Using the L239D motor driver IC

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*
*Input* 1	*Input* 2	*Input* 3	*Input* 4	*Output* 1	*Output* 2	*Output* 3	*Output* 4	*Right*	*Left*	*Movement*
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