Sensors

P.CHAITANYA 09131a1275 i.t

Shubham MundadaT.Y.B.TECH,ETC(A)ROLL NO:T3438 11/25/141SENSOR11/25/142

MOTION SENSOR211/25/20143OverviewWhat is a sensor?Motion sensorTypes of motion sensorsMotion DetectionTypes of Motion SensingDual sense technologyMotion Sensor in mobileMotion sensor in GamesConclusionReferences

11/25/20144SensorA sensor is a device which receives and responds to a signal.

A sensor (also called detector) is a converter that measures a physical quantity and converts it into a signal which can be read by an observer or by an (today mostly electronic) instrument.

11/25/20145Specifications of SensorAccuracy: error between the result of a measurement and the true value being measured.Resolution: the smallest increment of measure that a device can make.Sensitivity: the ratio between the change in the output signal to a small change in input physical signal. Repeatability/Precision: the ability of the sensor to output the same value for the same input over a number of trials.

11/25/20146Types of sensors There are many versions of each type which may use a different sensing principle or may be designed to operate within different ranges.

The sensors are used to measure and/or detect a huge variety of conditions including: temperature, pressure, level, humidity, speed, motion, distance, light or the presence/absence of an object and many other types.

11/25/20147Motion sensorsThe term Motion sensors can be used to refer to any kind of sensing system which is used to detect motion; motion of any object or motion of human beings.

Motion sensor is also called as motion detector.

Motion sensors are commonly used in security systems as triggers for automatic lights or remote alarms and similar applications.

11/25/20148 Types of Motion sensorsThe way in which a motion sensor works typically depends on the type of sensor being used, which often depends on the device that uses the sensor.

There are two basic types of motion sensors:

Active Sensors Passive Sensors

11/25/20149Active sensorsActive sensors emit a signal, typically an burst of (light, microwaves or sound) waves which is reflected by the surroundings.

The reflected signal is received by the sensor and takes necessary action.

When something moves within the area of an active motion sensor, the change in signal that is reflected to the sensor activates the system.

11/25/201410The active sensor is one of the most common and reliable sensors used in a security system.For example, when an automatic faucet senses hands underneath it, a device is signaled to run water in the sink.

Contd...11/25/201411Passive sensorPassive sensors are a type of motion sensor that do not emit a signal, but instead detect infrared radiation around the sensor.As this sensor detects temperature differences, it is well suited to detecting the motion of people by their body temperature.

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Use as a human detection sensor to automaticallyturn lights on when a person is present in a roomand to turn them off when nobody is there.When a person or animal moves through the area, heat from the movement is detected by the sensor, which then activates the system to which it is connectedContd...11/25/201413 Motion sensing is used in number of applications

Automated lighting system Security systems Smart Floodlights Burglar Alarm Radar Guns

TYPICAL APPLICATIONS11/25/201414Advantages of Motion sensorSaves time

Security

Easy to install

Saves energy

Powerful transmission

11/25/201415Motion detection Motion detection is the process of detecting a change in position of an object relative to its surroundings or the change in the surroundings relative to an object.

Motion can be detected by:Infrared (Passive and active sensors)Optics (video and camera systems)Radio Frequency Energy (radar, microwave motion detection)Sound (microphones and acoustic sensors)Vibration (seismic sensors)

11/25/201416TYPES OF MOTION SENSINGLocal Motion Sensing

Ultrasonic Motion Sensing

Microwave Motion Sensing11/25/201417Local motion sensingInfrared light is a spectrum of non-visible for humans at least light that is emitted by objects when they produce heat.

Infrared motion sensor systems are one of the cheapest and most reliable systems available.

An infrared motion detector uses infrared sensing to detect motion in a given area.

11/25/201418The use of infrared technology usually allows such a detector to only pick up on heat.

Infrared sensors are characterized by high sensitivity, low cost and are widely used.

An infrared motion detector can also be set to only pick up on certain levels of heat, making it possible to ignore small animals.

This type of detector is often used as part of a larger security system.

Contd...11/25/2014Ultrasonic motion sensingUltrasonic motion detectors use sound waves to detect motion. If movement is detected, the sound wave pattern is disrupted and alarm is signaled.

It senses motion by analyzing sound waves in its environment.

