Coki-Talkie · the box in 3D · sketch · 11 October 2026

Coki-Talkie

A CokisLab project

A voice message box for small children, with no screen. Each of the four buttons belongs to one grown-up: hold it to send them a voice message, and when they answer, their button blinks and a tap plays it. The grown-ups use Telegram on their phones.

Below: the box from seven angles with every part in place (drag to turn it), next to everyday objects for scale, a child’s hand at real size, a live demo, and every step of how it works. The teal parts are the ones Paco prints; everything else is bought.

Project overview: the parts, how they connect, and the prices

View
Child’s hand, real size
Labels
Live demo about 30 seconds: pressing, the sounds, the phone and the reply
drag to turn · click, then scroll or pinch to zoom

From the front

How it works

From setting it up to the first “hello”

Every step, on the box and on the grown-up’s phone, with the sound or light the child gets at each moment.

1 · Setting it up, once

  1. Javi
    Creates the box’s own Telegram bot. This first box’s is called Coki-Talkie; every box gets its own.
  2. Grown-up’s phone
    Each grown-up gets a link from Javi, opens it in Telegram, taps Start and sends any message, like “hi”. Telegram is free; that’s all they install.
  3. Javi
    Gives each grown-up a button and puts a sticker for them above it: a photo, a star, a unicorn, anything the child recognises.
  4. Box
    Joins the home wifi. While it’s on, the small light at the back is on.

No phone numbers are shared. The box only knows four Telegram chats, never a number. It listens to those four people only and ignores messages from anyone else. Each grown-up has a private chat with the box and doesn’t see the others’ messages.

2 · The child sends a message

  1. Child
    Holds the button under Mama’s sticker. beepbutton lights up Meaning: talk now.
  2. Child
    Talks, up to a minute, still holding. If the finger slips off and comes back within a second, it’s still one message.
  3. Child
    Lets go. chime The box has the message.
  4. Box
    Sends it over the wifi. two quick flashes It has arrived.
  5. Grown-up’s phone
    A normal Telegram notification from Coki-Talkie: a voice message in the child’s own voice. Tap to listen.

If something’s off: a press shorter than about half a second gets a soft blip and nothing is sent. If there’s no internet, a low “uh-oh” sound plays once; the box keeps trying and sends it as soon as the internet is back.

3 · The grown-up answers

  1. Grown-up’s phone
    In the same chat, holds Telegram’s microphone button and records a reply, like any voice message.
  2. Box
    A few seconds later, that person’s button starts to blink. button blinks No sound, so it never wakes a sleeping child.
  3. Child
    Taps the blinking button. The message plays out loud and the blinking stops. With several messages waiting, each tap plays the next one.
  4. Child
    Taps again to hear it again, as often as they like. It stays until that person sends a new one, or the box is switched off.

If something’s off: text, photos or stickers don’t reach the box; the bot replies “voice messages only”, at most once a day. If the box is off or offline, Telegram keeps the messages for 24 hours and delivers them when it’s back.

Grown-ups only

  1. At the back
    A paperclip in the pinhole switches the box off safely; again to switch it on. The small light at the back shows it’s on. Unplugging is safe too.
  2. On the lid
    Hold the first and last buttons for 5 seconds: the box says out loud whether it’s connected to the wifi.
  3. Box
    All four buttons breathing slowly means no internet: it’s waiting, not broken.
  4. Parents’ phones
    Parents can set a daily limit of messages, quiet hours (for example 20:00–07:00) and get a copy of every message, just by writing to the box in Telegram. Typing “/” shows the menu, and “help” explains everything. All off until a parent switches it on.
  5. Javi
    Can update the box’s software remotely, to fix a problem or add an improvement, so it never has to come back. The box only ever records while a button is held.

Sounds and lights at a glance

What the child hears or seesWhat it means
beep and the button lights upRecording: talk now
chimeThe box has the message
two quick flashesThe message reached the phone
soft blipToo short to send, or nothing to play
low “uh-oh”Couldn’t send yet; it keeps trying
a button blinkingA new message from that person
all buttons breathing slowlyNo internet
light at the backThe box is on

Printed by Paco

  • Box and lid, with 4 button holes, a frame for each sticker, the speaker grille and the microphone holes
  • Tray for the Raspberry Pi
  • Clips that hold the speaker under the lid
  • Posts that hold the sound card under the lid
  • Grip that holds the cable where it leaves the box
  • Holder for the paperclip switch, right behind its pinhole
  • A short light pipe (clear filament) that carries the Pi’s green light to the back wall

Bought

  • Raspberry Pi Zero 2 WH, with its memory card
  • Official power supply and its cable
  • USB sound card with 2 built-in microphones
  • Speaker, 8 Ω 5 W, 100 × 45 × 21 mm
  • Small USB hub
  • 4 arcade buttons with a white light, 30 mm
  • Micro switch for the paperclip on/off
  • Button wires and plug-on jumper wires

This is a sketch, not a drawing to print from. The box here is about 26 × 16 × 7.5 cm, sized around the parts, with the buttons 6 cm apart. The speaker, buttons and switch use the shops’ measurements; the sound card, hub, wires and the hands are estimates (average sizes for each age). Paco designs from the real parts once they arrive.