From microcontroller
we can not connect a motor directly
because microcontroller can not give sufficient current to drive the DC motors. Motor driver is a current enhancing device, it can also be act as Switching Device.
Thus we insert
motor driver in between
motor and microcontroller.
Motor driver take the input signals from microcontroller and
generate corresponding output for motor.
Motor Driver IC L293D
This is a motor driver IC that
can drive two motor simultaneously. L293D IC is a dual H-bridge motor driver IC. One H-bridge is capable to drive a dc motor in bidirectional. L293D IC is a current enhancing IC as the output from the sensor is not able to drive motors itself so L293D is used for this purpose. L293D is a 16 pin IC having two enables pins which should always be remain high to enable both the H-bridges. L293B is another IC of L293 series having
1. L293D can run a motor up to 600 mA whereas L293B can run up to 1 A.
2. L293D has protection diode whereas L293B doesn’t have any such protection diode. Need to
add the protection diode manually.
Connecting L239D to motors
Diagram 2
Points regarding L293D
Supply voltage
(Vss) is the Voltage at which we wish to drive the motor.
Generally we prefer 6V for dc motor and 6 to 12V for gear motor, depending
upon the rating
of the motor.
Logical Supply Voltage
will decide what value of input voltage
should be
considered as high or low .So if we set Logical Supply Voltage equals to +5V, then
-0.3V to 1.5V will be considered as Input Low Voltage and 2.3 V to 5V will be considered as Input High Voltage.
L293D has 2 Channels .One channel is used
for one motor.
• Channel 1 - Pin 1to 8
• Channel 2 - Pin 9 to 16
Enable Pin is use to enable or to make a channel active .Enable
pin is also called as Chip Inhibit
Pin.
All Input (Pin No. 2, 7,10and 15) of L293D
IC
is
the
output
from
microcontroller (ATmega8).
E.g.-We connected (Pin No. 2, 7, 10 and 15) of L293D IC to (Pin No. 14,
15,16and 17) of ATmega8 respectively in our robots, because on pin 15
and 16 of ATmega8 we can generate
PWM.
All Output (Pin No. 3, 6,11and 14) of L293D IC goes to the input of Right and
Leftmotor.
if Enable pin low, the output will
be at 0 always. If its high output depend
on input
Output Connections
• OUTPUT 1 (Pin No 3) ---
Negative Terminal of Right Motor
• OUTPUT 2 (Pin No 6) --- Positive Terminal of Right Motor
• OUTPUT 3 (Pin No 10)
---
Positive Terminal of Left Motor
• OUTPUT 4 (Pin No 14)
---
Negative Terminal of Left Motor
Input
1
|
Input
2
|
Input
3
|
Input
4
|
Output
1
|
Output
2
|
Output
3
|
Output
4
|
Motors Output
|
Movement
|
|
Right
|
Left
|
|||||||||
Low
|
High
|
High
|
Low
|
0
|
Vss
|
Vss
|
0
|
Straight
|
Straight
|
Straight
|
Low
|
High
|
Low
|
Low
|
0
|
Vss
|
0
|
0
|
Straight
|
No move
|
Left
Turn
|
Low
|
Low
|
High
|
Low
|
0
|
0
|
Vss
|
0
|
No move
|
Straight
|
Right Turn
|
Low
|
High
|
Low
|
High
|
0
|
Vss
|
0
|
Vss
|
Straight
|
Reverse
|
Sharp Left
|
High
|
Low
|
High
|
Low
|
Vss
|
0
|
Vss
|
0
|
Reverse
|
Straight
|
Sharp Right
|
High
|
Low
|
Low
|
High
|
Vss
|
0
|
0
|
Vss
|
Reverse
|
Reverse
|
Backward
|
