SE-3910Real-time Systems

• Week 2, Class 2– Return stuff, New HW Assignment!– Quiz! (Possibly with review)

• Ohm’s Law• Kirkhoff’s Current Law• Switches• Using/reading an oscilloscope• Frequency / Period

– Signals• Square, Sine, Saw-tooth, Random• Pulse Width Modulation (PWM) SE-3910 - Dr. Josiah Yoder

Slide style: Dr. HornickMuch Material: Dr. Schilling, Some from Dr. Hornick, etc.

1

Waveform Terminology

• Amplitude• Peak-to-peak voltage• Peak voltage (alternative defs)

• Period• Frequency (review)

SE-3910 - Dr. Josiah YoderSlide style: Dr. Hornick

Much Material: Dr. Schilling2

Sketching & Listening to Waveforms

• Sine wave

• Square wave

• Sawtooth wave(s)

• Random wave

• Efffect of changing– Amplitude– Frequency– Phase (time shift)

On sound!

SE-3910 - Dr. Josiah YoderSlide style: Dr. Hornick

Much Material: Dr. Schilling3

Technical Goals

• How does one control the speed of a motor?

• How does one change the brightness of a light-bulb?

SE-3910 - Dr. Josiah YoderSlide style: Dr. Hornick

Much Material: Dr. Schilling4

Pulse-Width-Modulation… in traffic

SE-3910 - Dr. Josiah YoderSlide style: Dr. Hornick

Much Material: Dr. Schilling5

Pulse-width modulation terminology

SE-3910 - Dr. Josiah YoderSlide style: Dr. Hornick

Much Material: Dr. Schilling 6

• Determine the duty cycle (D)

• Multiply the duty cycle by the peak voltage (Vp)

eff P p

DT

V D V VT

In-class exercise

• How can you control the brightness of an LED, using tools we have discussed so far?

• How would you accomplish this if you went into lab right now?

SE-3910 - Dr. Josiah YoderSlide style: Dr. Hornick

Much Material: Dr. Schilling7

Advantages of Pulse-Width Modulation

• Click to add text

SE-3910 - Dr. Josiah YoderSlide style: Dr. Hornick

Much Material: Dr. Schilling8

Power of a signal (If time)

• P = IV• I = V/R• P = …• Let R = 1 (Ohm)• What is the instantaneous power of a

sinusoid?• What is the average power of a sinusoid?• What is the average power of a PWM signal?

SE-3910 - Dr. Josiah YoderSlide style: Dr. Hornick

Much Material: Dr. Schilling9