Lesson 4 Variables

Lesson Objectives To understand what variables are To understand how they can be used in control technology

Variables In which other subjects have you used variables? What do we use them for?

Variables A variable assigns any value to a letter. Like in algebra a2xb2=c2 , a b and c are all equal to numbers.

Task 1: Open Flowol and open the Big Wheel mimic. This mimic has 4 inputs and 4 outputs You can control 3 lights and 1 motor

How does it work? How does a Big Wheel actually work? They move around but stop each time to let people on and off.

Click the big wheel Notice how every time the big wheel goes around, the light on the steps lights up How could we use this to make the wheel stop each time to let people on?

With a variable! We need to create a variable. We will call it x. Each time the light on the steps lights up it stop the wheel and add 1 to x. When x equals a certain number (when all the people are on) we can make it rotate normally.

Create a new variable At the top right, click the XY symbol. This will automatically create 2 variables called X and Y that you can see here.

X=0 Before we start we need to make sure that x=0. Create this flow chart

Create a flow diagram which does the following Turn wheel forward Is the light on the steps on? If yes, turn wheel off. If no, loop to turning wheel forward Delay Let A=A+1 Is A = to 24? If it is all the people are on and the wheel can keep going. If not, loop back to turn wheel forward Delay as long as the ride is Turn wheel off.