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Вы можете ознакомиться и скачать презентацию на тему Visual Output. Доклад-сообщение содержит 25 слайдов. Презентации для любого класса можно скачать бесплатно. Если материал и наш сайт презентаций Mypresentation Вам понравились – поделитесь им с друзьями с помощью социальных кнопок и добавьте в закладки в своем браузере.

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IMPLEMENTING IOE Assist. Prof. Rassim Suliyev - SDU 2017

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Visual Output Lets the Arduino show off Arduino supports a broad range of LED devices Use digital and analog outputs for visualization Digital output All pins that used for digital input can be used as output as well Digital output causes the voltage on a pin to be either high (5 volts) or low (0 volts) digitalWrite(outputPin, value) pinMode(outputPin, OUTPUT)

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Analog Output Refers to levels that can be gradually varied up to their maximum level analogWrite(pin, val) Used to control such things as the intensity of an LED Is not truly analog, but behave like analog Uses a technique called Pulse Width Modulation (PWM) Emulates an analog signal using digital pulses Works by varying the proportion of the pulses’ on time to off time

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Pulse Width Modulation More commonly called “PWM” Computers can’t output analog voltages Only digital voltages (0 volts or 5 volts) But you can fake it if you average a digital signal flipping between two voltages For example...

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PWM Output voltage is averaged from on vs. off time output_voltage = (on_time / off_time) * max_voltage

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PWM Used everywhere Lamp dimmers Motor speed control Power supplies Noise making Three characteristics of PWM signals Pulse width range (min/max) Pulse period (= 1/pulses per second) Voltage levels (0-5V, for instance)

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Arduino PWM Arduino has built-in PWM On UNO they are pins 3, 5, 6, 9, 10, 11 Use analogWrite(pin,value) pin: the pin to write to. value: the duty cycle: between 0 (always off) and 255 (always on). It operates at a high, fixed frequency 490HZ for most pins (except pins 5 and 6 which run at 980HZ) Great for LEDs and motors Uses built-in PWM circuits of the ATmega8 chip No software needed

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Arduino PWM Higher level output is emulated with pulses that are on more than they are off Pulses are repeated quickly enough almost 500 times per second on Arduino pulsing cannot be detected by human senses

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LED specifications LED is a semiconductor device (diode) Two leads, an anode and a cathode The device emits light (photons) when Vanode > Vcathode + forward voltage Anode is usually the longer lead and flat spot on the housing indicates the cathode LED color and forward voltage depend on the construction of the diode Typical red LED has a forward voltage of around 1.8 volts Limit the current with a resistor, or the LED will burn out

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Consult an LED data sheet Arduino pins can supply up to 40 mA of current This is plenty for a typical medium intensity LED, but not enough to drive the higher brightness LEDs or multiple LEDs connected to a single pin

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Adjusting the Brightness of an LED Connect each LED to an analog (PWM) output

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Driving High-Power LEDs Arduino can handle current up to 40 mA per pin Use a transistor to switch on and off the current Arrow indicates a +V power source +5V power pin can supply up to 400 mA or so If an external power supply is used, remember to connect the ground of the external supply to the Arduino ground

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How to Exceed 40 mA per Pin Connect multiple pins in parallel to increase current beyond the 40 mA Don’t try to use a single resistor to connect the two pins This technique can also be used to source current It does not work with analogWrite

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Adjusting the Color of an LED RGB LEDs have red, green, and blue elements in a single package common anode or common cathode

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Adjusting the Color of an LED

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Driving a 7-Segment LED Display Contains 8 LEDs (including Decimal Point indicator) Common Anode & Common Cathode

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Driving a 7-Segment LED Display

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Multidigit, 7-Segment: Multiplexing Corresponding segments from each digit are connected together

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Multidigit, 7-Segment: Multiplexing

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Multiplexing To control many LEDs use a technique called multiplexing Multiplexing is switching groups of LEDs in sequence Usually arranged in rows or columns Scanning through the LEDs quickly enough Creates the impression that the lights remain on Through the phenomenon of persistence of vision Charlieplexing uses multiplexing along with the fact that LEDs have polarity They only illuminate when the anode is more positive than the cathode Switch between two LEDs by reversing the polarity

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Controlling an LED Matrix 8X8 LED matrix contains 64 LEDs Anodes connected in rows and cathodes in columns

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Lighting Each Pixel of LED Matrix

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Displaying Images on an LED Matrix

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Controlling LEDs: Charlieplexing Charlieplexing - increases the number of LEDs that can be driven by a group of pins Based on the fact that LEDs only turn on when anode more positive than the cathode