bionic_arduino_class4.pdf

Bionic Arduino

Introduction to Microcontrollers with Arduino

Class 4

20 Nov 2007 - machineproject - Tod E. Kurt

What’s for Today

• Controlling Servos

• About the I2C bus

• Using I2C on Arduino

• About Accelerometers

• Nintendo Wii Nunchuck as Input Device

• About PWM

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

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”

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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