Nerf timer

KOTH-Timer

A DIY Arduino Nano ESP32 King of the Hill timer for Nerf, foam flinging, skirmish games, and objective-based events.

KOTH-Timer is an open-source physical game timer with arcade buttons, TM1637 displays, battery monitoring, and a local phone-friendly referee/admin web interface. It is designed for two-team King of the Hill games where players physically hold a button to capture the objective.

This project is based on a working timer that has been tested successfully at local Nerf events. A few people in the hobby scene asked how to build their own, so this repo exists to make that possible.

The goal is to keep it practical, buildable, and easy to modify.

Current Recommended Versions

The current recommended firmware release is:

v0.3.1

v0.3.1 is the recommended firmware for new builds.

It keeps the tested v0.3 phone/referee UI and adds small UI input fixes so team colours and match duration can be edited more reliably from the web interface.

Recommended PCB revision:

v0.2

PCB v0.2 has been manufactured, assembled, and tested with no known faults. It is the recommended PCB revision for new builds.

The tested KOTH Timer PCB v0.2 project is available on PCBWay for convenience if you choose to use them:

Order / view the KOTH Timer PCB v0.2 project on PCBWay

Older versions remain available for reference but are not recommended for new builds:

What It Does

KOTH-Timer is a physical objective timer for two-team King of the Hill style games.

Players press their team’s button to capture the objective. The timer tracks control time and shows the game state through:

• Large physical displays
• Button LED feedback
• A local referee/admin web interface

The timer runs locally from the ESP32, so it does not need internet access during gameplay.

Prototype Photos

Finished Prototype

Inside Wiring

Custom PCB

Features

• Two-team King of the Hill timer
• Physical arcade button controls
• LED button feedback
• Four TM1637 4-digit display modules
• Local ESP32-hosted web interface
• Phone-friendly referee/admin controls
• Configurable match duration
• Configurable team colours
• Battery voltage display
• Pause and resume controls
• Reset lockout to prevent accidental resets
• Game-over winner display
• Live referee time adjustment during gameplay
• Open Wi-Fi network by default for quick event setup
• Optional Wi-Fi password support
• No internet required during gameplay

Referee/Admin Connection

The timer creates its own local Wi-Fi network.

SSID: KOTH-Timer
Password: none / open network

After connecting, open:

http://10.10.10.1

Connection test page:

http://10.10.10.1/ping

Some phones may warn that the network has no internet. This is normal. Choose the option to stay connected or use the network anyway.

Optional Wi-Fi Password

The Wi-Fi network is open by default so referees can connect quickly during events.

If you want to add a password, edit the firmware near the top of the code.

Find:

static const char* AP_PASS = "";

Change it to a password with at least 8 characters:

static const char* AP_PASS = "kothtimer";

Then upload the firmware again.

Who This Is For

This project is for hobbyists who want to build their own objective timer for games such as:

• Nerf events
• Foam flinging games
• Gel blaster games where legal
• Airsoft-style objective games where legal
• Backyard or club-based capture games
• Custom scenario games

You do not need to be an expert programmer, but you should be comfortable with basic wiring, soldering, and flashing an ESP32.

Basic Hardware Needed

The current build uses:

• Arduino Nano ESP32
• 18650 Li-ion cell
• 18650 battery holder
• 5 V boost converter
• Fuse
• Rocker power switch
• 2 large arcade buttons with LEDs
• 4 TM1637 4-digit display modules
• 5-segment battery indicator
• Battery display button
• Resistors
• Wire
• Enclosure
• USB cable for flashing
• Basic soldering tools

See the docs folder for the BOM, schematic, and full build guide.

Build Guide

Start here:

Build Guide

The build guide covers:

• Parts required
• Tools required
• Power wiring
• Arduino Nano ESP32 pinout
• Button wiring
• Display wiring
• Battery indicator wiring
• Firmware upload
• Wi-Fi connection
• Event-day testing
• Troubleshooting

Firmware

The firmware is written for the Arduino Nano ESP32 using the Arduino IDE.

Current recommended firmware:

Firmware/KOTH_Timer_v0_3_1/KOTH_Timer_v0_3_1.ino

For Arduino IDE compatibility, the .ino file should be inside a folder with the same name as the sketch.

Hardware Files

Hardware documentation is in the docs folder.

Current files include:

docs/BOM.xlsx
docs/BOM.csv
docs/Wiring_schematic.pdf
docs/build-guide.md

PCB Hardware Status

The KOTH Timer now has a tested PCB revision.

PCB v0.1

PCB v0.1 was the first manufactured PCB revision.

It is functional through the web UI, but some TM1637 displays may show interference, flicker, incorrect segments, or unstable output.

The v0.1 files are kept in the repo for reference, troubleshooting, and comparison, but new builders should use PCB v0.2 instead.

PCB v0.2

PCB v0.2 is the current recommended PCB revision.

It was redesigned based on lessons from v0.1, with improvements around display reliability, local display decoupling, and cleaner TM1637 signal routing.

PCB v0.2 has been manufactured, assembled, and tested with no known faults.

Supported By PCBWay

PCB manufacturing for newer KOTH Timer PCB revisions has been supported by PCBWay.

PCBWay helped support this open-source hardware project by providing PCB manufacturing support while allowing the firmware, design files, known issues, and documentation to remain open source.

Their support made it easier to test real PCB revisions, improve the board design, and share the results back with other builders.

You can check out PCBWay’s PCB manufacturing and assembly services here:

PCBWay

The tested KOTH Timer PCB v0.2 project is available on PCBWay here:

Order / view the KOTH Timer PCB v0.2 project on PCBWay

Thanks to PCBWay for supporting open-source hardware creators and helping this project move from a hand-wired prototype to a tested PCB-based build.

Note: PCBWay supported manufacturing for this project, but the design notes, testing results, known issues, and recommendations in this repository are written independently.

Future Development

Planned future work may include:

• Improving hardware documentation
• Adding more photos and wiring diagrams
• Adding extra game modes beyond King of the Hill
• Improving the referee/admin interface based on event feedback
• Exploring a Bluetooth or app-based version if there is enough interest

The v0.3.1 firmware is the current recommended release. It is based on the event-tested v0.3 firmware and includes additional web-interface input fixes.

PCB v0.2 has been manufactured, assembled, and tested with no known faults and is the current recommended PCB revision.

Project Status

This is a hobby project, not a commercial product.

The current firmware has been tested at an event, but builders should still test their own wiring and setup before using the timer in a game.

If you build one, feel free to modify it for your own event rules, enclosure, buttons, battery setup, or game style.

Related Uses

This project may be useful for:

• Nerf King of the Hill games
• Foam flinging objective games
• DIY skirmish game timers
• Arduino ESP32 game props
• Capture point timers
• Referee-controlled event timers
• Local Wi-Fi game control panels

Licence

This project is released under the MIT Licence.