The article explains how to make motor controller circuits using the IC L293 through different modes of operations, and by using as many as 4 motors with separate control facility.
In our previous post we studied the pinout and functioning details of the IC L293, here we learn how the same IC can be used for controlling motors through specific modes and configurations.
The IC L293 can be used for controlling motors in the following modes:
1) 4 motors through independent PWM inputs.
2) 2 Motors in a bidirectional or totem pole mode with speed control through PWM
3) One 2-phase BLDC motor using PWM input
The image below shows how the IC could be used for controlling motors with independent controls, and also how a single motor could be used for achieving a bidirectional control:
The left side of the IC shows a motor being configured to work in the bidirectional mode. To ensure that the motor spins in one of the selected directions, pin#1 and pin#7 must be applied with an anti-phase 5V DC input. To change the direction of the motor rotation, this 5V polarity could be changed across the mentioned input pinouts.
Pin#1 must be held at logic high in order to keep the motor and the IC functioning enabled, a logic 0 here will instantly stop the motor.
The supply at the control input pinouts could be in the form of a PWM, this could be additionally used for controlling the speed of the motor from 0 to maximum simply by varying the PWM duty cycle.
The right side of the IC depicts an arrangement wherein a couple of motors are controlled independently through independent PWM inputs at the respective pin#15 and pin#10.
Pin#9 must be held at logic high in order to keep the motor and the IC functioning. A logic zero at this pinout will instantly stop and disable the function of the attached motors.
Since the left side and the right side sections of the IC are identical with their pinout functioning details, the shown arrangement of the motors could be swapped across the relevant pinouts to achieve identical functioning as explained above, meaning two individual motors could be connected at the left side of the IC exactly as implemented at the right side of the IC in the diagram.
Similarly the bidirectional system could be incorporated at the right side of the IC pinouts exactly as achieved at the left side of the IC in the above shown diagram.
The above example shows how the IC L293 can be used for controlling 4 motors individually, or 2 motors in a bidirectional mode, and how the speed also can be controlled using a PWM feed at the relevant input pinouts of the IC.
Using L293 to control a 2-phase BLDC motor
In the above image we can see how the IC L293 can be configured to control a 2-phase BLDC motor using the indicated pinouts and through a couple of control inputs shown as control A and control B.
A single 2-phase motor can be seen connected across the outputs of the IC, while the inputs are wired with a set of NOT gates which become responsible for creating the required anti-phase input logic for the motor control.
Control A and Control B points may be subjected to an alternating logic for enabling the 2-phase motor to rotate correctly.
The polarity of the alternating logic decides the rotational direction of the motor.
For achieving a linear speed control on the motor, a PWM form of logic could be implemented across the control A and control B inputs and its duty cycle could be varied for achieving the desired speed control on the connected motor.