Fundamentals of Mixed Signals and Sensors

Fundamentals of Mixed Signals and Sensors Page 1 of 7 Introduction to Mixed Signal and Sensors I. INTRODUCTION: Sensor design in embedded systems has traditionally required analog experts to interface with the sensors...

Fundamentals of Mixed Signals and Sensors Page 1 of 7 Introduction to Mixed Signal and Sensors I. INTRODUCTION: Sensor design in embedded systems has traditionally required analog experts to interface with the sensors, but the use of mixed signal products relegates embedded sensor design to a typical EE. Previously, interfacing with an analog sensor required the use of external amplifiers and filters to conditional the signal properly before digitizing the signal in a microcontroller’s ADC. By utilizing a mixed signal controller, the amplifiers and filters are integrated, allowing the designer to program each component in the signal path. This integration simplifies the design and reduces the time and complexity of the system. This module provides an introduction to Introduction to Mixed Signal and Sensors IV. LESSON PROPER ORIGINS OF REAL-WORLD SIGNALS AND THEIR UNITS OF MEASUREMENT. Webster's New Collegiate Dictionary defines a signal as "A detectable (or measurable) physical quantity or impulse (as voltage, current, or magnetic field strength) by which messages or information can be transmitted." Key to this definition are the words: detectable, physical quantity, and information. A signal is an electrical or electromagnetic current that is used for carrying data from one device or network to another. It is the key component behind virtually all: In signal processing, a signal is a function that conveys information about a phenomenon. In electronics and telecommunications, it refers  Fundamentals of Mixed Signals and Sensors Page 2 of 7 Introduction to Mixed Signal and Sensors to any time varying voltage, current or electromagnetic wave that carries information. A signal may also be defined as an observable change in a quality such as quantity. Signal Characteristics  Signals are Physical Quantities  Signals are Measurable  Signals Contain Information  All Signals are Analog Units of Measurement  Temperature: °C  Pressure: Newtons/m2  Mass: kg  Voltage: Volts  Current: Amps  Power: Watts Signals Classification Signals are classified into the following categories:  Continuous Time and Discrete Time Signals  Deterministic and Non-deterministic Signals  Even and Odd Signals  Periodic and Aperiodic Signals  Energy and Power Signals  Real and Imaginary Signals 1. Continuous Time and Discrete Time Signals A signal is said to be continuous when it is defined for all instants of time. A signal is said to be discrete when it is defined at only discrete instants of time  Fundamentals of Mixed Signals and Sensors Page 3 of 7 Introduction to Mixed Signal and Sensors 2. Deterministic and Non-deterministic Signals A signal is said to be deterministic if there is no uncertainty with respect to its value at any instant of time. Or, signals which can be defined exactly by a mathematical formula are known as deterministic signals. A signal is said to be non-deterministic if there is uncertainty with respect to its value at some instant of time. Non- deterministic signals are random in nature hence they are called random signals. Random signals cannot be described by a mathematical equation. They are modelled in probabilistic terms. 3. Even and Odd Signals A signal is said to be even when it satisfies the condition x(t) = x(-t) Example 1: t2, t4… cost etc. Let x(t) = t2 x(-t) = (-t)2 = t2 = x(t) ∴, t2 is even function Example 2: As shown in the following diagram, rectangle function x(t) = x(-t) so it is also even function.  Fundamentals of Mixed Signals and Sensors Page 4 of 7 Introduction to Mixed Signal and Sensors A signal is said to be odd when it satisfies the condition x(t) = -x(-t) Example: t, t3... And sin t Let x(t) = sin t x(-t) = sin(-t) = -sin t = -x(t) ∴, sin t is odd function. Any function ƒ(t) can be expressed as the sum of its even function ƒe(t) and odd function ƒo(t). ƒ(t ) = ƒe(t ) + ƒ0(t ) where ƒe(t ) = ½[ƒ(t ) +ƒ(-t )] 4. Periodic and Aperiodic Signals A signal is said to be periodic if it satisfies the condition x(t) = x(t + T) or x(n) = x(n + N). Where T = fundamental time period, 1/T = f = fundamental frequency. The above signal will repeat for every time interval T0 hence it is periodic with period T0. 