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Interactive Arts & Tech
IAT 267
Helmine Serban

Producing Motion Two basic types of motion Linear motion Rotary motion-involves motors Converting Rotary Motion into a Liner Motion Use basic mechanics and simple machines -lever -pulley -gear -cam -ratchets -linkages Characteristics of Motors Rated Voltage Current -stall current -running current Motor speed Position resolution (for servo and stepper motors) Torque Servomotors -can be positioned from 0-180 degrees usually -easy three-wire PWN, 5V interface Use of Servomotors Many objects that you want to turn or rotate can be manipulated with a servo -cameras -mirrors -directed lighting, etc. An easy correlation between a potentiometer and a servo can be established: turn the potentiometer and the servo turns Servo Control Servo connection to Arduino Need to provide the servomotor with power from the 5V Arduino board Ground connection to the GND on the Arduino board/breadboard Code Controlling a servo is just a matter of determining how long in microseconds you need to send each command to the servo -writing a pulse to the motor that is the desired length E.g. A value between 0 and 180 degrees (followed by a non-digit character) is sent using the serial connection to a computer to the servo Arduino Servo Library The library is included with the Arduino IDE -it lets Arduino control one or more servomotors Three methods: -attach() -wire() -read() attach() method Starts reading the Servo instance on the pin passed into the method servo.attach(pin); servo.attach(pin, min, max); // optionally set the min and max pulse widths read() method Reads the current angle of the servo (the value passed to the last call to write()) Using multiple servos Servos draw considerable power, so if you need more than one or two, you will need to power them up from a separate supply -connect the grounds of the Arduino and external power supply together If you need more servos than Arduino can handle (more than 12), you can used a dedicated servo controller device Advantages of Using Servomotors Easy to control and precision A servo read the amount of voltage passed in to determine how far to rotate within a limited range -the most common range for a servo is 180 degrees -the servo can move from any point in that range to any other point clock/counter clockwise Powerful tools for controlling anything that needs a controllable, repeatable movement There are many to choose from -different sizes and performance The signals used to control servos are almost always the same Identification Physical Identity Presence -is it near me? Address -where is it? Human senses: how objects are recognized -look, feel, pick up, shake, listen to, smell, taste How Computers Identify Objects Use information from sensors Optical Recognition Can take many forms -video color tracking -shape recognition -barcode Identifiers -colors -shapes -barcodes (can be fluid/mean different things depending on context) Shape and Pattern Recognition Recognizing a color: simple computationally Recognizing a physical object: more challenging 2D geometry has to be known -from every angle -able to compare any view we get from the object -computer compares patterns therefore, it does not understand the object as a discrete entity Solution: simplify the object to 2D barcode Barcode Recognition Pattern of dark and light lines or cells used to encode an alphanumeric string Computer reads the barcode by scanning the image and interpreting the light and dark bands as 0 or 1 Scanning is done by camera or photodiode 1D barcode-ISBN of a book -scanner or camera needs to read the image only along one axis 2D barcode (Quick Response Code) -2D matrix-more information density 2D Barcode Recognition Using a Webcam Generate QR codes using an online QR code generator Decode tags using a camera and a Process
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