Motor driver L293d
L293D is a Motor driver integrated circuit which is used to drive DC motors rotating in either direction. It is a 16-pin IC which can control a set of two DC motors simultaneously. The L293D uses 5V for its own power and external power source is needed to drive the motors, which can be up to 36V and draw up to 600mA.
Concept[edit]
The L293D works on the concept of typical H-bridge, a circuit which allows the high voltage to be flown in either direction. In a single L293D IC there are two H-bridge circuits which can rotate two DC motors independently. Due to its size and voltage requirement, it is frequently used in robotics applications for controlling DC motors, including in Arduino projects. The L293D is also a key component in larger 'motor driver' boards available premade for hobbyists.
Working of L293D[edit]
There are two drive pins on L293D. Pin 1 (left H-bridge) and pin 9 (right H-bridge). To turn ON the corresponding motor, pin 1 or 9 need to be set to HIGH. If either pin 1 or pin 9 goes low then the motor in the corresponding section will go OFF (high impedance). These inputs (1 and 9) are the ones that should be used to control motor START/STOP and motor speed under PWM, since there would be high impedance output during low semiperiod of PWM, it would not provoke overload of the L293D when the motor is turning. Thus, PWM or motor ON/OFF control should never be input to pins 2, 7, 15, 10, which should only be used to control direction (Clockwise - CounterClockwise).
The direction-defining four Input pins for the L293D are pin 2 and 7 on the left and pin 15 and 10 on the right as shown on the pin diagram. Left input pins will determine the rotation of motor connected on the left side and right input for motor on the right hand side. The motors are rotated on the basis of the inputs provided at the input pins as LOGIC 1 or LOGIC 0.
L293D Logic Table[edit]
Assuming a motor connected on left side output pins (pin 3,6).
- Pin 2 = Logic 1 and Pin 7 = Logic 0 | Clockwise Direction
- Pin 2 = Logic 0 and Pin 7 = Logic 1 | Anticlockwise Direction
- Pin 2 = Logic 0 and Pin 7 = Logic 0 | Brake (this is not high impedance) (force stop rotation using electric brake = same voltage both pins of the motor = overload while the motor is still running)
- Pin 2 = Logic 1 and Pin 7 = Logic 1 | Brake (this is not high impedance) (force stop rotation using electric brake = same voltage both pins of the motor = overload while the motor is still running)
In a similar way, the motor can be operated across input pins 15 and 10 to control the direction of the motor attached to the H-bridge's right side. Using pins 2 and 7 ( 15 and 10) to determine motor START/STOP or PWM duties it's dangerous, since there wouldn't be high impedance outputs: Current would flow back during the low semiperiod of PWM when the motor is turning. For on/off purposes or PWM speed control , pins 1 and 9 should be used.
Voltage Specifications[edit]
The voltage (Vcc) needed for its own working is 5V but L293d will not use that Voltage to drive DC Motors. That means you should provide that voltage (36V maximum) to drive the motors. A maximum current of 600mA per output is allowed.
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