INTERFACING HARDWARE WITH MICROCONTROLLER GUIDED BY: Prof. ASIF SIR 1. AKSHAY KIRAN 2. DEEP PARIKH 3. JIGAR PATEL 4. TILAK PATEL ,05,D2D06,09 EC 3 rd YEAR

. What is a Microcontroller ? A microcontroller (or MCU) is a computer-on-a-chip. It is a type of microprocessor emphasizing self- sufficiency and cost-effectiveness, in contrast to a general-purpose microprocessor (the kind used in a PC). The only difference between a microcontroller and a microprocessor is that a microprocessor has three parts - ALU, Control Unit and registers (like memory), while the microcontroller has additional elements like ROM, RAM etc.

. ATMEGA32/ATMEGA32L  High-performance, Low-power AVR 8-bit Microcontroller  Up to 16 MIPS Throughput at 16 MHz  32K Bytes of In-System Self-Programmable Flash  1024 Bytes EEPROM  2K Byte Internal SRAM  Two 8-bit Timer/Counters, One 16-bit Timer/Counter  In-System Programming by On-chip Boot Program  Four PWM Channels  8-channel, 10-bit ADC  Programmable Serial USART  Internal Calibrated RC Oscillator  External and Internal Interrupt Sources  Power-on Reset  32 Programmable I/O Lines

. ATMEGA32 Operating Voltage V Speed Grades 0 – 16 MHz

. Pin Diagram

c. C - CODECOMPILERHEX - CODE COMPUTER MICRO CONTROLLER

. Configuring PORT PINS Each PORT consists of three registers  DDRX (Data Direction Register)  PORTX  PINX Where X = A, B, C, D

. DDRX  The DDXn bit in the DDRx Register selects the direction of pin n.  If DDXn is written logic one, PXn is configured as an output pin.  If DDXn is written logic zero, PXn is configured as an input pin. Where n = 0,1, ,7 For Example If DDRA = 0x0F ( )  The Lower bytes of PORTA are configured as output pins  The Higher bytes of PORTA are configured as input pins

. PORTX When PORTXn is configured as Input Pin  Writing logic ONE to this pin, activates pull-up resistor.  Writing logic ZERO to this pin, deactivates pull-up resistor When PORTXn is configured as Output Pin  Writing logic ONE to this pin, drives the port pin HIGH  Writing logic ZERO to this pin, drives the port pin LOW

. PINX  PINXn is used to read the value of particular port pin  Independent of the setting of Data Direction bit DDRXn, the port pin can be read through the PINXn Register bit

. Interfacing with Microcontroller  LED  Switches  DC Motor  Sensors  Stepper Motor

INTERFACING LED.

. LED – Light Emitting Diode  Maximum potential drop across LED will be approximately 2V.  Maximum current tat can be allowed through am LED is approximately 30ma.  Resistor should be added in series with LED to limit the current through it.

. Calculating LED resistor value R = (Vs – V L )/I Vs = supply voltage V L = Voltage drop across LED ( around 2V) I = 15 to 30 ma

LED’s connected to 1. PORTA0 2.PORTB0

LED BLINK PROGRAM.

#ifndef F_CPU #define F_CPU UL // 16 MHz clock speed #endif #include #include int main(void) { DDRC = 0xFF; //Makes PORTC as Output while(1) //infinite loop { PORTC = 0xFF; //Turns ON All LEDs _delay_ms(1000); //1 second delay PORTC= 0x00; //Turns OFF All LEDs _delay_ms(1000); //1 second delay } }

INTERFACING DC MOTOR.

. DC Motor  DC Motors are small, inexpensive and powerful motors used widely.  These are widely used in robotics for their small size and high energy out.  A typical DC motor operates at speeds that are far too high speed to be useful, and torque that are far too low.  Gear reduction is the standard method by which a motor is made useful.  Gear’s reduce the speed of motor and increases the torque

. Choosing a DC Motor  DC Motor with Gear head  Operating voltage 12V  Speed Depends on our application Some available speeds in market  30 RPM  60 RPM  100 RPM  150 RPM  350 RPM  1000 RPM

. Drive basics of DC Motor Red wireBlack wireDirection of rotation Positive Negative Clock wise Negative PositiveAnti clock wise Logic Direction 1 0Clock 0 1Anti clock

. Direction Pulse to Clock wise A and C Anti Clock wise B and D Bi-Direction control of DC Motor H-Bridge Ckt using transistors for bidirectional driving of DC motor

. H-Bridges in IC’s to reduce the drive circuit complexity  The most commonly used H-Bridges are L293D and L298  L293D has maximum current rating of 600ma  L298 has maximum current rating of 2A  Both has 2 H-Bridges in them  These are designed to drive inductive loads such as relays, solenoids  Can be used to drive 2 DC motors or 1 stepper motor

DC MOTOR CODE. #ifndef F_CPU #define F_CPU UL // 16MHz clock speed #endif #include int main(void) { DDRC = 0xFF; //PORTB as Output while(1) { //Rotates Motor in Anticlockwise PORTC = 0x01; // _delay_ms(4000); //Stops Motor PORTC = 0x00; // _delay_ms(4000); //Rotates Motor in Clockwise PORTC = 0x02; // _delay_ms(4000); //Stops Motor PORTC = 0x03; // _delay_ms(4000); }

INTERFACING SWITCHES.

. Switches Active Low  When pressed shorts the corresponding pin to ground Active high  When pressed shorts the corresponding pin to Vcc

Active low Active high

. Sensors Commonly used sensors in the field of robotics are  IR Digital sensors  IR analog sensors

. IR Digital sensors Transmitter  IR led connected to 38KHz oscillator Receiver  TSOP1738 IR Analog sensors Transmitter  IR LED Receiver  IR Photodiode

. IR Analog sensor

. STEPPER MOTOR  STEPPER MOTOR is a brushless DC motor whose rotor rotates in discrete angular increments when its stator windings are energized in a programmed manner.  Rotation occurs because of magnetic interaction between rotor poles and poles of sequentially energized stator windings.  The rotor has no electrical windings, but has salient and/or magnetized poles.

. 4 – Lead stepper 5 – Lead stepper 6 – Lead stepper8 – Lead stepper

Full Step driving of Stepper Motor Full step wave drive

Full Step driving of Stepper Motor Full step 2 phases active

. Half Step driving of stepper motor

. Choosing a Stepper motor  12 V operating voltage  1.8 degree step  6 Lead  250 t0 500 ma of current or Coil resistance of 20 ohms to 40 ohms  Size and shape depends on application  In most of the robotics cube shaped motors are preferred with frame size of 3.9 to 4 cm

. Commonly used IC’s for driving Stepper motor  ULN2803 It has 8 channels It channel has maximum current rating of 500ma can be used to drive 2 unipolar stepper motors  L293d  L297 & L298

. ULN2803

. A B C D Bi – Polar driving of Stepper Motor