This project was based on the need to create a set of "Quiz" buttons for a fun family evening to support a Quiz setting, where multiple teams have to answer quiz questions and you need to know who presses the Quiz-button first.
I bought 4 large pushbuttons on Sparkfun (see https://www.sparkfun.com/products/9181) and mounted the buttons on a piece of bend plexiglass using a glue gun. The Arduino hardware for each button is mounted underneath. (In case you do not own a plexiglass, bender, you can build one yourself using this instruction: https://www.youtube.com/watch?v=-mVmzWQ7Iy8).
Over time I created 3 generations:
- Fully wired - using UTP cable to connect each button to a central Raspberry PI based hub
- Wireless using nRF24L01 radio modules and an AVR based Arduino (Arduino Pro Mini ATMEGA328) using 2.4 Mhz communication
- Wireless using ESP8266 using standard WiFi communication (optional use ESP32 for the quiz hub)
This GitHub repository contains the code for the 2nd and 3rd generation:
- QuizNode - Arduino code for the buttons of the 2nd generation (Arduino Pro Mini ATMEGA328/ nRF24L01 based)
- QuizHub - Arduino code for the central hub of the 2nd generation (Arduino Pro Mini ATMEGA328/ nRF24L01 based with 4 segment display)
- QuizNode8266 - Arduino code for the buttons of the 3rd generation (ESP8266 based)
- QuizHub8266 - Arduino code for the central hub of the 3rd generation (ESP8266 based, using a web interface)
- QuizHubEsp32 - Arduino code for the central hub of the 3rd generation (ESP32 based, using a web interface). This version handles quiz requests more reliable/ honest in the heat of the game due to the faster CPU and improved WiFi connection. So I would recommend going with this version.
Please note you cannot mix 2nd and 3rd generation buttons and hub, as the communication protocol is different.
The quiz button is powered by a single 1,5V battery. The hardware has a voltage booster to create 3.3V working power to the Atmega328 and nRF24L01. Additional power line cleaning is added using a coil and capacitor to ensure the nRF24L01 gets a stable power supply. The large button has a LED and resistor built in that expects a 12V power supply. The Arduino can provide the current directly to the LED, but the resistor needs to be modified to handle the 3.3V power supply.
The quiz hub has a 4-digit 7 segment display to show status and results and uses hardware push buttons to start and stop the quiz questions.
Hardware schematics 2nd Generation
The quiz buttons are ESP8266 based. For the Quiz hub you can choose for the ESP8266 or ESP32. The ESP32 is a better choice as I found this one to be more reliable.
The quiz button is powered by 2 AA batteries making the supply 3V (on average). Since the ESP8266 can not drive directly 20mA to the button LED, I added a current limiting circuit using a single NPN transistor. This requires some manual tuning based on the hFE of the selected transistor. The originzal current limiting resistor that was added to the LED needs to be removed.
The ESP8266 or ESP32 hub is powered by a standard USB connector/ power supply. Gameplay can be activated using buttons or using the web interface of the built-in web server. In the picture below, standard switches are used as buttons. In the ESP32 version the capacitive "Touch" feature of the ESP32 chip is used, so you only need to feed the wires from the "Touch" pins to the outside of your box.
Hardware schematics 3rd Generation
Starting steps:
- Get enough ESP8266 boards (you need 1 for each button) and a board for the hub (ESP32 or ESP8266). I am using the NodeMCU-32S
- Download or clone this repository
- Prepare your Arduino environment for ESP8266 See https://arduino-esp8266.readthedocs.io/en/latest/ and for the ESP32 environment (make sure you have version 1.0.4 or higher) and add this URL to your board manager: https://dl.espressif.com/dl/package_esp32_index.json
Steps for the hub:
- Add any additional MP3 files to the data/sounds folder you may want to play when a quiz button is played
- ESP8266 hub: Install the data upload tool to ensure you can upload the files in the data folder to the ESP8266 you will use as hub. See here and here
- ESP32 hub: Install the data upload tool to ensure you can upload the files in the data folder to the ESP32 you will use as hub. See here
- Upload the data folder to your ESP8266 or ESP32 using the tool above (the root folder should be data folder and the mp3 files are in the sounds subdirectory)
- Compile and upload the QuizHub8266 or QuizHubEsp32 sketch
- Point your phone or laptop to the access point "quizhub" and point your browser to http://192.168.4.1
- Configure your local Wifi network and wait for the quizhub to reboot
- You can now get to the quizhub from your normal Wifi network by pointing your browser to http://quiz.local
Steps for each button:
- Add the circuit to allow measurement of the battery voltage (optional) and current driver for the external LED
- Compile and upload the QuizNode8266 sketch (optionally change the source in case you want to the use the built in LED instead of an external LED)
- Once the button restarts, it will connect to the quizhub WiFi network and ping the server.
When the QuizHub can not connect to the WiFi the Blue LED stays on and the configuration portal is loaded (WiFiManager). You then have to connect to the WiFi network "quizhub" and point your browser to 192.168.4.1 (on most phones this happens automatically). The configuration portal allows you to configure your WiFi parameters:
You can also force the WiFi portal but keeping the Start/Hot button pressed while rebooting.
As soon as a Quiz Node is booted and connected to your configured WiFi, you get to the QuizHub web server by pointing your browser (phone/computer/tablet) to http://quiz.local. The quizhub will also keep the quizhub WiFi up for the nodes. Any new node that boots should show up in the table:
You can assign a name and optional sound to each node by clicking on a row in the table. The configured sound will play through the speakers of the device showing the web site. The team name and selected sound are stored within the browser local storage so the names are kept for your next quiz session. Please note that on IOS (Apple) devices you should play a sound once (manually) by clicking one of the play button before sounds work.
The statistics button allows you to see the battery level of all hubs and various communication statistics:
