Project overview · version 3 · 11 October 2026

Coki-Talkie

A voice message box for small children, with no screen. Four lit buttons, one per grown-up. Hold a button to send that person a voice message; when they answer, their button glows, and a tap plays it.

See the box in 3D, with a live demo

How it works

The message travels through Telegram

The grown-ups use the Telegram app they already have. The box is a Telegram bot, Coki-Talkie for this first box: the child talks to the box, the box sends a voice note, and the adult’s answer comes back the same way. Every step, with the sounds and lights the child gets, is on the 3D page, with a live demo.

Child age 3 and up Coki-Talkie the box Telegram @CokiTalkieBot Adult on their phone holds button, talks voice note plays it answers by voice delivers it waits ≤ 24 h button glows, tap plays it SENDING ANSWERING
The top row is the child sending; the bottom row is the adult answering. If the box is unplugged, Telegram holds new messages for up to 24 hours and delivers them when it’s back.
Outside

What the child sees

to the wall plug, gripped inside status light, on while the box is on paperclip on/off (a pinhole) BACK FRONT adult 1 adult 2: new message adult 3 adult 4 6 cm apart a sticker above each button 4 buttons, one per adult speaker holes microphone holes, far from the speaker
Top view of the lid. Four buttons, 6 cm apart so a toddler’s whole hand lands on one, each with that person’s sticker just above it: a photo, a star, a unicorn, anything the child recognises. All lights are the same white; here the second one blinks because a message is waiting. No screen. At the back, a paperclip in the pinhole switches the box off and on, and a small light shows it’s on. Exact sizes come from the real parts.
Inside

How the parts connect

4 buttons switch + light + ground each 2.8 mm wires Paperclip switch on/off, at the back 40-pin header Raspberry Pi Zero 2 WH the brain: wifi, Telegram, buttons, sound 32 GB memory card, read-only DATA POWER Power supply official, 5.1 V 2.5 A wall plug power data Tiny USB hub plug adapter USB sound card 2 microphones + amplifier speaker, 8 Ω 5 W
One power supply feeds everything: the Pi powers the hub, the sound card and the speaker. The sound card handles both directions: its microphones record the child, and its amplifier plays the answers. The paperclip switch turns the box off and on; the Pi’s own green light, carried to the back wall by a printed light pipe, is the status light.
ButtonSwitch wireLight wire
Adult 1 (left)GPIO 17GPIO 22
Adult 2GPIO 27GPIO 23
Adult 3GPIO 5GPIO 24
Adult 4 (right)GPIO 6GPIO 25
Paperclip switch (back)GPIO 3—

Each button also has two ground wires. No soldering and no tools: ready-made wires clip onto the buttons, and plug-on jumper wires connect them to the Pi’s pins. The pins are a setting in the software, so the enclosure can put the buttons in any order.

Using it

What happens when

Hold a buttonA beep, the light stays on, and it records for up to 60 seconds.
Let goA chime: the box has it. Two quick flashes once it reaches the phone. A slip of under a second doesn’t cut the message.
A button blinksThat person sent a message. A tap plays it.
Tap againReplays their last message, as often as the child wants.
All lights breathe slowlyNo internet. The box is asleep, not broken.
An adult sends text or a photoThe bot replies once a day: voice messages only, please.
Grown-ups: first + last button, 5 sThe box says out loud whether it’s connected to the wifi.
Grown-ups: paperclip in the pinholeSwitches the box off safely; again to switch it on. The small light at the back shows it’s on.
Parts and prices

Shopping list

EU shops only, three orders. The carts are filled and waiting; the Pi is out of stock until about 6 November, so that order waits for it.

PartWhenPrice
BerryBase, Germany
Tiny USB hubConnects the sound card to the Piorder now€3,50
Waveshare USB sound cardMicrophones and speaker amplifierorder now€9,90
Waveshare speaker, 8 Ω 5 WPlays the messagesorder now€5,50
Verbatim 32 GB memory cardHolds the softwareorder now€9,90
Shipping€4,95
Electrokit, Sweden
4 arcade buttons, 30 mm, white lightOne per adultorder now€16,56
Micro switch, 2.8 mm tabsThe paperclip on/offorder now€1,68
Shipping€10,29
Kiwi Electronics, Netherlands
2 × Raspberry Pi Zero 2 WHThe brain; one spare for the next box~6 Nov€41,12
Official Pi power supplyThe one cable to the wall~6 Nov€8,46
Button wire pairs, 2.8 mmClip onto the buttons, no tools~6 Nov€4,83
Jumper wires, 20Connect the button wires to the Pi~6 Nov€4,33
Shipping€6,96
Total, all shipping included€127,98

Includes a spare Pi for the next box. Not included: the enclosure and the stickers.

What happens next

From parts to a working box

  1. Order the BerryBase and Electrokit cartsnow
  2. Test the sound card and speaker on the Mac: microphones and volumewhen the BerryBase parcel arrives
  3. Order the Pi, together with the waiting Kiwi cartaround 6 November
  4. Set up the software and the bot, and assign the four adults to buttonswhen the Pi arrives
  5. Shoebox week: the bare electronics in a box with holes, used for real for a week, to tune the volume, timing and soundsbefore any enclosure
  6. Design and print the enclosure around the measured partsafter the shoebox week
  7. Hand it over to the first family