Subsystem: P3

Task Title:
Timer / Delay
Resistor / Capacitor
Timer

 

Introduction and Aims

To make a timer circuit that will delay the sounding of a buzzer. It is operated by the press of a switch. The delay time is adjustable from 0 to 45 seconds using capacitors. (Before you start, you will need to quickly research module P6 in the subsystems info link top right).

Subsystem Circuit and Block Diagram

IP2
(+)
Switch Trigger
P3
RC Delay
P6
Op Amp
Comparator
OP1
Sourced
Buzzer
 


Investigating the System

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

1, The component with a C next to it is known as a . (see P3 Resistor / Capacitor Timer)

2, When the push switch across the capacitor is pressed, the capacitor is .

3, As the capacitor charges up, the across it gets greater.

4, The switch connected to the resistor allows to build up on the capacitor.

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 P3 project guide.