How can we rotate a DC motor in clockwise and anti clockwise directions? Or how can we rotate a motor in forward and reverse direction? These are the popular question asked by many of the robotic beginners. DC Motor (control) driver circuits are the essential circuit of robotics workshop. L293D IC is widely used for implementing DC motor control circuits. It is a dual H bridge motor driver IC, that is it can drive two DC motor simultaneously and is available in 16 pin DIP package. We have already posted H Bridge motor driver circuit with transistors. L293 driver IC has a current capacity of 600mA per channel and a wide supply voltage range (4.5 to 36V DC). They are integrated with internal high speed clamp diodes for inductive spike protection. Other superior features of L293 are high noise immunity, internal ESD protection, thermal shutdown and separate input supply for each channel.
Circuit diagram of L293 motor driver
Components required for DC motor driver
- Power supply
- L293 Motor driver IC
- DC Motor (5V, 250mA)
- Switches x 4 Resistors (1kΩ x 4)
Working L293 driver circuit
- To understand the working principle of L293 driver IC circuit you must read What is H bridge?
- L293 IC can drive two DC motors simultaneously. Each output has its own Enable pin (EA for Motor 1, EB for Motor 2).
- If EA or EB is zero (Low voltage), the corresponding DC motor is free to move on their shafts.
- After giving 1 (High voltage) to the Enable pin, we can control the direction of rotation of DC motors by digital manipulation of the inputs.
- For each motor there will be two inputs (for Motor 1, inputs are A1 and A2; similarly B1 and B2 for Motor 2).
- If both inputs are 0 or 1, the DC motor shaft is locked or baked.
- Alternate input combination will drive the motor in either direction.
- Please refer the below table, it shows the possible input combinations and the direction of each motor.
EA
|
A2
|
A1
|
Motor 1
|
EB
|
B2
|
B1
|
Motor 2
|
0
|
X
|
x
|
Shaft free
|
0
|
x
|
x
|
Shaft free
|
1
|
0
|
0
|
Shaft locked
|
1
|
0
|
0
|
Shaft locked
|
1
|
0
|
1
|
Clockwise
|
1
|
0
|
1
|
Clockwise
|
1
|
1
|
0
|
Anti-clockwise
|
1
|
1
|
0
|
Anti-clockwise
|
1
|
1
|
1
|
Shaft locked
|
1
|
1
|
1
|
Shaft locked
|
- In our circuit we applied A2=0, A1=1; B2=0, B1=1 using pull down resistor switch arrangement. Hence both motor will rotate in clockwise direction.
- You can make a simple robot with this driver circuit. It can move forward, backward, turn left and right. Keep in mind the maximum current capacity of L293D is 600mA, so don’t use DC motors that consumes more than 600mA current.
Pin out of L293
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