The Dewi Sant Greenhouse
Control Project Lesson 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 2
The Greenhouse Project
Slide 3
Conditions in the greenhouse
1 What do plants need to make them grow?
2 What conditions may change in a
greenhouse?
Slide 4
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 5
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 6
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 7
What might this be?
Start
Yes
Is Val 1 > 30?
Turn Output 5 on
No
Turn Output 5 off
Val 1 is a temperature sensor
Val 1 is a temperature sensor
Slide 8
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 9
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 10
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 11
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).
Slide 12