Saturday, January 21, 2012

Simple Beam Follower Robot

Beam Follower Robot

This is my second post, If you are looking for chassis construction and choosing motors  you can refer my previous post.Similar chassis can be used for building this robot too.I will be explaining a simple method to construct a beam follower robot by using minimum number of components.

Components required are as follows:

2 PRESET's 10K
2 zener diodes 1N4148.

1.The BC547 NPN Bipolar Junction Transistor (BJT) is designed to operate as the voltage gainer amplifier; this means we operate the BC547 transistor in its linear region.

2.The preset is use to adjust the DC motor speed. The key of using this circuit successfully is dependent on the DC motor choice. 

3.Two motors of 60 rpm each are used and right and left wheels are connected to each of these separately. Two Lars are connected at the front of the chassis.

4.Depending upon the intensity of light flashed on the LDRs,the motors will run at a specific speed. These LDRs are connected to the base of the transistors, the output of which is fed to the DC motors.

The circuit diagram is given below:

The same circuit is used for driving both motors.Two transistors are used in darling ton configuration for higher current gain providing more power for the motors.Depending on the intensity the robot will turn towards a particular direction.

A beam follower robot can also be constructed by using the following circuit, it will be little bit expensive but will provide a high efficiency.

The components required are:

Small DC motors – 2
IC1 74HC240 with base – 1
Photodiodes – 2
0.22uF capacitor – 2 
1K resistor – 1
3mm LED – 1
Small switch PTON/PTOFF – 1
Small prototyping PCB
AAA Cells – 4

Connect the components according to the circuit given and your beam-bot is ready.

Wednesday, January 11, 2012

My First Robot - Line Follower Without a Microcontroller

Line Follower Without Microcontroller

As the title says this blog is about how to build a simple Line Follower Robot Without using a Microcontroller.A lot of Engineering students in the 2nd/3rd semester are interested to build small robots, but unfortunately due to lack of  knowledge of Microcontrollers or programming they are unable to do so. This blog is to help all those interested engineering students and young robotic hobbies't to build simple robots.I will also make an attempt to give all the websites possible where you will be able to buy robotic components/ chassis material in India.

Building the chassis

well, the 1st step of building robots is to make the chassis.A lot of options are available to build a solid and low cost chassis.Ill write down all, choose the one that best suites you.

1.)Those who can spend a little bit of money and want good aesthetics for that robot can go for this option.This is a ready made metal chassis available at Robokits-India -->
The good thing about this chassis is that the clamps for fitting motors r attached to the body.So you can directly attach the motors to the body without any problem.But only problem is cost, i think 180/- is little bit on the higher side.

2.)The second option is, make the chassis yourself, well this is very simple but little bit time consuming task. Take a "Electrical board" commonly called as "sunmica" which is used to fix the household switches and current indicators in your homes.You will be able to find it easily at any electrical shop and hardly costs 15-20 bucks.

Ok, so next task is to drill holes to fix the motor clamps ,sensors, castor wheel.You can buy the motor clamp from Robokits
Drill 4 holes at the back each on the left and right side of the electrical board as shown.
castor wheel is a free moving wheel which is to be attached at the front of the chassis, so there will be 2 driving wheels at the back and a castor wheel in the front.You can buy castor wheel from robokits.Make sure you drill 3 holes in the front to fix the castor wheel.

The motor clamps and the castor wheel can be fixed to the electrical board by using nut and bolts.

If you have used the matal chassis will look something like this

Chassis made up of electrical board.

Please note: just look at the chassis construction neglect the electronics which is on the top.

Choosing the motors:
Well for applications such as simple line following it is always better to go for 60RPM motors, They r not that slow and if u go for higher RPM motors your robot might miss the line and it may be difficult to control the motion. So buy 60 RPM motors again ROBOKITS

With this the chassis construction is complete make sure u drill two holes somewhere in the middle to fix the line sensors.Lets go to the Electronics Part.

well the Electronics and sensor making is not that difficult to understand and to construct.Ill try my best to explain each and every component used and operation of the circuitry.
You can choose to assemble the circuitry either on the breadboard or solder it on to a vero board. But if this is your 1st robot and you hv never soldered before go for the bread board option.the circuit diagram is given below.
The components required are as follows.

2 white LED's , 3 220ohm resistors , 2 10k potentiometers(presets) ,2 LDR's, 2 zener diodes 1N4148, 2 transistors either 2N3904 or even BC547 will work , A 9V battery and 1 green LED. Entire cost will be less than Rs.70.

The circuit operation is explained below.
This is a Black line follower Robot circuit so your bot will follow a black line on a white background.When the bot is on the black line, light from the LED will not be reflected from the black surface and will not fall on to the LDR as a result the LDR resistance will be high and the transistor will be off. When transistor is in off condition the voltage at the collector is high since one end of the motor is already connected directly to battery , both points of the motor will be at the same voltage and the motor will not run.whereas when the bot is on the white line , light from the LED will be reflected on to the LDR, its resistance will decrease and the transistor will be switched on.When transistor is on the voltage at the collector is low ans as a result the motor will start running.If you want your bot to follow a white line simple interchange the motor connections i.e. connect right side motor to left transistor and vice verse.The transistor is used simply as a switch and not as a amplifier so it operates in the cut-off and saturation region and not in the linear region.

BC-547 transistor gives a faster response compared to 2N3904.The zener diodes 1N4048 are extremely important and have to be connected as their function is to protect the transistor circuitry from the back EMF effects of the motor.Just take care of the pin connection of the transistor BC-547 and 2N3904 have opp. pin connection.

This robot will follow the line effectively and will also be able to take sharp turns, but the speed will be little less due to use of Transistor circuitry whose response is little bit slow. Also this Robot will not be able to take smart decisions such as when the bot encounters a junction or a cluster of lines because there is no intelligence provided. How to build robots using Microcontrollers will be covered in my next posts. 

So, Go ahead start building your first robot. All the best!!!!
Fell free to post your queries ill make sure i answer them all.

I would like to thank Abhijeet, Nikhil, Noah and Pranav who started Robotics club in my college and took efforts to develop interest in robotics among the students from my college.