Remote controlled DC Drive Circuit

First let us start with system block diagram

System Block-Diagram: -

As shown in above figure major components are St3049, micro controller 89C51 and dual H-Bridge driver L293D. Let us see function of each one by one

IR sensor: - demodulates 38KHz wave and gives RC5 code to ST3049

ST3049: - decodes RC5 code and gives 6 bit data to 89C51

89C51: - this is the heart of entire system. It performs following tasks.

• Starts or stops DC motor
• Changes its directions also varies its speed
• Indicates speed increase / decrease on bar graph
• Indicates start / stop and CW / CCW direction of motor on indicators

L293D: - it provides sufficient current (up to 1A) to drive DC motor

Circuit diagram: -

Connection: - as shown in figure P1 is connected with data outputs of St3049. 8-LED bar graph is connected with P2. Four LEDs are connected with P3.0, P3.1, P3.4 and P3.5. Pins P3.6 and P3.7 drives DC motor through L293D chip. Pin P3.2 is connected with CA pin of ST3049. 12 MHz crystal along with 2 33pf capacitor provides basic clock signal. C3, D5 and R1 forms power on reset circuit. One push button is given to reset micro controller.

Operation: -

• As ST3049 receives valid RC5 code it will generate external interrupt for micro controller
• As external interrupt arrives micro controller will get 6 bit code form P1
• It will compare the code with the code that are already stored in memory. Here I have selected four codes as given in below table

• Key on remote	6 bit code	Function
  stand by (on/off)	12	to start or stop motor
  mute	13	to change direction
  volume up	16	increase speed
  volume down	17	decrease speed

• When a match found controller will perform that particular task. Like starting motor, changing direction, increase / decrease speed etc.
• Al song with that it will also give indication on LEDs

• Green LED	Motor running
  Red LED	Motor stop
  Yellow LED	CW direction
  Orange LED	CCW direction

• 8 LED bar graph shows increase or decrease in speed in 8 steps

This entire operation depends upon the program embedded in micro controller. So now let us understand software program

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