EXPERIMENT : Programing a microcontroller ... · •Arduino directly can provide only 40mA of current within an max of 5V output which is insufficient to rotate the motor. So we need

Parikshit Saha IIT Kanpur

EXPERIMENT : Programing a microcontroller

- Microcontroller : basic programing

- Sensor interfacing

- Motor control : DC Motor, DC servo, etc.

- Encoder interfacing


What is Arduino ? • Arduino is an open-source hardware which consists of ATMEL

microcontroller (ATmega 16/32) based programmable circuit board

and a easy to use Software IDE (Integrated Development

Environment) that runs on a computer.


Arduino Pin Diagram


Programing details: Port Pin Data Directionality

• Input

• When you want to take information from the external world (sensors) into the MCU

• Output

• When you want to change the state of something outside the MCU (turn a motor on or off, etc.)

• Pins default to input direction on power-up or reset

• Your program can set or change the directionality of a pin at any time


Pin Voltages

• Microcontrollers are fundamentally digital devices

• Information is ‘coded’ in two discrete states:

• HIGH or LOW (logic: 1 or 0)

• Voltages

• TTL • 5 V (for HIGH)

• 0 V (for LOW)

• 3.3 V CMOS

• 3.3 V (for HIGH)

• 0 V (for LOW)


Digital I/0 Syntax pinMode(pin, mode)

Sets pin to either INPUT or OUTPUT

digitalRead(pin) Reads HIGH or LOW from a pin

digitalWrite(pin, value) Writes HIGH or LOW to a pin (1 or 0)

analogRead(Pin)

analogWrite(Pin, Value), Value is between 0 to 255


Arduino Basic Coding Structure

<define global variables and include header files here> void setup() {

< executed only once>

< define input/output mode for digital pins > } void loop() {

<infinite loop>

<things like input from sensors, sending output etc. > }


LED blink Arduino Demo


Two colour LED glow – Arduino Demo


Hall Sensor Interfacing


Motor Interfacing with Arduino

By Parikshit Saha


Analog Out (PWM) Concept

• No facility exists on most microcontrollers to directly output an analog voltage (i.e., a voltage that varies continuously over the range of 0 to 5V) • Use Pulse Width Modulation (PWM) to approximate

• Digital outputs are capable of 0V or 5V

• Over a fraction (ton) of a time period tcycle, keep pin at 5V, the rest of the time, at 0V

• Average voltage is proportional to ton/tcycle, called the ‘Duty Cycle’


Output voltage is averaged from on vs. off time


PWM – Pulsewidth Modulation

• Square wave with fixed (high) frequency, but variable ON time..

• Fraction of time period signal is high varies between 0 and 1. Expressed in percentage, called duty cycle.

• Dedicated PWM pins on Arduino boards. Voltage obtained on PWM pin is duty cycle/100 * 5 V, when analog signal sent to the pin is duty cycle/100 * 255.


DC Motor Interfacing

• Dc Motor have two terminals vcc & gnd

• Arduino directly can provide only 40mA of current within an max of 5V output which is insufficient to rotate the motor. So we need a specific type of circuit known as Motor Driver to drive the motor.

• Some Dc Motor also has a higher V-I requirement based on torque of operation. (600mA, 4.5V to 36V)

• H-bridge circuit is used.

• Different types of H-bridge circuits are L293, L293D, L298

• Some Advanced level H-bridge circuits are VNH2SP30, VNH5019 have the higher voltage- current motor driving capabilities.


DC Motor Interfacing (contd.)

• fhgfation


Encoder ON-OFF Demo

• fhgfation


Encoder Counter Demo

• fhgfation


What is Servo Motor?

• 3 Wire terminals vcc, gnd & signal

• In signal terminal we feed angle of rotation in degree while using directly ‘servo.h’ Arduino library

• Internally Dc Motor + Potentiometer


Servo Motor Interfacing (from library function)


Servo Motor Interfacing (building from scratch)


DC Motor with Encoder


Encoder ON-OFF Demo

• fhgfation


Encoder Counter Demo

• fhgfation

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EXPERIMENT : Programing a microcontroller ... · •Arduino directly can provide only 40mA of current within an max of 5V output which is insufficient to rotate the motor. So we need