Subsystem: P7

Task Title:
Variable Tone Generator
555 Timer
Astable/Clock

 

Introduction and Aims

Using a 555 Timer I.C., connected as an Astable (P7), we will create a variety of output sounding tones. We will vary the pitch by adjusting either the variable resistor (Rb) or the capacitor (C). The tones are produced because the 555 integrated circuit can produce an output square wave by repeatedly switching its output signal on and off very quickly.

Subsystem Circuit and Block Diagram

 

IP2
+ going
Switch
Input
P7
555 Timer
Astable
OP1
Sourced
L.E.D. & Piezo Sounder
   


Investigating the System

Using the "Library of Subsystems" here and the circuit and block diagrams above, complete the following:

1, The square box labelled 555 Timer is an .

2, The 555 Timer chip is made up of components. (See P7 Astable Clock).

3, The term Astable means the output of the 555 device will .

4, The timing of the 555 circuit is controlled by 3 components. These are , and (See P7 Astable Clock).

Modelling the System/Circuit

There are different ways to model and test circuits before components are soldered to a P.C.B.. Modelling is an important stage as it helps you spot any problems and make modifications more easily.

Method 1: Breadboard

Using this method, components are pushed into the interconnected holes as shown in the diagram below. The lines shown, indicate which holes are internally connected.

Print this page and by using the circuit diagram above, design the breadboard layout for this system.

Method 2: Computer Simulation

To begin, ask your supervisor if circuit simulation software is available on your PC. This method allows you to build up your circuits quickly and cheaply in a virtual environment but will not give you hands-on experience of the components you will be using when finally soldering your P.C.B..

Method 3: Using OnTrack modelling hardware

See P7 project guide.