These frequencies are generally inaudible to humans and most animals and do not pass through most objects.

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11/25/201420Active motion sensors generate sound waves in the ultrasonic frequency range, typically around 30 to 50 kilohertz (kHz).

When no objects are moving in the area, the pattern of sound and the time it takes to bounce back remain the same. If something moves, the detector senses that the level or phase of the returning sound waves has shifted slightly. Contd...11/25/201421Microwave motion sensingMicrowave motion sensor systems send out microwaves that bounce off an object and back to the sensor.

The sensor then reads the frequency of the returning waves.

If an object is moving, the sensor receives different microwaves than the ones it sent out, signifying movement and setting off the alarm.

11/25/201422These types of motion sensor systems cover a larger area than infrared sensors, they are capable of penetrating walls.

They are more reliable over longer distances.

Their radiation is unhealthy for living organisms.

Despite this, they are the least popular motion sensor system on the market because of their their cost.Contd...11/25/201423Dual sense technologyDual technology systems use a combination of infrared and microwave motion sensor systems to provide the most complete coverage available.

Using both forms of technology allows dual motion sensor systems to reduce the occurrence of false alarms by combining the microwave technologys coverage range and the infrared technologys use of heat sensing.

The dual technology system is rapidly gaining popularity among homeowners and businesses alike.11/25/201424CELL PHONES WITH MOTION SENSORSThe motion sensor used in mobile phones is accelerometer which is a complex motion sensor.

It translates motion into action on the screen.

Accelerometers are used in tablet computers and digital cameras so that images on screens are always displayed upright.

11/25/201425Motion sensing in Games Motion sensing technology is an emerging technology in Gaming.

Our focus technology will be Microsofts Xbox360 Kinect peripheral, which is the first demonstrator of touch free motion sensing.

The primary innovation of Kinect (and the most secretive) is the device that enables advanced posture, gesture, facial, and voice recognition.

The Kinect is composed of three major hardware components: WebcamAn Infrared projector and sensorMicrophone

Kinect 11/25/20142611/25/201427Challenges facedLimited Camera And Sensor Capability

Better Audio Sensing Capability

Limited Body Recognition

11/25/201428Conclusion Motion sensing, though important in gaming, will ultimately make its biggest impact in non-gaming applications

POSITION SENSORS

Necessity of a sensor ? ? ?Acts as feedbackSensor Senses position of rotorIt converts the information of rotor position into a suitable electrical signal.This signal is used to switch ON and OFF of various semiconductor devices of electronic switching circuitry of BLPM motor

Rotor position can be determined by aHall Effectdevice (or devices), embedded in the stator, which provide an electrical signal representing the magnetic field strength. The amplitude of this signal changes as the magnetic rotor poles pass over the sensor. Other sensing methods areshaft encodersand also sensing the zero crossing points of currents generated in the unenergised phase windings. The latter method is known as "sensorless" position monitoring.TYPES OF ROTOR POSITION SENSORSOptical position sensor

Hall effect position sensor

Electronic position sensorsOPTICAL POSITION SENSORMainly used in Unipolar BLDC machinesRotor consists of optical sensors. The optical sensor consists ofA light sourcethree phototransistors P1, P2 and P3 mounted on the end plate of the motor, separated by 120o from each other A revolving shutter coupled to the shaft of the motor.

When the shutter revolves, the phototransistors get exposed to the light in the sequence of their numbers. In each revolution, the phototransistors generate the pulses PI1, PI1 and PI1which have duration and phase displacement of 120o.

Circuit Diagram

WORKINGWhen light falls on the phototransistors P1, it generates a pulse and transistor Q1 gets turned on. Current starts flowing through stator winding Ph1. This produces north pole at pole face of Ph1.South pole gets attracted towards it and reaches the axis of pole face of Ph1. Hence rotor revolves in anticlockwise direction. During the mean time, the light stops falling on P1 and starts falling on P2. Hence pulse PI1 is generated which turns on the transistors Q2.Current now starts flowing through the winding Ph2, producing a north pole. Hence rotor further rotates in anticlockwise direction so that rotor reaches the axis of the pole face of . In the meantime, starts falling on P3. This causes transistors Q3 to turn on which produces north pole at the pole face of Ph3. This rotates the rotor further in anticlockwise direction. Switching sequence repeats and continuous rotation of the rotor is obtained.HALL EFFECT SENSORSThe Hall Effect uses three hall sensors within the Brushless DC Motor to help detect the position of the rotor. The magnetic field changes in response to the transducer that varies its output voltage. Feedback is created by directly returning a voltage, because the sensor operates as an analogue transducer. The distance between the Hall plate and a known magnetic field can be determined with a group of sensors, and the relative position of the magnet can be deduced. Equivalent Circuit of a Hall element

