Презентация Getting Input from Sensors онлайн

Содержание слайда: IMPLEMENTING IOE Assist. Prof. Rassim Suliyev - SDU 2017

Содержание слайда: Getting Input from Sensors Sensors give report on the world around it Sensors convert physical input to an electrical signal The electrical signal depends on the kind of sensor and how much information it needs to transmit Some use substance that alters their electrical properties in response to physical change Others are sophisticated electronic modules that use their own microcontroller to process information

Содержание слайда: Methods to provide information Digital on/off - switch a voltage on and off Tilt sensor Motion sensor Analog - provide an analog signal (voltage) Temperature sensor Light intensity sensor Pulse width - measure the duration of a pulse Distance sensors

Содержание слайда: Methods to provide information Serial - provide values using a serial protocol RFID reader GPS module Synchronous protocols: I2C and SPI The I2C and SPI digital standards were created for microcontrollers to talk to external sensors and modules These protocols are used extensively for sensors, actuators, and peripherals E.g: compass module, LCD display

Содержание слайда: Consumer devices Contain sensors but are sold as devices in their own right Provide sensors already incorporated into robust and ergonomic devices They are also inexpensive as they are mass-produced PS2 mouse PlayStation game controller

Содержание слайда: Data sheets Contains information about a sensor’s output signal Available from the company from which you bought the device Google search of the device part number or description Are aimed at engineers designing products to be manufactured Usually provide more detail than you need Information on output signal will usually be in a section: Data format, interface, output signal, or something similar Check the maximum voltage!!!

Содержание слайда: Noises Reading sensors from the messy analog world is a mixture of science, art, and perseverance Use trial and error method to get a successful result Common problem: Sensor just tells you a physical condition has occurred But not what caused it Skills to acquire with experience: Putting the sensor in the right context Location, range, orientation Limiting its exposure to things that you don’t want to activate it Separating the desired signal from background noise Use a threshold to detect when a signal is above a certain level Take the average of a number of readings to smooth out noise spikes

Содержание слайда: Detecting Movement Detect when something is moved, tilted, or shaken Tilt sensor - switch that closes a circuit when tilted Ball bearing in a box with contacts at one end Sensitive to small movements of around 5 to 10 degrees

Содержание слайда: Detecting Movement

Содержание слайда: Shake detection

Содержание слайда: millis() function Returns long type value - number of milliseconds since the current sketch started running Will overflow (go back to zero) in approximately 50 days Determine the duration of the event by subtracting the pre-stored start time from the current time long startTime = millis(); …do something… long duration = millis() - startTime;

Содержание слайда: Similar digital output sensors Mechanical switch sensors can be used in similar ways Float switch can turn on when the water level in a container rises to a certain level The way a ball cock works in a toilet cistern A pressure pad can be used to detect when someone stands on it

Содержание слайда: Detecting Light Detect changes in light levels Something passes in front of a light detector Detecting when a room is getting too dark Use a light dependent resistor (LDR) Changes resistance with changing light levels Produces a change in voltage

Содержание слайда: Detecting Light Not full range of possible values (0-1023) Since voltage will not be swinging between 0-5 V LDR - simple kind of sensor called a resistive sensor Range of resistive sensors respond to changes in different physical characteristics

Содержание слайда: When a room is getting dark

Содержание слайда: Detecting motion

Содержание слайда: PIR motion detection PIR - passive infrared sensor measures infrared light radiating from objects Made from pyroelectric materials which generate energy when exposed to heat

Содержание слайда: Measuring Distance Ultrasonic distance sensor Measure the distance of an object (2 cm - 3 m) Modules includes ultrasonic transmitters, receiver and control circuit Basic principle of work: Trigger trig pin for at least 10us with a high level signal The module automatically sends eight 40 kHz and detect whether there is a pulse signal back Time of high output duration at echo pin is the time from sending ultrasonic to returning.

Содержание слайда: How it works Ultrasonic sensors provide a measurement of the time it takes for sound to bounce off an object and return to the sensor Pulse width is proportional to the distance the sound traveled The speed of sound is 340 meters per second - 29 microseconds per centimeter Roundtrip = microseconds / 29 Distance in centimeters is: microseconds / 29 / 2

Содержание слайда: Measuring Distance

Содержание слайда: pulseIn() and delayMicroseconds() pulseIn(pin, value[, timeout]) Reads a pulse (either HIGH or LOW) on a pin pin: the number of the pin on which to read the pulse value: type of pulse to read: either HIGH or LOW timeout (optional): the number of microseconds to wait for the pulse to be completed. Default is one second Returns the length of the pulse in microseconds or 0 if no complete pulse was received within the timeout delayMicroseconds(us) Pauses the program for the us amount of time (in microseconds) specified as parameter

Содержание слайда: IR distance rangers Generally provide an analog output Have greater accuracy than ultrasonic sensors Range of 10 cm to 1 m or 2 m Output from the IR sensor is not linear (not proportional to distance) Distance values can be found by trial and error

Содержание слайда: Measuring Temperature LM35 heat detection sensor Produces an analog voltage directly proportional to temperature 1 millivolt per 0.1°C (10mV per degree) The sensor accuracy is around 0.5°C, Functional range: from -40°C to 150°C

Содержание слайда: Measuring Temperature

Содержание слайда: Detecting Vibration Piezo sensor responds to vibration Produces a voltage in response to physical stress The more it is stressed, the higher the voltage Piezo is polarized (has + and -) A high-value resistor (1 megohm) is connected across the sensor

Содержание слайда: Detecting Vibration