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.
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:
| Version | Status |
|---|---|
| Firmware v0.3 | Event-tested release, replaced by v0.3.1 bug-fix update |
| PCB v0.1 | Manufactured, functional through the web UI, but has known display issues |
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.
- 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
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.
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.
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.
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.
Start here:
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
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 documentation is in the docs folder.
Current files include:
docs/BOM.xlsx
docs/BOM.csv
docs/Wiring_schematic.pdf
docs/build-guide.md
The KOTH Timer now has a tested PCB revision.
| PCB revision | Status | Recommendation |
|---|---|---|
v0.1 |
Manufactured and functionally usable through the web UI, but has known TM1637 display reliability issues | Reference only / not recommended for new builds |
v0.2 |
Manufactured, assembled, and tested with no known faults | Recommended PCB revision |
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 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.
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:
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.
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.
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.
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
This project is released under the MIT Licence.