Microcontroller projects

last updated: 2023-11-15

Use esp32 core version 2.0.14; the alpha versions of 3 have a problem with the neopixel lib

Quick links

Waste bin reminder

I liked the idea of an illuminated waste-bin to remind us to put out the rubbish bins. Meanwhile we have 5 different bins, so the task to remind the day and the bin is not as simple as it was years ago :).

How to get the data

An Excel sheet

A phone call to our municipality revealed that there is no API or other possibility on a server to get the data. The friendly official explained that they work with an Excel sheet, an was kind enough to send me the document by e-mail.

The table had the following format (excerpt):

1 2023-01-11 DEFAULT 1
2 2023-01-25 DEFAULT 1
3 2023-02-08 DEFAULT 1
... ... ...
27 2023-01-12 DEFAULT 1
28 2023-02-09 DEFAULT 1
... ... ...
39 2023-01-03 DEFAULT 1
40 2023-01-17 DEFAULT 1

A little PHP

Next I needed a PHP script to convert the data to a JSON stream. I used an older script to retrieve the data called SimpleXLSX.php (version 0.8.23) from the Excel sheet. Thanks to Sergey Shuchkin. Newer versions can be found on his github page: https://github.com/shuchkin/simplexlsx, but they will not work with the following script.

With the help of Bob Fisch (https://www.fisch.lu/) I cooked a script to do the job:

      header('Content-Type: text/json');

      // include library to ready XLSX
      include 'SimpleXLSX.php';

      // define what file to load

      // open the file
      if($xlsx=SimpleXLSX::parse($IMPORT)) {
        /*echo '<pre>';
        print_r( $xlsx->sheetNames() );
        print_r( $xlsx->sheetName( $xlsx->activeSheet ) );
        print_r( $xlsx->rows(1) );
        echo '</pre>';

        // get name of cols of sheet #1 (Tours)
        foreach($rows[0] as $key=>$value) {
        //echo '<pre>'.print_r($cols,true).'</pre>';

        $data = array(array());

        for($i=0; $i<count($rows); $i++) {
          if (($rows[$i][$cols['MENAGERS']])=="1") {
            $data[substr($rows[$i][$cols['DATE']],0,10)] = 'waste';
          else if (($rows[$i][$cols['ORGANIQUES']])=="1") {
            $data[substr($rows[$i][$cols['DATE']],0,10)] = "biomass";
          else if (($rows[$i][$cols['VERRE']])=="1") {
            $data[substr($rows[$i][$cols['DATE']],0,10)] = "glas";
          else if (($rows[$i][$cols['PAPIER']])=="1") {
            $data[substr($rows[$i][$cols['DATE']],0,10)] = "paper";
          else if (($rows[$i][$cols['VALORLUX']])=="1") {
            $data[substr($rows[$i][$cols['DATE']],0,10)] = "valorlux";
          else if (($rows[$i][$cols['ENCOMBRANTS']])=="1(SD)") {
            $data[substr($rows[$i][$cols['DATE']],0,10)] = "bulky_waste";
            $void = array_shift($data);
        echo json_encode($data);
      else {
        echo '{"error":"file not found"}';      // error in JSON format

You find everything on github. Save the script as index.php together with the SimpleXLSX.php script and the excel file in a folder of your server, and you can access the data. You find everything on github.

Look on https://www.weigu.lu/waste_collection/index.php



The hardware consists of a microcontroller board and some plastic :).



I choose a Lolin C3 mini board with an RISC-V core because I love the idea and an open standard instruction set architecture and because of the integrated WS2812B RGB LED.

waste bin

3D print

The Luxemburgish bins look like the one I found on thingiverse from Stephen Miles (Thanks).

waste bin

I had to add a hole to the bin body for my USB-C connector and did this in FreeCAD. But then I remarked there where problems with the stl from Stephen. So I grabbed the original file from Wojciech Madej (also Thanks :)) and stretched it to 100 mm height.

I used black PLA for the wheels and Felix Glas filament for the body and lid.

You find the Freecad and stl files on github.


I used my ESP Toolbox library and so we get OTA and logging via UDP. The data is also sent via MQTT to an MQTT server. In the config.h file (comment #define USE_SECRETS) or the secrets_waste_bin_reminder.h file in a Secrets folder inside your library folder you can change the important data like your password.

More infos: ESP Toolbox library

      Hardware used: Lolin C3 Mini
      for UDP, listen on Linux PC (UDP_LOG_PC_IP) with netcat command:
      nc -kulw 0 5558
      more infos: www.weigu.lu/microcontroller/esptoolbox/index.html
      Copyright (C) 2023 Guy WEILER www.weigu.lu

      This program is free software: you can redistribute it and/or modify
      it under the terms of the GNU General Public License as published by
      the Free Software Foundation, either version 3 of the License, or
      (at your option) any later version.

