From b1639bbecea75dfe98fe1478b6ac43e53c1b16d0 Mon Sep 17 00:00:00 2001
From: Stefan Koelle <stefan.koelle@gmail.com>
Date: Thu, 10 Sep 2026 23:53:19 +0200
Subject: [PATCH] kids rfid player

---
 smarthome/index.njk                  |  4 +++
 smarthome/kids-rfid-player/index.njk | 52 ++++++++++++++++++++++++++++
 stefankoelle/index.njk               |  2 +-
 3 files changed, 57 insertions(+), 1 deletion(-)
 create mode 100644 smarthome/kids-rfid-player/index.njk

diff --git a/smarthome/index.njk b/smarthome/index.njk
index c39975a..1cddb3e 100644
--- a/smarthome/index.njk
+++ b/smarthome/index.njk
@@ -40,6 +40,10 @@ sections:
         summary: "Real-time temperature and humidity monitoring across all rooms with historical charts."
         href: "/air-quality/"
         emoji: "🌡️"
+      - title: "Kids RFID MP3 Player"
+        summary: "Arduino-based audio player for kids using RFID cards, built as a custom alternative to Hoerbert."
+        href: "/kids-rfid-player/"
+        emoji: "🎵"
   - heading: "Personal services"
     cards:
       - title: "iCloud Contacts Sync"
diff --git a/smarthome/kids-rfid-player/index.njk b/smarthome/kids-rfid-player/index.njk
new file mode 100644
index 0000000..e368f53
--- /dev/null
+++ b/smarthome/kids-rfid-player/index.njk
@@ -0,0 +1,52 @@
+---
+title: "Kids RFID MP3 Player"
+section: "smarthome"
+parent: "/"
+description: "A custom Arduino-based RFID audio player for kids, inspired by the Hoerbert and Tonuino projects."
+layout: base.njk
+---
+<h1>Kids RFID MP3 Player</h1>
+<div class="detail-content">
+
+<p>An Arduino-based MP3 player where kids select audio content by holding RFID cards against the device. No screen, no menus, no WiFi — just tap a card and music plays. Built together with my son in 2018 as a cheaper, more flexible alternative to commercial products like the Hoerbert or Tonuino.</p>
+
+<h2>Why this exists</h2>
+<p>Commercial kids' audio players have trade-offs. The Hoerbert only offers 9 direct-select buttons with color-coded cards that aren't very intuitive for very young children. The Tonuino uses expensive RFID figures and relies on WiFi streaming, which introduces latency and dependency on network availability. This project aimed for the best of both worlds: RFID-based content selection with local-only playback, analog volume control, and minimal buttons.</p>
+
+<h2>Hardware</h2>
+<ul>
+<li><strong>Arduino</strong> — the microcontroller running the custom firmware.</li>
+<li><strong>RFID module</strong> — reads MIFARE cards to trigger audio playback.</li>
+<li><strong>DFPlayer Mini</strong> — compact MP3 player module with built-in amplifier, handling audio decoding and playback directly from an SD card.</li>
+<li><strong>Pololu power switch</strong> — handles auto-shutdown to prevent battery drain, replacing a manual toggle switch that a child would forget to turn off.</li>
+<li><strong>Analog volume knob</strong> — a rotary potentiometer for tactile volume control, deliberately chosen over digital buttons.</li>
+<li><strong>3 LEDs</strong> — green (playing), yellow (paused), red (stopped/at end).</li>
+</ul>
+
+<h2>How it works</h2>
+<p>Each RFID card is mapped to a specific audio file on the SD card. Hold a card against the reader and the corresponding story or song starts playing. Hold the RFID keychain against the reader to pause; hold it again to resume. No other buttons exist on the device — the design intentionally minimizes interaction points so even a toddler can use it independently.</p>
+
+<h2>Auto-shutdown behavior</h2>
+<p>The power management distinguishes between two states to avoid unnecessary battery drain:</p>
+<ul>
+<li><strong>Stopped</strong> (playback reached the end) — the device shuts down after 5 minutes.</li>
+<li><strong>Paused</strong> (user paused via RFID) — the device stays on for 1 hour before shutting down, allowing easy resumption.</li>
+</ul>
+
+<h2>The case</h2>
+<p>The enclosure is a custom-built retro-style wooden box, painted by hand. The name "Rocky Box" came from my son, who painted a Paw Patrol character on the front. The design is deliberately quirky and homemade rather than polished — it has character.</p>
+
+<h2>What's missing (by design)</h2>
+<ul>
+<li>No resume after power-off — turning the device off mid-playback means starting the story over from the beginning.</li>
+<li>No skip forward/backward within a track — stories play start to finish.</li>
+</ul>
+<p>Both omissions are intentional. Young children don't need seeking functionality, and keeping the interface to just "tap card, listen" reduces confusion.</p>
+
+<h2>Setup</h2>
+<p>All 100 RFID cards were pre-programmed once and labeled with numbers. No card learning or reprogramming is needed after initial setup — just hand a child a numbered card and they know which story it triggers.</p>
+
+<h2>Code</h2>
+<p>The Arduino firmware is not yet published on GitHub. It's a custom implementation (not Tonuino), written in C++ for the Arduino platform. The code may be uploaded in the future.</p>
+
+</div>
diff --git a/stefankoelle/index.njk b/stefankoelle/index.njk
index 1f75f3c..0987a8b 100644
--- a/stefankoelle/index.njk
+++ b/stefankoelle/index.njk
@@ -80,7 +80,7 @@ layout: stefankoelle.njk
     <li>MP3 Module for playback on attached speaker.</li>
   </ul>
 
-  <h3>Kids RFID MP3 Player (2018)</h3>
+  <h3><a href="https://smarthome.moonweb.org/kids-rfid-player/">Kids RFID MP3 Player</a> (2018)</h3>
   <ul>
     <li>Interactive audio playback system utilizing RFID technology.</li>
     <li>Powered by an Arduino Nano for compact and efficient operation.</li>