Subsystem: P8

Task Title:
Movement Limiter

555 Timer
Monostable

 

Introduction and Aims

We will be modelling a simple Closed Loop Control System to electrically open a door. It is similar to the type of circuit used on trains and buses.
After a button has been pressed to request the opening of a door, a motor will start to move the door. A 555 Monostable will have been turned on and will be controlling the motor. When the door reaches its fully open position a limit switch will be pressed and will feedback information to reset the 555 Monostable and consequently turn the motor off.

Subsystem Circuit and Block Diagram

IP3
- going
Switch Trigger
P8
555 Timer
Monostable
P5
Output
Buffer
OP2
Motor
Driver
OP1
Sinked
LED
Output


Investigating the System

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

 

1, The term monostable means stable in state.

2, R and C are important components because they control the of the monostable.

3, P5 the Output Buffer is used to .

4, If the reset button is pressed ie taken to zero volts,whilst the monostable is switched on, then the output voltage will go to volts.

5, R1 is in series with the motor which tells us that the voltage across the motor is the power supply voltage.

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 P8 project guide.