5. Energy and Power Signals A signal is said to be energy signal when it has finite energy. A signal is said to be power signal when it has finite power. Note: A signal cannot be both, energy and power simultaneously. Also, a signal may be neither energy nor power signal.  Fundamentals of Mixed Signals and Sensors Page 5 of 7 Introduction to Mixed Signal and Sensors Power of energy signal = 0 Energy of power signal = ∞ 6. Real and Imaginary Signals A signal is said to be real when it satisfies the condition x(t) = x*(t) A signal is said to be odd when it satisfies the condition x(t) = -x*(t) Example: If x(t)= 3 then x*(t)=3*=3 here x(t) is a real signal. If x(t)= 3j then x*(t)=3j* = -3j = -x(t) hence x(t) is a odd signal. Note: For a real signal, imaginary part should be zero. Similarly for an imaginary signal, real part should be zero. Mixed-Signal Circuit, are also called hybrid circuits, contain elements and properties of both Analog Circuit and Digital Circuit. Examples: Comparators, Timers, PLLs, ADCs (Analog-to-Digital Converters), and DACs (Digital-to-Analog Converters). SENSORS Sensors are sophisticated devices that are frequently used to detect and respond to electrical or optical signals. A Sensor converts the physical parameter (for example: temperature, blood pressure, humidity, speed, etc.) into a signal which can be measured electrically. In the broadest definition, a sensor is a device, module or subsystem whose purpose is to detect events or changes in its environment and send the information to other electronics, frequently a computer processor. A sensor is always used with other electronics. Different Types of Sensors The following is a list of different types of sensors that are commonly used in various applications. All these sensors are used for measuring one of the physical properties like Temperature, Resistance, Capacitance, Conduction, Heat Transfer etc Temperature Sensor, Proximity Sensor, Accelerometer, IR Sensor (Infrared Sensor), Pressure Sensor, Light Sensor, Ultrasonic Sensor, Smoke, Gas and Alcohol Sensor, Touch Sensor, Color Sensor, Humidity Sensor, Tilt Sensor, Flow and Level Sensor  Fundamentals of Mixed Signals and Sensors Page 6 of 7 Introduction to Mixed Signal and Sensors Temperature Sensor One of the most common and most popular sensor is the Temperature Sensor. A Temperature Sensor, as the name suggests, senses the temperature i.e. it measures the changes in the temperature. In a Temperature Sensor, the changes in the Temperature correspond to change in its physical property like resistance or voltage. Proximity Sensors A Proximity Sensor is a non-contact type sensor that detects the presence of an object. Proximity Sensors can be implemented using different techniques like Optical (like Infrared or Laser), Ultrasonic, Hall Effect, Capacitive, etc. Infrared Sensor (IR Sensor) IR Sensors or Infrared Sensor are light based sensor that are used in various applications like Proximity and Object Detection. IR Sensors are used as proximity sensors in almost all mobile phones. Ultrasonic Sensor An Ultrasonic Sensor is a non-contact type device that can be used to measure distance as well as velocity of an object. An Ultrasonic Sensor works based on the properties of the sound waves with frequency greater than that of the human audible range.  Fundamentals of Mixed Signals and Sensors Page 7 of 7 Introduction to Mixed Signal and Sensors The following is a small list of projects based on few of the above mentioned Sensors. Light Sensor – Light Detector Using Ldr , Smoke Sensor – Smoke Detector Alarm Circuit, Alcohol Sensor – How To Make Alcohol Breathalyzer Circuit? , Touch Sensor – Touch Dimmer Switch Circuit Using Arduino, Color Sensor – Arduino Based Color Detector, Humidity Sensor – Dht11 Humidity Sensor On Arduino, Tilt Sensor – How To Make A Tilt Sensor With Arduino?