Subsystem: P5

Task Title:
Keep Cool Fan
Transistor Driver
(Output Buffer)

Introduction and Aims

Example System: This is a design and make project called "Keeping it Cool".

Design Brief: Produce a system that automatically keeps electronic equipment at a safe working temperature.

Specification: When the temperature reaches a critical point, operate a cooling fan which will remain switched on until the temperature reduces to the required level.

Solution: This automatic cooling fan system will detect a rise in temperature and use P5, an output buffer, to provide us with enough power to run a motor/ fan and sound an alarm. The Input sensor will detect the temperature and control the output/motor via the transistor driver.


Subsystem Circuit and Block Diagram

IP1
Heat Sensor
P6
OpAmp
Comparator
P5
Output
Buffer
OP2
Motor
Driver
OP1
Buzzer
Output


Investigating the System

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

1, Find the value of VR1 - ohms (see IP1)
2, Find the name of Tr1 - (see P5)
3, Find the value of R1 - (see OP2 Inductive outputs).

4, The output stage (motor driver) is connected to the "c" of the transistor. "c" stands for .

5, The voltage required on the base (b) to turn the transistor on is approximately volts.

 

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 P5 project guide.