Download Analog Input and Output

Analog Input and Output
Rebecca Bruce and Susan Reiser, May 2015
Demo 1: Digital Output on a Breadboard
330 Ohm
resistor
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Connect the blue wire to pin
13
Run File > Examples >
Basic> Blink
Rebecca Bruce and Susan Reiser, May 2015
Digital Input/Output
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Digital IO is binary
valued—it’s either on or
off, 1 or 0
Internally, all
microprocessors are
digital, why?
1
0
Rebecca Bruce and Susan Reiser, May 2015
IO Pins
Image from Theory and Practice of Tangible User Interfaces at UC Berkley
Rebecca Bruce and Susan Reiser, May 2015
Demo 2: Digital Input
330 Ohm
resistor
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Add a push-button switch to
the breadboard
- Connect the green wire
to pin 2
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Run File > Examples >
Digital > Button
Rebecca Bruce and Susan Reiser, May 2015
Digital? Analog?
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Digital has two values: on and off
Analog has many (infinite) values
Computers don’t really do analog input, they
quantize
Remember the 6 analog input pins---here’s
how they work
Image credit: Tod Kurt
Rebecca Bruce and Susan Reiser, May 2015
Variable Resistance: Potentiometers
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It is a variable resistor
Rebecca Bruce and Susan Reiser, May 2015
Analog Input
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Connect to analog pin A0
Run File > Examples >
Basic>
ReadAnalogVoltage
Open the serial port
monitor to see the output
Rebecca Bruce and Susan Reiser, May 2015
Analog to Digital
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Number of states
or “bins” is the
resolution
Arduino resolution
is 10-bits (1024
values, including 0)
5/1023 = 4.9 mV
smallest voltage
change you can
measure
Image credit: Eoin Brazil
Rebecca Bruce and Susan Reiser, May 2015
Analog Output
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Computers can’t output analog voltages
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Only digital voltages (0 volts or 5 volts)
Simulating an analog signal with Pulse
Width Modulation (PWM)
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Can’t directly supply 2.5V, but can pulse the
output on and off really fast to produce the
same effect---the same effective voltage.
Rebecca Bruce and Susan Reiser, May 2015
Analog Output
Vary the
effective voltage
by modulating
the width of
the high pulse
Image credit: Tod Kurt
Rebecca Bruce and Susan Reiser, May 2015
PWM is Everywhere
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Lamp dimmers, motor, speed control,
power supplies, noise making, etc.
Rebecca Bruce and Susan Reiser, May 2015