      This program is distributed in the hope that it will be useful,
      but WITHOUT ANY WARRANTY; without even the implied warranty of
      GNU General Public License for more details.
      You should have received a copy of the GNU General Public License
      along with this program.  If not, see <https://www.gnu.org/licenses/>.

    /*!!!!!!       Make your changes in config.h (or secrets_xxx.h)      !!!!!!*/

    /*------ Comment or uncomment the following line suiting your needs -------*/
    #define USE_SECRETS
    #define OTA               // if Over The Air update needed (security risk!)
    //#define MQTTPASSWORD    // if you want an MQTT connection with password
    #define STATIC            // if static IP needed (no DHCP)

    /****** Arduino libraries needed ******/
    #include "ESPToolbox.h"            // ESP helper lib (more on weigu.lu)
    #ifdef USE_SECRETS
      // The file "secrets_xxx.h" has to be placed in a sketchbook libraries
      // folder. Create a folder named "Secrets" in sketchbook/libraries and copy
      // the config.h file there. Rename it to secrets_xxx.h
      #include <secrets_waste_bin_reminder.h> // things you need to change are here
      #include "config.h"              // or things you need to change are here
    #endif // USE_SECRETS
    #include <PubSubClient.h>          // for MQTT
    #include <ArduinoJson.h>           // convert MQTT messages to JSON
    #include <WiFiClientSecure.h>
    #include <HTTPClient.h>
    #include <Adafruit_NeoPixel.h>

    /****** WiFi and network settings ******/
    const char *WIFI_SSID = MY_WIFI_SSID;           // if no secrets, use config.h
    const char *WIFI_PASSWORD = MY_WIFI_PASSWORD;   // if no secrets, use config.h
    #ifdef STATIC
      IPAddress NET_LOCAL_IP (NET_LOCAL_IP_BYTES);  // 3x optional for static IP
      IPAddress NET_GATEWAY (NET_GATEWAY_BYTES);    // look in config.h
      IPAddress NET_DNS (NET_DNS_BYTES);
    #endif // ifdef STATIC
    #ifdef OTA                                      // Over The Air update settings
      const char *OTA_NAME = MY_OTA_NAME;
      const char *OTA_PASS_HASH = MY_OTA_PASS_HASH; // use the config.h file
    #endif // ifdef OTA

    IPAddress UDP_LOG_PC_IP(UDP_LOG_PC_IP_BYTES);   // UDP log if enabled in setup

    /****** MQTT settings ******/
    const short MQTT_PORT = MY_MQTT_PORT;
    WiFiClient espClient;
    PubSubClient MQTT_Client(espClient);
      const char *MQTT_USER = MY_MQTT_USER;
      const char *MQTT_PASS = MY_MQTT_PASS;
    #endif // MQTTPASSWORD

    Adafruit_NeoPixel pixels(NUMPIXELS, PIXEL_PIN, NEO_GRB + NEO_KHZ800);

    ESPToolbox Tb;                                // Create an ESPToolbox Object

    /****** SETUP ****************************************************************/

    void setup() {  
      Tb.set_udp_log(true, UDP_LOG_PC_IP, UDP_LOG_PORT);  
      #ifdef STATIC
        Tb.set_static_ip(true,NET_LOCAL_IP, NET_GATEWAY, NET_MASK, NET_DNS);
      #endif // ifdef STATIC
      MQTT_Client.setServer(MQTT_SERVER,MQTT_PORT); //open connection MQTT server
      #ifdef OTA
        Tb.init_ota(OTA_NAME, OTA_PASS_HASH);
      #endif // ifdef OTA    
      Tb.log_ln("Setup done!");

    /****** LOOP *****************************************************************/

    void loop() {  
      #ifdef OTA
      #endif // ifdef OTA
      if (Tb.non_blocking_delay(PUBLISH_TIME)) { // PUBLISH_TIME in config.h
        which_bin = get_waste_bin_info_from_server();
        if (which_bin!="no_info") {
          Tb.log("Which bin to use: " + String(which_bin) + '\n');
          Tb.log("Waiting some time before the next round...\n");
      if (WiFi.status() != WL_CONNECTED) {   // if WiFi disconnected, reconnect
      if (!MQTT_Client.connected()) {        // reconnect mqtt client, if needed
      MQTT_Client.loop();                    // make the MQTT live
      delay(10); // needed for the watchdog! (alt. yield())

