Chapter 3:Signals and Systems¶

Introduction¶

Signals, including audio (speech, acoustics, music), image (video, multimedia, medical scans) and remote sensing data, are phenomena that vary with time, space, or other parameters. Systems can be regarded as devices that manipulate signals. The disciplines of signal and image processing are concerned with the analysis and synthesis of signals and their interaction with systems. In communications, the objective is to transfer information (signals) from one or many sources to one or many destinations, which requires the design of transmission schemes (e.g., modulation and coding), receivers, and filters.

The Systems, Signals, and Communications area of interest covers the fundamentals of analog and digital signals and systems, the mathematical tools for the analysis of determinate and random signals, and applications to digital signal processing, digital image processing, and digital/analog communications.

Section Overview¶

This lab uses the KL-46 z in a simple circuit that acts like a piano(or a simple music instrument ). Using a variable resistor as input, an attached speaker will produce at least an octave of distinct musical notes. Later in the lab.

Objectives¶

• Learn to use a schematic to correctly build a circuit.
• Download the ECE111 code.
• Program the Mbed KL-46z.

Materials¶

• KL-46z.
• USB to Mini USB Cable.
• ECE111 Kit.
  • 0.1uF Capacitor.
  • Speaker.
  • Prototyping Wires.

Building the Circuit¶

In the previous lab, a potentiometer was created out of conductive paper. In this lab, another potentiometer will be made out of conductive paper, but this time attached to a Popsicle stick so that it will be more robust. This potentiometer will be used as a voltage divider to send an analog voltage to the Mbed. The Mbed will then interpret the analog voltage as a specific pitch and play the pitch using a small speaker as shown in Figure.

The Figure is a schematic for the piano circuit that is being built. A schematic is a diagram which shows every component and connection in a circuit. The schematic in Figure shows how to correctly connect the potentiometer, speaker, capacitor, and Mbed.

Finish building the circuit according to the schematic. In the end, you will have built a miniature piano!

Solder Wires to Paperclips¶

Paperclips will be used to create the electrical connection between the wires and the conductive paper. To solder wires to the paperclips, follow these instructions and refer to Figure .

• Remove the plastic cover from the end of a female to female breadboard wire, exposing the conductive metal as in Figure.
• Insert a paperclip into the metal end
• Solder the paperclip to the wire to ensure a good electrical connection.

Download the Source Code¶

The code for each lab for ECE 111 is located on the Mbed page for the class. Follow these instructions to download the code.

• Navigate to the ECE 111 page on the Mbed website.
• item Download .
• Save the .zip file in the desired location.

Program the Mbed¶

Study Questions¶

• What are some of the applications of signals and systems in everyday life? (Think of anything that has a transmitter and receiver.) Name at least two.}
• Name two potential uses for a Python GUI application in other classes.
• How does the capacitor affect the sound generated from the piano? Why does it do this?}

Challenge¶