Subsystem: OP1

Task Title:
Dual Alert Warning
Sourcing and Sinking
Outputs

Introduction and Aims

To produce an alerting system that uses light as well as sound to draw your attention.
The system is driven by a 555 Astable I.C. which produces an output signal slowly changing between 0 volts and + volts. The outputs are connected so that the L.E.D. works when it is sinked (555 Astable output = 0 volts) and the buzzer works when it is sourced (555 Astable output = + volts)
.

Subsystem Circuit and Block Diagram

 

IP2
+ going
Switch
Input
P7
555 Timer
Astable
OP1
Sourced
L.E.D. Sinked
Buzzer
   


Investigating the System

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

1, The buzzer, LED and Resistor are connected in .

2,When the voltage output of the 555 I.C. is 0 volts on pin 3, the voltage across the buzzer is volts.

3, When the voltage output of the 555 I.C. is 9 volts on pin 3, the voltage across the buzzer is volts and the voltage across the LED and resistor is volts.

4, The LED and buzzer work at different times because they are either being or .

 

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 OP1 project guide.