    /********** MQTT functions ***************************************************/

    // connect to MQTT server
    void mqtt_connect() {
      while (!MQTT_Client.connected()) { // Loop until we're reconnected
        Tb.log("Attempting MQTT connection...");
        #ifdef MQTTPASSWORD
          if (MQTT_Client.connect(MQTT_CLIENT_ID, MQTT_USER, MQTT_PASS)) {
          if (MQTT_Client.connect(MQTT_CLIENT_ID)) { // Attempt to connect
        #endif // ifdef MQTTPASSWORD
          Tb.log_ln("MQTT connected");
        else {
          Tb.log("MQTT connection failed, rc=");
          Tb.log_ln(" try again in 5 seconds");
          delay(5000);  // Wait 5 seconds before retrying

    // MQTT get the time, relay flags ant temperature an publish the data
    void mqtt_publish() {
      DynamicJsonDocument doc_out(1024);
      String mqtt_msg, we_msg;
      doc_out["datetime"] = Tb.t.datetime;    
      //doc_out["date"] = Tb.t.date;    
      //doc_out["tomorrow"] = Tb.t.tomorrow;  
      doc_out["waste_bin"] = which_bin;  
      serializeJson(doc_out, mqtt_msg);
      Tb.log("MQTT published at ");

    /********** HTTPS functions **************************************************/

    String get_waste_bin_info_from_server() {
      String json_payload;
      DynamicJsonDocument http_doc(4096);
      String which_bin;
      int http_code;
      WiFiClientSecure *Wifi_s_client = new WiFiClientSecure;
      if(Wifi_s_client) {
        Wifi_s_client->setInsecure();   // set secure client without certificate    
        HTTPClient Https; //create an HTTPClient instance
        if (Https.begin(*Wifi_s_client, server_name)) {  // HTTPS      
          http_code = Https.GET(); // start connection and send HTTP header          
          Tb.log("[HTTPS] GET... code: " + String(http_code) + '\n');
          if (http_code > 0) { // httpCode will be negative on error              
            if (http_code == HTTP_CODE_OK || http_code == HTTP_CODE_MOVED_PERMANENTLY) {
              json_payload = Https.getString(); // file found         
              deserializeJson(http_doc, json_payload);
              if (Tb.t.hour > 11) {
                which_bin = String(http_doc[Tb.t.tomorrow]);
              else {
                which_bin = String(http_doc[Tb.t.date]);
            else {
              Tb.log("[HTTPS] GET... failed, error: " +  String(http_code) + '\n');
          else {
            Tb.log("[HTTPS] Unable to connect\n");
            return "no_info";
        return which_bin;

    /****** NeoPixel functions ***************************************************/

    void init_pixels() {
      pixels.begin(); // INITIALIZE NeoPixel strip object (REQUIRED)
      pixels.clear(); // Set all pixel colors to 'off'  

    void show_pixels() {
      unsigned int my_delay = 250; 
      pixels.clear(); // Set all pixel colors to 'off'  
      pixels.setPixelColor(0, pixels.Color(255, 255, 255)); // white
      delay (my_delay);
      pixels.setPixelColor(0, pixels.Color(165, 22, 22)); // brown
      delay (my_delay);
      pixels.setPixelColor(0, pixels.Color(0, 255, 0)); // green
      delay (my_delay);
      pixels.setPixelColor(0, pixels.Color(0, 0, 255)); // blue
      delay (my_delay);
      pixels.setPixelColor(0, pixels.Color(125, 0, 125)); // light blue
      delay (my_delay);
      pixels.setPixelColor(0, pixels.Color(255, 255, 0)); // yellow
      delay (my_delay);
      pixels.setPixelColor(0, pixels.Color(0, 0, 0)); // off  
      delay (my_delay);  

    void set_wastebin_color(String which_bin) {
      if (which_bin == "waste") {
          pixels.setPixelColor(0, pixels.Color(255, 255, 255)); // white      
      else if (which_bin == "biomass") {
          pixels.setPixelColor(0, pixels.Color(165, 22, 22)); // brown      
      else if (which_bin == "glas") {
          pixels.setPixelColor(0, pixels.Color(0, 255, 0)); // green      
      else if (which_bin == "paper") {
          pixels.setPixelColor(0, pixels.Color(0, 0, 255)); // blue      
      else if (which_bin == "valorlux") {
          pixels.setPixelColor(0, pixels.Color(125, 0, 125)); // light blue      
      else if (which_bin == "bulky_waste") {
          pixels.setPixelColor(0, pixels.Color(255, 255, 0)); // yellow      
      else if (which_bin == "null") {      
          pixels.setPixelColor(0, pixels.Color(0, 0, 0));