Motors and Ports

Try It — Which Way Does It Go?

Think about walking across the room. Your brain does not send one signal to “your body.” It sends a signal to your left leg and a separate signal to your right leg.

The brick works the same way. Two motors, two wheels, two separate commands.

Find the ports

Look at the brick. Across the top edge are four ports with letters — A, B, C, D — for motors. Across the bottom edge are four more with numbers — 1, 2, 3, 4 — for sensors. Letters up top, numbers down below.

• I found all eight ports and can point to motor ports A–D on top and sensor ports 1–4 on the bottom
• The left wheel motor is in port B and the right wheel motor is in port C
• My robot is on a block with the wheels in the air

The robot is a mirror of itself

Here is something strange, and it matters for everything you do later. The two wheel motors are identical — but they are mounted facing opposite directions, one on each side of the robot.

So “clockwise” does not mean the same thing to both wheels. Spin both motors clockwise and one wheel rolls the robot forward while the other rolls it backward.

The wheel-spin trick

You do not need a program to see this. Connect the app to your brick and open the view that shows the connected devices — you will see a live number for each motor.

On the brick, use the arrow buttons to reach the Brick Apps tab and open Port View. It shows a live number for every port. Arrow over to a wheel motor’s port. Then turn that wheel with your hand, in the direction that would drive the robot forward, and watch its number change on the screen.

Both wheels moved the robot’s-forward direction under your hand — but the two numbers changed in opposite ways. What does that tell you about the two motors?

Learn It — The Motor Blocks

The pink Motors category runs one motor at a time. Its main block needs three pieces of information: which motor, which way, and how much.

• The first dropdown is the port — which motor.
• The arrow is the direction: ↻ clockwise or ↺ counterclockwise — from the motor’s point of view, not the robot’s. That distinction is the whole mirror lesson from a minute ago.
• The number and unit say how much: rotations, degrees, or seconds.

Speed is a separate block, and it is a percentage — set it once and every motor block after it uses it:

Two kinds of motor block

Look closely at the shelf and you will find two different ways to run a motor — and the difference between them is the most important idea in this project.

Why you always need the wait

Here is the thing that surprises everyone. Look at this program:

The wheels will not move. Not even a twitch.

The brick switches both motors on, and then — faster than you can blink — reads the next blocks and switches them off again. Remember from Project 2: it moves through blocks far quicker than your eye can follow.

In your own words: what is the wait block actually doing while the motors run?

A stop is not instant

Stop motor switches the power off — but a spinning wheel does not freeze mid-turn. On the ground, the robot coasts a little further before it truly stops. Keep that in the back of your mind: it is why, in the next project, a stop always gets a moment to settle before anything else happens.

Which end is the front?

Your driving base has two driven wheels and one small free-rolling ball — a caster — that just holds the robot up. The driven wheels are the front; the caster trails along behind.

Do It — Make It Turn

Robot on the block. Wheels in the air. Every time.

Step 1 — Write your first motor program

Make a new project called Motors — names in the project name, that is your attribution. Build the start-wait-stop program from Learn It: left wheel counterclockwise, right wheel clockwise, wait 2 seconds, both stops. Run it. Watch the wheels.

• Both wheels spun the robot’s-forward direction for about 2 seconds

Did both wheels spin the robot forward? If one went backward, which part of which block do you need to change?

Step 2 — Prove the wait matters

Delete the wait block. Run.

Now put it back.

• The wait is back and the program works again

Step 3 — Prove the stops matter

Now delete both stop motor blocks instead. Run. Watch carefully — including what happens after the program looks finished.

Put them back. Getting into the habit now matters: a robot on a real field with nothing telling its motors to stop is a robot leaving the table.

• The stops are back

Step 4 — Explore speed

Add set speed blocks for both motors at the top of the stack. Change the percentage, run, and record what you notice. Keep the wait at 2 seconds every time so it is a fair test.

Is speed 100 exactly twice as fast as speed 50? What makes you say that?

Step 5 — Go backward

Flip the direction arrow on both start motor blocks — clockwise becomes counterclockwise and counterclockwise becomes clockwise. Run it.

• Both wheels spun the robot’s-backward direction

Step 6 — Make it agree with itself — and see what happens

Now set both motors to the same arrow — both clockwise. Run it. The wheels are in the air, so watch what would happen on the ground.

If this robot were on the floor, what would it do — and why? (Think about the mirror.)

Hold on to this. It is exactly how you will make the robot spin in place in Project 5.

Step 7 — Plan three of your own

Describe the blocks for each of these. Do not build them yet — just write them.

Now pick one and actually build and run it, to check you were right.

• I tested one of my own commands and it did what I expected

Score It — Checkpoint

No field mission yet — that starts in Project 4. This checkpoint is about whether your motors are set up correctly and whether you can control them on purpose.

My robot’s setup

Write this down. Every program you write from now on depends on it.

Read the program

What will this program do? Write it out before you build it.

My prediction:

Now build and run it. Were you right? If not, what did you miss?

Can you do it again?

• I can tell the motor ports from the sensor ports, and I know a motor works in any lettered port
• I can use the wheel-spin trick to check a motor’s direction without running a program
• I can explain why the two wheels need opposite arrows to drive the robot forward
• I can build a motor block with the right port, arrow, and amount
• I can explain why a start-motor program needs a wait block
• I always finish a start-motor program with stop blocks

Think about it

A teammate says their robot “just doesn’t work” — they run the program and nothing moves. Name two things you would check first, and why.

Nothing in this project told the robot how far to go — only which way to spin and for how long. Do you think that is enough to hit a target on the field? Why or why not?

Next

In Project 4 — Out and Back, the robot comes off the block and onto the field. You will meet the Movement blocks — which handle the mirror for you — drive out of the starting box, park IN THE ZONE, and drive back. And that scores a real mission.