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GenAI Kids · Reachy Mini Class 03 / 08 · recap of Class 02
Last time · 6 stations

Pixels → Hand → Robot

1📷

CAMERA

takes a picture

2🟦

PIXELS

2,764,800 numbers

3🔍

FIND HAND

a box around it

4✋

21 DOTS

63 numbers

5📐

CLUES

3 numbers

6🤖

MOTORS

head + antennas

2,764,800→63→3

🧠 Brains that learned

find the hand · mark the 21 dots

📐 Math people wrote

dots → clues → moves

💃 Dance Mirror

same 6 stations · 33 body dots · Reachy copies you

Figure Helix 2.5 = one giant learned brain for a whole robot · Class 02 = eyes 👀 · Class 03 = ears 👂

Live demo · say “Hey Reachy!”

Where’s the Sound?

🗣️

YOU CALL

“Hey Reachy!”

→
👂

4 TINY EARS

hear you

→
🧭

WHICH WAY?

left · front · right

→
🤖

TURN

+ wiggle + nod

Reachy has no eyes on the side of its head. How did it know where you were?
WATCH Call from the left · then from the right
NO RECORDING Reachy only learns a direction
Watch · follow one clap Simulated physics · real speed of sound

Sound = air wiggles

👏 Clap!

Your hands push the air

🌊 Ripples

The push spreads out like ripples in a pond

343 m

every second · about 3 football fields

How sound gets into Reachy · 104 s · no sound track · read along
The sound picture

Voice vs clap

Simulated sound picture of a voice and a clap
SIMULATED · low at the bottom · high at the top · bright = loud

🗣️ Voice

Wiggles with a pattern → stripes like a ladder

👏 Clap

One sharp spike → one tall, thin line

TRY · hum low · then squeak high
Robot ears

A mic turns wiggles into numbers

Simulated wave measured as dots and numbers
SIMULATED · each dot = 1 measurement = 1 number
16,000

measurements every second

👂👂👂👂 4 tiny mics

in a row on Reachy’s head

🧠 Smart chip

Cleans the sound + works out the direction

XMOS XVF3800

Class 02: a picture is just numbers · Class 03: a sound is just numbers too!
How Reachy decides

The closer mic hears it first

Simulated clap reaching four mics one after another
SIMULATED · clap 1 m to the left · mic 3 wins the race
  • 1 · Race: the closest mic hears it first
  • 2 · Tiny gap: about 0.3 ms for a clap 1 m to the left
  • 3 · Angle: the chip turns the gap into a number
0 · LEFT 90 · FRONT 180 · RIGHT Reachy seen from above
Puzzle

Front or behind? It’s a tie!

Simulated: sound from front or behind reaches all four mics together
SIMULATED · front and behind reach all 4 mics at the same time

📏 Mics in a line

Can tell left from right · not front from back

🦉 Owls · 🧒 you

Turn your head · your outer ears help too

So: in our game, sit in front of Reachy
The app · Where’s the Sound?

Call → turn → wiggle → nod

1

LISTEN

4 tiny mics

→
2

DECIDE

which side was first?

→
3

MOVE

turn toward the sound

→
4

WAIT

ignore its own motors

What Reachy does

  • Turns toward you · gently (max 70°)
  • Antenna wiggle + small happy nod
  • Quiet 6 s → back to the middle: “Your turn!”

What the big screen shows

  • The angle + LEFT · FRONT (or behind) · RIGHT
  • Four mics in a row: who heard it first
  • Teacher picks Voice · Clap · Both

No robot mics in the simulator? Press the Pretend Ears buttons: Left · Front · Right

Unplugged · no robot needed

Be the robot: find the clapper

🙈

BLINDFOLD POINTER

Eyes covered · someone claps · point to it!

🤚

COVER ONE EAR

Try again · harder? why?

🏃

EAR RACE

“Left Ear” vs “Right Ear” · who heard first?

Two ears: the closer ear hears it first (and louder). One ear: that clue is gone!
BONUS Clap in front · then behind. Can you tell?
SAFE Eyes covered = stay seated
Game

Find the Caller

REACHY 🙂🙂🙂🙂🙂 “Hey Reachy!” 1.5–2 m
sit in FRONT · remember the puzzle!
  • Teacher points at a caller (shh!)
  • Everyone guesses: where will Reachy look?
  • Caller says “Hey Reachy!”
  • Found you → class point · missed → robot point

CLASS

___

ROBOT

___
Next rounds: whisper vs shout · two callers · sneaky behind
Stretch · if we have time

Ears first, then eyes

👂

HEAR

“Hey Reachy!”

→
🔄

TURN

toward the sound

→
📷

LOOK

camera finds your face

→
🎯

FOLLOW

aims at your nose

👂 Ears

Work all around · even when Reachy can’t see you

👀 Eyes

More exact once you’re in view · same camera trip as Class 02

Camera on only when the class says so
Take home

The closer ear hears it first, and Reachy turns that way.

Class 01

MOVE

Class 02

SEE

Class 03

HEAR
Try at home: eyes closed · point to a family clap · then cover one ear and try again!

Teacher · Zhenhua Yu · Class 03 / 08 · genai4kidz.com