The Dewi Sant Greenhouse Control Project Lesson 2

Slide 2

We are learning today:

Discuss the uses of control in everyday life

Understand how a greenhouse can be controlled and monitored, using a computer

Know how to create flowcharts to show the operation elements in a greenhouse

Slide 3

The Greenhouse Project

Slide 4

Conditions in the greenhouse

1 What do plants need to make them grow?

2 What conditions may change in a greenhouse?

Slide 5

How do greenhouses work?

To get the best plant growing conditions temperature and humidity (moisture in the air) have to be controlled.

The greenhouse has temperature and humidity sensors linked to a computer, and the computer has a program storing details of the correct temperature and humidity settings.

The greenhouse is fitted with a heater, sprinkler and window motor, also linked to the computer.

If the humidity falls below the values stored in the program, the computer activates the sprinklers and close the windows.

If the temperature falls outside the values stored in the program, the heater is activated by the computer.

The system monitors the conditions night and day with immediate response to any changes. To alter the growing conditions the values in the computer program can of course be changed.

Slide 6

Annotate our greenhouse mimic

val 1 = analogue heat sensor

val 2 = analogue light sensor

input 1 = digital moisture sensor

output 5 = heater

output 6 = light

mot a = open / close window

mot b = sprinkler

Slide 7

Comparing values in a feedback loop

Sometimes, an input value is not as simple as being on or off

Values can be within a range

We need to be able to get the computer to test that a value falls within a range of values and respond appropriately

Slide 8

Start

Is Val 1 > 30?Yes

No

Turn Output 5 off Val 1 is a temperature sensor

What might this be?

Turn Output 5 on

Val 1 is a temperature sensor

Slide 9

Lesson tasks

1. Use moisture sensor to turn on the sprinkler

2. Use heat sensor to turn on the heater

3. Use light sensor to turn on the light

4. Use moisture sensor to close the window and turn on the sprinklers for 10 seconds

Remember to print out each flowchart, stick in your book and annotate to explain what is happening in each step

Slide 10

Evidence: One to two A4 pages

Name

Title: “Greenhouse Assessment”

Date

A clear print screen of your greenhouse control system, showing the mimic

An explanation of your system, talking through every part of your system to show how it works

Slide 11

We are learning today:

To build a control system that operates all of the parts of the greenhouse system in an efficient way

– Level 4: A mostly working system that controls most parts of the greenhouse

– Level 5: A fully working system that controls most of the parts of the greenhouse in one big flowchart

– Level 6: A fully working system that controls all of the parts of the greenhouse and uses as least one subroutine

– Level 7: A fully working system that controls all of the parts of the greenhouse and uses several effective subroutines

Slide 12

Task Two

Write an article for the school magazine about the greenhouse project. Find a suitable photo to illustrate the article.

You might include information on:

– the benefits of using the computer to control the greenhouse;

– how you can monitor and control the temperature, light and heat;

– how practical the project is (whether it is feasible).