bionic_arduino_class4.pdf

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Bionic Arduino
Introduction to Microcontrollers with Arduino
Class 4
20 Nov 2007 - machineproject - Tod E. Kurt
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What’s for Today
• Controlling Servos
• About the I2C bus
• Using I2C on Arduino
• About Accelerometers
• Nintendo Wii Nunchuck as Input Device
• About PWM
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Recap: Blinky LED
Make sure things still work
compile
upload
Load “File/Sketchbook/Examples/Digital/Blink”
TX/RX flash
b l i n k b l i n k
Change the “delay()” values to change blink rate
sketch runs
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Pulse Width Modulation
• 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...
• More commonly called “PWM”
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Output voltage is averaged from on vs. off time
PWM
output_voltage = (on_time / off_time) * max_voltage
5 volts
3.75 Volts
0 volts
75% 25%
75% 25% 75% 25%
5 volts
2.5 Volts
0 volts
50% 50% 50% 50% 50%
50%
5 volts
0 volts
1.0 Volts
20% 80%
20% 80% 20% 80%
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