To control the robot’s motors need a device that would have transformed the control signals of low power in the currents that are sufficient to control the motors. Such a device called the motor driver .
There are many various schemes for motor control. They differ in how capacity and element basis on which they are made. We will focus on the simplest driver motor control, performed in a completely ready for operation in the chip. This chip is called the L293D is one of the most popular chips intended for this purpose.
L293D contains just two drivers to control the motors of low power (four independent channels, combined in two pairs). It has two sets of inputs for control signals and two pairs of outputs for connecting electric motors. In addition, the L293D has two entrances to the inclusion of each of the drivers. These inputs are used to control the speed of electric motors using pulse width modulated signal (PWM).
L293D division provides power for the chip and its controlled motors, allowing you to connect motors with high-voltage power supply than the chip. The separation of power circuits and electric motors may also be necessary to reduce interference caused by the Surge, work-related motors.
The principle of operation of each of the drivers included in the circuit is identical, so we consider the principle of one of them.
OUTPUT1 and OUTPUT2 connected to MOTOR1. The input ENABLE1, including the driver, will submit a signal (connected to the positive pole of power supply +5 V). If, in the inputs and INPUT1 INPUT2 does not beep, then the motor will not rotate. If the input INPUT1 connect the positive terminal of power supply and input INPUT2 – with the negative, the motor starts to rotate. Now let’s connect the input to the negative pole INPUT1 supply and input INPUT2 – positive. Motor starts to rotate in the opposite direction. Let us apply the same level of signals at once on both control inputs and INPUT1 INPUT2 (both inputs to connect the positive terminal of the power supply or a negative) – the motor will not rotate. If we remove the signal from the input ENABLE1, then for any variants having the input signals and INPUT1 INPUT2 motor will not rotate. Provide better principle of the driver motor can be, consider the following table:
Now consider the appointment of pins L293D.
- Inputs and ENABLE1 ENABLE2 responsible for the inclusion of each of the drivers that are part of the chip.
- Inputs and INPUT1 INPUT2 run the engine, connected to the outputs and OUTPUT1 OUTPUT2.
- Inputs and INPUT3 INPUT4 run the engine, connected to the outputs and OUTPUT3 OUTPUT4.
- Contact Vs is connected to the positive pole of a power supply of engines or just the positive terminal of power supply when the power supply circuit and a single engine. Simply put, this contact is responsible for the supply of electric motors.
- Contact Vss is connected to the positive pole of power supply. This pin provides power to the chip itself.
- Four pins GND is connected to “ground” (the common wire or the negative pole of power supply). In addition, through these contacts typically provide heat from the chip, so it is best to unsolder a sufficiently wide contact area.
Characteristics of IC L293D
- voltage motors (Vs) – 4,5 … 36V
- voltage integrated circuits (Vss) – 5V
- allowable load current – 600mA (per channel
- peak (maximum) output current – 1,2 A (per channel)
- logical “0” input voltage – up to 1,5 V
- logical “1” input voltage – 2,3 … 7V
- Switching speed of up to 5 kHz.
- Protection against overheating