Different ics:- L293 Description The L293 and L293D are quadruple high- current half H- current half -H drivers. The L293 is designed to provide bidirectional drive current of up to 1 A at voltage from 4.5V to 36V. The L293D is designed to provide bidirectional drive current of up to 600-mA at voltage from 4.5V to 36V. Both devices are designed to drive inductive loads such as relays, solenoids, dc and bipolar stepping motors, as well as other high-current/high-voltage loads in positive- supply applications. All inputs are TTL compatible Each output is a complete totem-pole drive circuit, with a Darlington transistor sink and as pseudo- Darlington source. Drivers are enabled in pairs, with driver 1 and 2 enabled by 1,2EN and driver 3 and 4 enabled by 3,4EN. When an enabled input is high, the associated drivers are enabled and their outputs are active and in phase with their inputs. When the enable input is low, those drivers are disabling and their outputs are off and in the high- impedance state.
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Transcript
Different ics:-
L293
Description
The L293 and L293D are quadruple high- current half H- current half -H
drivers.
The L293 is designed to provide bidirectional drive current of up to 1 A
at voltage from 4.5V to 36V.
The L293D is designed to provide bidirectional drive current of up to
600-mA at voltage from 4.5V to 36V.
Both devices are designed to drive inductive loads such as relays,
solenoids, dc and bipolar stepping motors, as well as other high-current/high-
voltage loads in positive- supply applications.
All inputs are TTL compatible
Each output is a complete totem-pole drive circuit, with a Darlington
transistor sink and as pseudo-Darlington source.
Drivers are enabled in pairs, with driver 1 and 2 enabled by 1,2EN and
driver 3 and 4 enabled by 3,4EN.
When an enabled input is high, the associated drivers are enabled and
their outputs are active and in phase with their inputs.
When the enable input is low, those drivers are disabling and their
outputs are off and in the high-impedance state.
With the proper data inputs, each pair of drivers forms a full-H (or
bridge) reversible drive suitable for solenoid or motor application.
On the L293, external high –speed output clamp
ACKNOWLEDGEMENT
We take this opportuni ty to humbly express our thankfulness to a l l those
concerned with our project ent i t led l ine fol lowing robot using microcontrol ler .
We express very s incere thanks to Mr.D.M.MODI for providing us an opportuni ty
to works on such an interest ing project , wi thout whose help we could not have
completed pt sat isfactor i ly his invaluable guidance has proved to be a key tour
success pin overcoming chal lenges.
We faced during the course of the project work. We are a lso obl iged to
Mr.R.J .PATEL, HOD Electronics & Communicat ion department , for a l lowing us
to do project in this par t icular organizat ion. We are special thanks Mr.D.M.MODI
lecturer of the EC department for guide this project and good suggest ion.
Introduction
What is a line follower?
Line follower is a machine that can follow a path. The path can be visible like a black line on a white
surface (or vice-versa) or it can be invisible like a magnetic field.
Why build a line follower?
Sensing a line and maneuvering the robot to stay on course, while constantly correcting wrong moves
using feedback mechanism forms a simple yet effective closed loop system. As a programmer you get
an opportunity to ‘teach’ the robot how to follow the line thus giving it a human-like property of
responding to stimuli. Practical applications of a line follower: Automated cars running on roads with
embedded magnets; guidance system for industrial robots moving on shop floor etc.
Background:
I started with building a parallel port based robot which could be controlled manually by a keyboard.
On the robot side was an arrangement of relays connected to parallel port pins via opto-couplers.
The next version was a true computer controlled line follower. It had sensors connected to the status
pins of the parallel port. A program running on the computer polled the status register of the parallel
port hundreds of times every second and sent control signals accordingly through the data pins.
It’s difficult to control speed of motors. As cable length increases signal strength decreases and
latency increases. A long multi core cable for parallel data transfer is expensive. The robot is not
portable if you use a desktop PC. The obvious next step was to build an onboard control circuit; the
options a hardwired logic circuit or a uC. Since I had no knowledge of uC at that time, I implemented
a hardwired logic circuit using multiplexers. It basically mapped input from four sensors to four
outputs for the motor driver according to a truth table. Though it worked fine, it could show no
intelligence – like coming back on line after losing it, or doing something special when say the line
ended. To get around this problem and add some cool features, using a microcontroller was the best
option.
Algorithm:
1. L= leftmost sensor which reads 0; R= rightmost sensor which reads 0.
If no sensor on Left (or Right) is 0 then L (or R) equals 0;
Ex:
L4 L3 L2 L1 R1 R2 R3 R4
1 0 0 1 1 1 1 1
Left Center Right
Here L=3 R=0
L4 L3 L2 L1 R1 R2 R3 R4
1 1 0 0 0 0 0 0
Left Center Right
Here L=2 R=4
2. If all sensors read 1 go to step 3,
else,
If L>R Move Left
If L<R Move Right
If L=R Move Forward
Goto step 4
3. Move Clockwise if line was last seen on Right
Move Counter Clockwise if line was last seen on Left
Repeat step 3 till line is found.
4. Goto step 1.
Implementation
Sensor Circuit:
Description: These simple devices operate at 940nm and work well for generic IR systems
including remote control and touch-less object sensing. Using a simple ADC on any microcontroller
will allow variable readings to be collected from the detector. The emitter is driven up to 50mA with
a current limiting resistor as with any LED device. The detect is a NPN transistor that is biased by
incoming IR light.
Applications:
IR Schematic - Basic object detection schematic
Seattle Robotics - Infrared object detection
Robot Room - Excellent website with lots of goodies