1. Rebecca Bruce and Susan Reiser, May 2015 Analog Input and Output

2. Rebecca Bruce and Susan Reiser, May 2015 330 Ohm resistor Demo 1: Digital Output on a Breadboard Connect the blue wire to pin 13 Run File > Examples > Basic> Blink

3. Rebecca Bruce and Susan Reiser, May 2015 Digital Input/Output Digital IO is binary valued—it’s either on or off, 1 or 0 Internally, all microprocessors are digital, why? 1 0

4. Rebecca Bruce and Susan Reiser, May 2015 IO Pins Image from Theory and Practice of Tangible User Interfaces at UC Berkley

5. Rebecca Bruce and Susan Reiser, May 2015 Demo 2: Digital Input Add a push-button switch to the breadboard - Connect the green wire to pin 2 Run File > Examples > Digital > Button 330 Ohm resistor

6. Rebecca Bruce and Susan Reiser, May 2015 Digital? Analog? 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

7. Rebecca Bruce and Susan Reiser, May 2015 Variable Resistance: Potentiometers It is a variable resistor

8. Rebecca Bruce and Susan Reiser, May 2015 Analog Input Connect to analog pin A0 Run File > Examples > Basic> ReadAnalogVoltage Open the serial port monitor to see the output

9. Rebecca Bruce and Susan Reiser, May 2015 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 Analog to Digital Image credit: Eoin Brazil

10. Rebecca Bruce and Susan Reiser, May 2015 Analog Output Computers can’t output analog voltages –Only digital voltages (0 volts or 5 volts) Simulating an analog signal with Pulse Width Modulation (PWM) –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.

11. 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

12. Rebecca Bruce and Susan Reiser, May 2015 PWM is Everywhere Lamp dimmers, motor, speed control, power supplies, noise making, etc.