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Embedded systems and sensors
Lennart
Herlaar
Part 2
Interaction
technology
1
Contents
• Sensors and actuators
• Coding and sketches
• Circuits
• Pull-up resistors
• Voltage dividers
Sensors and actuators
Sensors and actuators
• Sensors sense the world around us
• From a physical property to a digital value
• Actuators manipulate the world around us
• From a digital value to a physical property
• Type of physical property may vary
• Level of complexity may vary
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Basic binary sensors, basic analog sensors
Complex analog sensors, complex digital sensors
Integrated modules
Bimetal, thermistor, TMP036, DS18B20, fire alarm
Sensors
Actuators
And then some…
Coding and sketches
My First Circuit
• Controlling a LED
9
Declaration of variables
Initialization (only once)
Hello World! (Blink)
Main loop (ad infinitum)
Arduino programming language
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C (or C++) variant
"Sketches" instead of programs
"Small" language
Complex features are hidden from view
• But are available if needed
• Usual control structures
• if, if-else, for, while, do-while, switch
• Usual functions
• Parameterization
• return
Arduino programming language
• Usual operators
• ==, !=, <, =<, &&, ||, !, ++, +=, *=, <<, etc.
• Usual datatypes
• boolean, char, byte, (unsigned) int, long, float,
double, string, array, String (object)
• Usual standard functions
• min(), abs(), sqrt(), cos(), tan(), random(), etc.
• Boring language... !? Simple... !?
• Lots of syntactic sugar
Arduino programming language
• Digital I/O
• pinMode(pin, INPUT/OUTPUT/INPUT_PULLUP)
• digitalWrite(pin, HIGH/LOW)
• digitalRead(pin)
• LOW < 1.5 Volt, HIGH > 3 Volt
• Analog I/O
• analogRead(pin)
• 0 .. 5 Volt, ranging 0 .. 1023 (10 bit resolution A/D
converter)
• analogWrite(pin, 0 .. 255)
• Pulse Width Modulation (PWM), 500 Hz
PWM
Arduino programming language
• Time
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millis()
micros()
delay()
delayMicroseconds()
• Structure
• setup()
• loop()
• Our Hello World application has a problem!
• More on that later…
Circuits
Connecting an RGB led
• Three leds in one package…
• …sharing a common lead
• Common anode versus
common cathode
Connecting a button
• Unconnected input pins
are floating
• A pull-down or pull-up
resistor is needed
• Pull-up resistors are
generally preferred
Connecting a light sensor
• Light Dependent Resistor (LDR)
• A microcontroller can't sense resistance directly
• …but can sense voltage levels
• Convert resistance to voltage
• …using a voltage divider
Motion and distance sensors
• Connecting these is pretty
straightforward
• You may need to solder on
some wires and configure
Connecting a temperature sensor
• Your temperature sensor is quite advanced
• DS18B20 compatible one-wire device
• One-wire protocol
• Actually a communication bus
• Needs a pull-up
Connecting an LCD
• Lots of wires!
• Backlight with series
resistor
• Voltage divider for
contrast
• Easy coding!
• Library