L293D DC Motor Driver IC :
Purpose:
This article is intended for beginners whose project contains DC motors
that have power supply Voltage and Current rates higher than MCU
(microcontroller) can provide. It will also cover controlling rotation speed using PWM signal generated by microcontroller. For better understanding basic electricity knowledge needed (such as what is capacitor and DC voltage polarity). At the end of this tutorial reader should be able to use L293D motor driver in his project for controlling at least 2 DC motors.
For what motor driver is needed?
Usually microcontrollers are power supplied by low voltage power supply and in the meantime it's required to controll DC motors at the higher Power consumption rate than controller can provide, so not to burn out you microcontroller you will need an intermediate device to convert voltage levels and steer high current.
DC Motors - polarity/direction and PWM/speed
As we already know DC motors rotation direction depends on the polarity of its power supply(ex. +/- forward , -/+ backward). So if we can control polarity of power supplied applied to motor we'll be able to control rotation direction.
Simple way to make it is to use switchers like in the picture bellow.
PUSH-PULL FOUR CHANNEL DRIVER WITH DIODES
DESCRIPTION
L293D from Texas Instruments is designed to provide bidirectional current up to 600mA at voltages from 4,5V to 36V. It has two independent channels (it means can control 2 DC motors) that are designed to work in positive-supply
applications
The Device is a monolithic integrated high voltage, high current four channel driver designed to accept standard DTL or TTL logic levels and drive inductive loads (such as relays solenoids, DC and stepping motors) and switching power transistors. To simplify use as two bridges each pair of channels
is equipped with an enable input. A separate supply input is provided for the logic, allowing operation at a lower voltage and internal clamp diodes
are included. This device is suitable for use in switching applications
at frequencies up to 5 kHz. The L293D is assembled in a 16 lead plastic
package which has 4 center pins connected together and used for heatsinking
The L293DD is assembled in a 20 lead surface mount which has 8 center pins connected together and used for heatsinking.
Every data that you will ever need you will find in its datasheet. I will present you only summary data that is needed for a simply current flow direction control. L293D allows control of any load with currents not bigger than 600mA; this current can rise up to 1A in case of using heat-sink.
Channel 1
PIN 1 - enables channel 1 for steering first load (in our case 12V dc motor)
PIN 2, 7 - logical level input (can be from MCU any I/O port pin)
PIN 3, 6 - Power output 1 (here we are connecting 12V DC motor)
Channel 2
PIN 9 - enables channel 2 for steering first load (in our case 12V dc motor)
PIN 10, 15 - logical level input (can be from MCU any I/O port pin)
PIN 11, 14 - Power output 2 (here we are connecting 12V DC motor)
Power supply
PIN 8 - Power supply for logic part of our bridge. From 4,5V to 7V.
PIN 16 - Power supply for controlled load. From 4,5 to 36V and up to 600mA
PIN 4, 5, 12, 13 - Ground(-) and heat sink connection.
- l293d Motor driver ic
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