LEGO® WeDo (V) - Programming in Scratch

LEGO® WeDo (V)

Programming in Scratch*

By Edwar Romero

Cover image by Osvaldo Romero

We continue here with our plan to dominate the world! One

LEGO® brick at a time. The best part is that we can start

doing it with programmable WeDo™ bricks the best we can.

We continue here our programming quest in Scratch as the

software for our battles. In previous issues of this magazine,

we have covered the WeDo software basics and the equivalent

commands used in the open platform Scratch.

We have talked before about how to program a few basic

things, like the fundamentals for the motor and the different

alternatives to turn it on and off. Last time we started talking

about different options for programming the Amazing

Mechanisms included with the WeDo software: Dancing Birds,

the Smart Spinner and the Drumming Monkey, and how to do

it using Scratch. This time we continue with the next set of 3

mechanisms: the Hungry Alligator, the Roaring Lion and the

Flapping Bird (designs 4, 5 and 6 from the gure below).

Let’s start with the Hungry Alligator. The WeDo software

program begins when hitting the letter “A” on the keyboard

to turn the motor one way to open the powerful jaws of

this alligator. After that, it will make a scary bite sound and

immediately turn the motor the other way to close the jaws

and bite everything that gets close enough. It will chomp for a

few seconds before the next bite. The next image shows this

sequence programmed in WeDo.

You can program it in Scratch in a similar fashion. You need to

look for the Control tab to nd the “when __ key pressed” and

selected a letter on the drop down menu. The letter “a” was

selected for this example.

You can select the space bar since you don’t have to look at

the keyboard constantly to nd it. You need to use the “motor

direction” to open the alligator jaws, after that the option “motor

on for” 1 second under the Motion menu. Next, you need to

select the option “play sound”. By default the meow sound

appears, you may want to change it since it doesn’t sound

ferocious enough for a hungry alligator. So, you need to import

a new sound for this task. You need to go to the zone where

you are programming, look for the Sounds tab, hit the Import

button, and look around for a suitable sound. I used the one

called Slurp in the Human folder. You may choose a different

one, download it from the Internet or even record your own

version. Don’t forget to choose the sound from the drop down

menu, otherwise your alligator will sound like a kitten. Once

done, you need to select the motor direction in the opposite

way to see the jaws closing for chomping down whatever the

fangs caught.

We can start thinking about having our own robotic security

system using LEGO® bricks. What if you have a wolf or huge

bear as a guardian for your home, built completely with LEGO

and programmed to behave as you like? It seems like world

domination is one step closer!

Next is the Roaring Lion design. The programming in WeDo is

as shown below. One key is used to get it up and roaring and

another to send it to sleep. When the big cat is up and roaring

like a erce beast, you need to congure the power level of the

motor and check the motor is turning the right way. Don’t forget

to add a ferocious sound for this feline.

When our big cat is tired of roaring, it needs to go for a good

night’s sleep. For that, you need to program the motor power

and check if the motor is turning in the right direction for the

lion to go to rest. You also need to nd a sleepy sound to show

this cat is quite friendly when it is tired, so we can get close

without getting into trouble.

Performing the programming in Scratch shouldn’t be difcult

for this task after all we have learned with the previous design.

You need to verify and test several motor power levels for the

lion to behave like the king of the jungle it is. We don’t want

our robotic friend to fall apart while performing, do we? The

most difcult part for the Roaring Lion programming is nding

a hungry lion sound. You can try your best impersonation to

record this sound. You can be the voice of your own creation!

You can also resort to a sound le of your liking from the

Internet if the ones in Scratch are not erce enough.

For going to sleep, our feline friend can be programmed in

Scratch as shown below. You need to be really creative when

choosing a sleeping sound. You can try between the ones

available in the Scratch folder to see if there is something you

like or you can try to record the best impersonation you can for

this sleepy cat.

In order to complete the three designs from the Wild Animals

set, we still need to work with the Flapping Bird. The Flapping

Bird is a lot less complicated than previous designs. It only

uses the tilt sensor to activate the wing apping sound.

The basic WeDo program should look like the image below.

We have a loop that allows the cycle to repeat as many times

as needed. There is also the wait command connected with

the tilt sensor. The tilt sensor is on the horizontal position (no

tilt), so when is moved to another position it will activate the

wind apping sound for this huge bird. You can imagine this

bird moving its powerful wings through the air. Is quite terroric,

isn’t it?

Working in Scratch, the program should look similar to the

one found below. The “forever if” loop can be found under the

Control menu. If you look under the Operators menu, you’ll nd

the equal to block “_=_”. You can play with the value to nd

other interesting congurations. Going through the Sensing

menu, close to the end you’ll nd the “sensor value” block. On

that drop down menu, you will discover the tilt sensor like the

one on the image.

Finding the right sound for the apping of the wings for our big

bird is a complete challenge for this creation too. You can try

and record the sound effects for this design as well. You can

also search on the Internet for the sound of your preference.

That’s all for now folks, stay tuned for the advanced

programming of these creations in the next issues of

HispaBrick Magazine®.

You can nd more information, and building and programming

instructions for the designs presented here and many more at:

www.wedobots.com

www.facebook.com/wedorobots

* This tutorial uses Scratch version 1.4 - The use of LEGO®

WeDo in Scratch 2.0 is still experimental.