3D printed part files can be seen on Thingiverse
Why I made this Project?
I made this project coz i feel there is so much of technology available but still there are many parts of the world where there is either not an awareness or lack of resources to make use technology that can be helpful to people. And disasters can happen anywhere. The application for this robot that i shared above is something that i have seen happening around me. So i thought of creating a solution. A cheap solution for everyone. i have named this rover Rakshak-one whch means Saviour
What this robot is capable of doing?
This robot can be controlled by sending commands from the GUI running on the laptop. For wireless transmission of command XBEE series 2 modules are used. The robot can go through different types of terrain,can go through special terrains like the stairs. The GUI software also processes the incoming data and displays it on the screen.
The rover has 3 onboard sensors namely LM35 temerature sensor, MQ2 gas sensor, Hall sensor. The rover gathers the temperature,gas,speed data and sends it back to the GUI. The software processes the incoming data and can also give voice alert if the value of smoke and other gases is above a preset value.The software also records the sensor value changes in a .csv file that can be used to plot the data. The GUI can also display video from a connected camera.
Block Diagram Of the System
Below is a simple block diagram that depicts the functionality of this robotic system.
The board numbered 1 is the first board on which i tested various motors . The IC used is L298 by STmicroelectronics. The board is a paper epoxy board designed on eagle and completely fabricated at home using the laser printer and hot iron method.Once i found it good i went for a more compact design that is numbered as 2 this is a glass epoxy board ,i ran two of my robots using this board.
I wanted to make a shield(A shield is an arduino compatible pin configuration) so that the hardware can be neatly stacked on the arduino uno .I came across a motor driver on an online shop and i found the design to be very compact. After running the motors of Rakshak-1 on it i understood that it is a overuse of resources and space to go with big power diodes IN5408 for blocking the spikes produced by motors rather a IN4007 would suffice and would make the design compact.
To make the system up and running i needed to have a hardware which can provide different voltages and can give enough power to drive the motors and power the sensors, micro-controller and other peripherals. Initially the GUI software is tested with the hardware arrangement numbered as 3. The shield was handwired and i have used a 11.1 v 1500mAh lithium ion battery to power the system. If you would look closely there are 4 resistors of quarter watt attached in parallel to drop the voltage from 11.1 to 9v This 9v is fed to the motors and 5v regulator provides power to arduino ,IC operations and LM35. Since i couldnot find a single resistor of high wattage adding 4 in parallel solved the wattage problem but still using resistors to drop voltage when current drawn is high is an inefficient method. Hence i decided to use a buck configuration in the next design of shield.
A coil is an integral part of a buck circuitry,but soon i realised that finding a coil of particular value is a uphill task ,i searched on element14 and a few other places but an exact coil was very hard to find ,moreover the price of coil was almost of the same price as that of a buck convertor module that include an IC ,some capacitors LED. So i initially though i will buy a module will desolder the coil and use it on the board i will design but there was another thing that was going to put me in a tight spot and that was the board house. The board house that i had easy access to still follows manual processes so i couldn't route the wires too close,too thin, moreover i have to use the locally available through hole components because the SMD components are harder to find locally and the vender wouldn't make something available to you until you order in bulk. So finally the most practical solution was to buy the buck converter module and use it as a component. So i designed the pads where i can fix the module. The only SMD component that i used are the LM1117 regulators which were not only small in size but can also provide current upto 800mA.
After all this came the design number 4 , i had to add a component externally and it worked but i missed a few design consideration as i designed it in a hurry. In the next design no 5 i fixed those things and finally got something good .
The Custom designed shield for Arduino Uno
The software on the onboard micro-controller turns on and turns off the geared DC motors ,headlights and set the position of servo motors depending upon the data received by the GUI. It also samples the temperature sensor and gas sensor data using its 10 bit successive approximation type ADC. It also measures the number of revolutions of motor by using a hardware setup which includes a hall effect sensor by allegro and a magnetic ring, the ring has 8 poles north and south places alternatively the ring is mounted on the output shaft of the motor when one of the two pole passes the output of the sensor turns high and when other one passes the output becomes low. These state changes are counted by the micro controller over a period of time using the interrupts and then are sent to the GUI to use this data to find out the RPM and distance by taking into account the Circumference of wheel. I have tried to keep the manipulation on the GUI side as the microcontroller is a low end 8 bit microcontroller working at just 16Mhz.
The GUI software is written using open source processing development environment. This GUI software can run on MAC, Windows or Linux.
The software is under documentation process.
3D PRINTING AND EN-CLOSER
3D printing is a great technology for makers In order to make place for my electronics i needed a housing . I wanted to design something that is simple and neat to keep all my electronics inside it save and intact.
Free Hand drawing of my designs
Designs after 3D printing
Video describing my thought process
A SHORT GLIMPSE OF ROBOT IN ACTION
This video depicts the movements that the rover can perform