Enabling a Theme on Ubuntu

Personally I love dark themes. You Know it is always easy and comfortable to work with a dark high contrast environment in a computer, for a developer. In Ubuntu, you can use Dark themes for this purpose. In order to install a theme, you have to install "Unity Tweak Tool" first from Ubuntu Software Center or runiing following command on your terminal

 sudo apt-get install unity-tweak-tool

In this article you can find a list of themes and commands for install them. following commands are for installing Ambiance-Dark theme.

1. sudo add-apt-repository ppa:noobslab/themes

2. sudo apt-get update

3. sudo apt-get install ambiance-dark

But after executing first command if you are getting an error as following screenshot, most probably you are using a proxy server.

There are two ways to get rid of this issue

The lazy mans way

1. Connect to a non proxy network, you can use a dongle or any other none proxy connection to this.
2. Run the first command.
3. If you have no data usage problems, run remaining two commands in while you connected to the same network, Otherwise connect again to the proxy network and run the remaining two commands.

The real way

In this this article you can find the real way.

I use my University's free wifi network which uses a proxy server whenever it is possible because I have a limited data quota in my mobile broadband package. Using any method mentioned above, you can save your data and your money.

Enjoy....

The Line Follower

A Ball Picking Robot Using PIC 16F877A

Actually this project was a group project. Our task was to build a line following ball-picking robot while keeping the budget below 5000 rupees. If you consider the cost for the parts, it wont exceed that limit. But , for testing and rebuilding it would cost more than that.

Details of the track and  capabilities of the robot

• The robot was expected to operate on an MDF board, approximately 7 ft long and 3.5 ft
wide.
• The surface of the board was painted in black, and a white curvy line (about 2” wide)
was drawn against the black surface.
• A tennis ball was placed at one end of the line and there was a hole at the other end.
An obstacle was placed somewhere on the line.
• Robot was  placed on the white line, near the end where the ball was placed. It moved towards the ball, detected it and grabbed it.
• Then it moved along the line towards the hole, avoided the obstacle, detected the hole
and droped the ball into it.
• The robot was fully autonomous .

Following figure give you more details about the track.

Design and Implementation

We have designed a circuit using Proteus. Our first board was not very successful but the second one was very.

circuit diagram

Printed Circuit Board Layout

Power Supply
We separated a used laptop battery cells and used 6 of them for the power supply . The whole robot was powered by these batteries

Sensor Circuit

The purpose of the sensor circuit is to identify the path that should be followed. 8 IR sensors (FGK 125) were used in the sensor panel but at the time of demonstration only 4 sensors were in a working condition. We have used another 8 IR LEDs to increase the IR signal.

  The black colour absorbs the IR and white colour reflects it. So when it identifies higher amount of IR it tends to follow the current path. When the robot senses a lesser degree of IR it deviates from that path to the previous one.

Motor Control Unit

The motors of the wheel are controlled by the on-board motor control unit.

We designed a separate circuit for driving the ball picking unit. It is shown below. All motors are driven by L 293-D Motor driver IC.

The circuit diagram of Motor driver of the ball picking unit

The Printed Circuit Board layour of Motor driver of the ball picking unit

Obstacle Detecting Mechanism
 We have used Sonar sensor to detect the tennis ball and the obstacle. We used a simple switch to detect the whole

Item	Quantity
Pic16F877A	1
180rpm Gear motor with wheel	2
7805 regulator	2
LM324 IC	2
L293 motor driver	2
In4001 diodes	8
50k pre-set	9
Vero board	1
Circuit wire	5m
Castor wheel	2
IR sensor with IR LED	8
IR LED	8
Sonar Sensor	1
Small motor(30/=)	1
1.5 Li Ion Laptop batteries	6

The Final Outcome

At the final demonstration the ball picking unit did not work. But i followed the line smoothly. The reason for the fault of the ball picking unit was the L293 motor driver. It was burned. This is a picture of the cutie. You may feel ugly... :D but she is beautiful for me.