Subsystem: OP2

Task Title:
Interactive Display
Inductive Outputs

Introduction and Aims

To produce a system that could be used to control an interactive display at a museum or exhibition.
By using a Darlington Pair Amplifier, we will be modelling a touch switch similar to the type shown in P1. The output power of this amplifier is sufficient to drive the low torque motor which is connected in series with a 33 ohm resistor (Note - the resistor drops the voltage to the motor by forming a potential divider).The diode on module OP2 prevents the voltage generated by the coil in the motor (back e.m.f.) returning to the transistors and damaging them. Please note all outputs containing coils are Inductive and can produce this harmful back e.m.f.

Subsystem Circuit and Block Diagram

 

IP1
Touch
Sensor
P2
Darlington
Pair
OP2
Sourced
Motor
   


Investigating the System

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

1, The component D1 is a . It is used to stop dangerous back e.m.f. produced by the from getting back to the transistors. (see above description)

2, An output device such as a solenoid, that is made by turning wire round and round into a coil, is known as an device.

3, The capacitor in parallel with the diode is used to (see OP2 Inductive outputs).

4, Resistor R1 is used to . (see OP2)

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 OP2 project guide.