Buzzer Creation Journal

Total Time Spent: 15.5 Hours

05-24-2025: Planning

Backstory (kinda)

Basically this idea came to me while me and a couple of friends were practicing for a trivia competition that my school's Classics club hosts semi-annually (with other neighboring schools). I realised that many other schools didn't have the funds to buy the official buzzers that all the other schools use, which means that they just end up using some horrible online version, which are very dependent on how good your wifi is. Moreover, these buzzers we're SO HEAVY and annoying to set up that half the time my friends and I didn't even bother practicing because we were too lazy to set up the buzzers and get an actual competition environment going.

What is it?

There will be four buzzer boxes and one main box. Each buzzer box will represent a team (Teams A, B, C, and D) and will have four buttons, one for each player. The main box will house a screen that allows the host to see which player buzzed in first and will also include a reset button to clear all buzzes. For the time being, I plan to include two modes. The first mode allows only one player per team to buzz in, any player from the team can buzz, but only the first buzz from that team will register. The second mode is a free-for-all, where all 16 players can buzz in individually, regardless of their team.

Tech

• All 4 buzzer boxes and the main box will be controlled by an ESP-32 and will communicate with each other using ESPNOW
• All the boxes will be battery powered (now that I type this, I realise that a USB-C port would be nice so that the buzzers have another power source)
• Each buzzer box will have four LEDs that light up depending on which player buzzes in
• For the screen on the main box, it will be a 16x2 LCD with an I2C module

Things Todo

• Deciding if implementing speakers into the main box is feasible
• What type of battery to use (AA or rechargeable)
• Designing the PCB
• Deciding how I want the boxes to look (maybe like an old Mac or just a plain old box to house the electronics)
• Designing the enclosures

Total time spent: 4h

05-25-2025: Circuit Design & BOM

Circuit Design (Changes)

• Implemented 9V power source (stepped down to 5V) and 5V USB-C input, controlled by a SPDT switch
• Added MAX98357A amp, 2 speakers and a micro SD card module (so that the buzzer can actually buzz when a player buzzes in)

BOM (Unfinished)

Item	Purpose	Source	Price
5x ESP32 (38 Pin) Dev Board	Controller
16x2 LCD with I2C Module	Output
Speakers	Output
17x Push Buttons	Input
16x Charger Wires (Any work)	Input
Micro SD Card Module	Input
5x 9V Battery	Power
5x 9V Battery Connector	Power
5x DC - DC Buck Converter	Power
5x 3 Way (SPDT) Switch	Switch
4x Buzzer Box PCB	PCB
1x Main Box PCB	PCB

Things Todo

• Designing the 2 PCBS on KiCAD
• Making the enclosures
• Coding the main and buzzer boxes

Total time spent: 2.5h

05-27-2025: Buzzer Box PCB

KiCAD

• Learned how to use KiCAD for the first time and created the PCB for the buzzer box

Total time spent: 2h

06-04-2025: More Circuit Design

Main Buzzer PCB

• Finished the main buzzer PCB and made sure that the SD module, MAX98357A, and DC-DC buck converter can all fit in the same footprint as the PCB (so it doesn't take up any extra room in the box)
• I didn't bother with silkscreen art for the main box, as both sides have markings that show where the other boards connect to
• The normal buzzer PCBs didn't get silkscreen because I was just too dead to learn it after spending 2 hours trying to figure my way through KiCAD 💀💀💀
• On a separate note, this PCB, I learned how to make custom symbols and footprints (The connectors for the SD card module are on the back of the board on the same side that the 9V battery is going to be on)

Things Todo

• I have to make 2 simple boxes to house the components for both types of boxes
• I have already started on some basic ESP-NOW code to get various boxes working between each other, but I still have to implement the actual buzzer rules
• For the code for the main box, I have to add code to read files from the SD card and play it through the speakers
• Then I can submit my application!!!!!!

Total time spent: 2h

06-10-2025: SUBMITTING AN APPLICATION SPEEDRUNNNNNN!!!!!!

CADing up the Boxes

I used TinkerCAD to make the boxes for the buzzers. I could have done it on something like OnShape, but the design was just a simple box, and there were no special fillets or anything of that sort, so I decided to do it in TinkerCAD (and it just required less critical thinking). List of what I made: - Little handle for the buzzer button - For the normal buzzer boxes, it's just a simple box with 4 holes to allow the buzzer wires to escape and a usb c input, and a 3-way switch - For the main buzzer box, it has a mount for the 16x2 LCD, a hole for a reset button and a usb c input, and a 3-way switch

Programming the Boxes

Since I already have the ESP32's on me, I was able to do most of the coding and semi verify that they work. For the buzzer box code, it was quite simple, as it just sends which buzzer has buzzed to the main box and lights up the corresponding light on the box itself. The main box was slightly more complex as it needed to accept the information that was sent from 4 buzzer boxes and display it on the LCD. Furthermore, the main box also needs to open the .mp3 file from the sd card and play the buzz sound everytime someone buzzes in. I honestly don't know if the whole audio section of the code will work because I have none of the components on hand, but I have looked through countless forums and most people have done audio on an ESP32 in a pretty similar way, so I have hope!!!!!

Total time spent: 5h