Sectional View of BLDC with Hall sensor

Electronic SensorIn a brushless DC motor (BLDC), the rotor has permanent magnets and the stator has an electronically-controlled rotating field, using sensors (rotary encoders or back-EMF) to detect rotor position. As such they have no commutator, and tend to be more efficient and more powerful than commutated motors. They do require a more complicated motor controller.

Advantages of Electronic SensorHigh resolution sensing of absolute rotational position and speed without shaft encoders or Hall sensorsHigh reliability - eliminates mechanical and optical sensorsSensing circuits are integrated with motor drivers, automatically driving commutation and providing precise speed and position controlUses the magnetic characteristics of the motor to sense rotor position, eliminating the need for mechanical adjustments or alignmentsWorks at any speed, even while motor is stoppedEases packaging - no requirement to place components near motorNo injection of extraneous sense signals into motor windingsWorks with standard brushless motorsTouch Sensor

How Does a Touchscreen Work?

A basic touchscreen has three main components:1 Touch sensor;2Controller; 3 Software driver.The touchscreen is an input device, so it needs to be combined with a display and a PC or other device to make a complete touch input system.

Touch SensorA touch screen sensor is a clear glass panel with a touch responsive surface. The touch sensor/panel is placed over a display screen so that the responsive area of the panel covers the viewable area of the video screen. There are several different touch sensor technologies on the market today, each using a different method to detect touch input. The sensor generally has an electrical current or signal going through it and touching the screen can cause a voltage or signal change. This change is used to determine the location of the touch to the screen.

ControllerThe controller connects between the touch sensor and the PC. It takes information from the touch sensor and translates it into information that PC can understand. The controller determines what type of interface/connection you will need on the PC. Controllers are available that can connect to a Serial/COM port (PC) or to a USB port. Specialized controllers are also available that work with DVD players and other devices. Software DriverThe driver allows the touchscreen and computer to work together. It tells the computer's operating system how to interpret the touch event information that is sent from the controller. Most touch screen drivers today are a mouse-emulation type driver. This makes touching the screen as same as clicking your mouse at the same location on the screen. This allows the touchscreen to work with existing software and allows new applications to be developed without the need for touchscreen specific programming. Touchscreen Technology Resistive touchscreenCapacitive touchscreenInfrared touchscreenSurface acoustic wave (SAW) touchscreenStrain gauge touchscreenOptical imaging touchscreenDispersive signal technology touchscreenResistive touchscreenStructureResistive touch screens consist of a glass or acrylic panel that is coated with electrically conductive and resistive layers made with indium tin oxide (ITO) .The thin layers are separated by invisible spacers.

4-wire resistive touchscreen

5-wire resistive touchscreenThe construction of the panels are similar with 4-wire technology, but for a 5-wire touch screen all four bus bars are connected to the lower, non-flexible layer of the screen. The flexible layer is always used as a sense layer to read the voltage connection point to the bottom layer.

8-wire resistive touchscreenResistive touchscreenCharacters:Cost effective solutions Activated by a stylus, a finger or gloved hand Not affected by dirt, dust, water, or light 75%~85% clarifyresistive layers can be damaged by a very sharp objectProjected-capacitive touchscreenStructureProjected capacitive touchscreens have front and back protective glassproviding optical and strength enhancement options.Its middle layer consists of a laminated sensor grid of micro-fine wires, andoptical enhancement options.

Projected-capacitive touchscreenDuring a touch, capacitance forms between the finger and the sensor grid.The embedded serial controller in the touchscreen calculates touch location coordinates and transmits them to the computer for processing.

Surface-capacitive touchscreenStructureSurface capacitive technology consists of a uniform conductive coating on a glass panel. Electrodes around the panels edge evenly distribute a low voltage across the conductive layer, creating a uniform electric field.

Surface-capacitive touchscreenWorking principleA human body is an electric conductor, so when you touch the screen with a finger, a slight amount of current is drawn, creating a voltage drop. The current respectively drifts to the electrodes on the four corners. Theoretically, the amount of current that drifts through the four electrodes should be proportional to the distance from the touch point to the four corners. The controller precisely calculates the proportion of the current passed through the four electrodes and figures out the X/Y coordinate of a touch point.

Capacitive touchscreenCharacters:Durable and resistant to scratches for demanding applications Faster and more responsive Immune to surface contaminants Superior optical clarity, brighter display and less surface reflection Must be touched by finger, will not work with any non-conductive input Infrared touchscreenInfrared (IR) technology relies on the interruption of an IR light grid in front of the display screen. The touch frame contains a row of IR-light emitting diode (LEDs) and photo transistors, each mounted on two opposite sides to create a grid of invisible infrared light. The IR controller sequentially pulses the LEDs to create a grid of IR light beams. When a stylus, such as a finger, enters the grid, it obstructs the beams. One or more photo transistors from each axis detect the absence of light and transmit signals that identifies the x and y coordinates. Infrared touchscreen

Infrared touchscreenCharacters:Clear as glass, improves reading abilityMost durable surface

SAW touchscreenSurface waves are readily absorbed when a soft object such as a fingertip touches the substrate.SAW Touch Screen use pure glass with transmitting and receiving piezoelectric transducers for both the X and Y axes. The touch screen controller sends an electrical signal to the transmitting transducer, which converts the signal into ultrasonic waves within the glass.When you touch the screen, you absorb a portion of the wave traveling across it. The received signal is then compared to the stored digital map, the change recognized, and a coordinate calculate.

SAW touchscreen

SAW touchscreenCharacters:Durable glass construction High optical clarity Activated by a finger, gloved hand or soft tip Not completely sealable, can be affected by large amounts of dirt, dust, and / or water in the environmentTechnologyCapacitiveSAWInfraredResistiveTransparenceVery good >92%Very good >92%Very good >92%75%~85%ResolutionGoodGoodLimited due tospacing of IRsensorsgoodSurfaceContaminants/durabilityResistant tomoisture andother surfacecontaminantsAdversely affected bymoisture orSurfacecontaminantsPotential forFalse activationor dead zonesFrom SurfaceContaminantsUnaffected by Surfacecontaminants.Polyester topsheet is easilyscratchedSensor substrateGlass with ITO coatingGlass with ITO coatingAny substratePolyester top sheet, glasssubstrate withITO coatingDisplay size8.4"-21"10.4"-30"10.4"-60"up to 19"Touch methodHuman touchfinger, glovedhand or soft tip Can use any pointing deviceCan use any pointing deviceMulti-touch technologyMulti-touch denotes a set of interaction techniques which allow computer users to control graphical applications with several fingers. Products:Apple iPhone, iPod touch, MacBook Air, and MacBook Pro Microsoft Surface 11/25/201471Environment Sensors

The Android platform provides four sensors that let you monitor various environmental properties. You can use these sensors to monitor relative ambient humidity, illuminance, ambient pressure, and ambient temperature near an Android-powered device. All four environment sensors are hardware-based and are available only if a device manufacturer has built them into a device. With the exception of the light sensor, which most device manufacturers use to control screen brightness, environment sensors are not always available on devices. Because of this, it's particularly important that you verify at runtime whether an environment sensor exists before you attempt to acquire data from it.

11/25/201472The rapid development and miniaturization of technologies used in digital cameras, cell phones, and wireless computers are allowing scientists to develop networks of small sensors that will lead to a new era of monitoring the health and stability of our environment. Wireless devices half the size of a cell phone now exist with sensors to measure light, wind speed, rainfall, temperature, humidity, and barometric pressure. Moreover, these devices store collected data, process desired data averages or transformations, and then transmit requested data by radio frequency along a series of wireless hops to an Internet node.

11/25/201473Deploying arrays of hundreds of these sensor devices will allow us to fill a gap between local-scale ecological observations and environmental data from scattered regional weather stations.

Such micrometeorological measurements at fine spatial and temporal scales will help scientists understand the relationship of broad-scale changes in global climate and local microclimate that control many ecosystem and physiological processes.11/25/201474

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