me and work on a model in SolidWorks - that is what is taught at the university.

  I also introduced him to GIT and told him to commit his work as often as possible, but looks like he has not committed the latest edits, but here is the repo and the current repo variant is something of a basic base design, without the wheels or anything.

  used https://a360.autodesk.com/viewer/ to generate some snaps, as I myself dont have SolidWorks installed on my laptop.

  
  

  The repo Gighub link is: https://github.com/zaidpirwani/musafir-CAD/

• Rough Sketches and Ramblings on Paper

  ZaidPirwani • 07/09/2016 at 09:55 • 0 comments

  So, I do most of my work sketching things on paper and basically thinking out loud, just on paper with a pencil.

  So, these are some images of the sheets that have survived so far in the project, mainly uploading here for my own record, as I know I will lose these sheets. I have used these sheets to get a basic CAD model made by a student/intern of mine. :)

• Dimensions

  ZaidPirwani • 07/09/2016 at 09:39 • 0 comments

  So, these are the Khepera IV dimensions

  But, making the bot circular would be a challenge, so going for an OCTAGON-al design.

  All Laser Cut acrylic sheets, 5mm maybe. The Khepera Diameter is 140mm or 14cm, we cannot go that small as the motors are bigger and as I have come to know that a robot is made AROUND a motor, so whatever the motor size is, that dictates the robot size.

  So, motor specs.

  the Grearbox is about 30mm on its own, so only 2 motors side by side is 70mm, then add wheels and space for sensors, so possibly the robot will go about 200mm form side to side.

  Off to making rough designs and drafts on paper and then starting CAD and electronics work.

• More on Project Specifications and a wishlist

  ZaidPirwani • 07/09/2016 at 09:25 • 0 comments

  A detailed specification list of the project needs to be written, but so far, have arrived at this much.

  • 12V DC Geared Motors with Encoders for Differential Drive
    buying from China, AliExpress
  • Lipo Battery, 14.8V 4S 2500mAH or more
    buying from China, AliExpress
    
  • Motor Driver - MOSFET Based
    
  • UltraSonic Sonar Sensor HC-SR04 for Range/Distance measurement
    min. 4, maybe 8 max. distributed on sides
  • IR Proximity sensor - TCRT5000
    4 to 8 distributed on sides
  • GY-9150 IMU Sensor
  • NRF24L01+ Wireless Module
    
  • Arduino Nano to read all the Sonar and IR sensors
  • Arduino Mega as main Controller

  A little WishList of things that would be good if implemented.

  WishList

  • ROS Drivers
  • Raspberry Pi on board
    for WiFi, Bluetooth, Camera interfacing
  • 3D Simulation Model, for V-Rep Software
  • SLAM implementation
  • Kinect Expansion, if Raspberry Pi is attached

• Defining Project Specifications

  ZaidPirwani • 07/09/2016 at 08:16 • 0 comments

  So, first things first, study the available robotic platforms, Khepera and e-Puck and determine what are the desired goals and then define specifications.

  Khepera Specs are awesome, looking at the latest Khepera IV variant, small in size, camera, IR and sonar sensors, encoders, arm extension, RGB lights on top and simulation in V-Rep and WeBots and other software - COST is about 3500USD if I remember correctly.

  I wanted to make a robot within 350USD - the bare material costs, software costs not counted for.

  Minimum Robot Specifications

  • IR/Sonar sensor skirt around the bot
  • Round/Circular design
  • Differential Drive
  • IMU (Gyro + Accelerometer) + Compass Sensor
  • Wireless Communication
  • Encoders
  • Re-Chargeable Battery

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