Janus Lock

MQTT-controlled garage door automation using an ESP32 and an existing rolling-code remote control.

Janus Lock does not attempt to clone, decode, or bypass the RF protocol. Instead, it electronically simulates a button press on the original remote, preserving the security and reliability of the existing system.

Features

• MQTT-based control
• Supports existing rolling-code remotes
• ESP32-C3 OLED based
• Web-based control UI and configuration
• WiFi provisioning via Access Point mode
• No battery required for the remote
• Compact and low-cost design

Hardware

Component	Details
Microcontroller	ESP32-C3 DevKitM-1
Display	SSD1306 72×40 OLED (I2C)
Relay	CPC1017N Solid State Relay
Relay driver	PC817 4-channel optocoupler isolation module
Boost Converter	XL6009
Remote	Original Garage Remote
Power	USB-C Power Supply

Pin mapping:

Signal	Pin
OLED SDA	5
OLED SCL	6
Door 1 relay	4
Door 2 relay	7
LED	8
Reset button	9

Important — optocoupler module wiring:

The PC817 isolation module ships with a jumper bridging VCC and JD-VCC. Leaving it in place puts relay-coil switching current on the same rail as the ESP32, which causes WiFi/MQTT instability (drops, failed AP broadcast) under load. Remove the jumper and power JD-VCC from a separate 5V source, sharing only GND with the ESP32.

Architecture

MQTT Broker
     |
     v
ESP32-C3  ←→  Web UI (Node.js + Browser)
     |
     v
CPC1017N
     |
     v
Garage Remote
     |
     v
Garage Door

Power Design

USB-C 5V
    |
    +--> ESP32-C3
    |
    +--> XL6009
             |
             +--> 12V Remote Control

MQTT Topics

All topics are prefixed with the configured topicPrefix (default: keremhome).

Topic	Direction	Payload
{prefix}/device/status	Firmware →	online / offline (LWT)
{prefix}/door1/status	Firmware →	ready / triggered
{prefix}/door2/status	Firmware →	ready / triggered
{prefix}/door1/command	→ Firmware	open / press / trigger / 1
{prefix}/door2/command	→ Firmware	open / press / trigger / 1

The MQTT client ID is derived from the device's MAC address (janus-<MAC>), so multiple Janus devices can share the same broker without client ID collisions.

Firmware

Built with PlatformIO.

Dependencies (auto-installed):

• olikraus/U8g2
• tzapu/WiFiManager
• bblanchon/ArduinoJson
• knolleary/PubSubClient

Configuration

On first boot, Janus starts in Access Point mode.

Default configuration portal:

SSID: Janus-Setup
IP:   192.168.4.1

Configuration parameters:

• WiFi SSID / Password
• MQTT Host, Port, Username, Password
• Topic Prefix

Factory reset: Hold the BOOT button for 5 seconds. This works both during normal operation and while the WiFi connect / Janus-Setup AP portal screen is showing.

Web UI

Node.js + Express server serving the control UI. Connects to MQTT directly from the browser over WebSocket for real-time status.

cd web
cp .env.example .env
# Edit .env with your MQTT broker details
docker compose up -d

Available on port 9494.

Why Janus?

Most DIY garage door projects focus on RF cloning or protocol reverse engineering.

Janus takes a different approach:

• Keep the original remote.
• Keep the original security.
• Automate the button press.
• Keep it simple.

Design Philosophy

Simple is the Best

If a feature increases complexity without significantly improving reliability, it probably does not belong in Janus.

Status

🚧 Prototype working

• MQTT communication operational
• Remote triggering operational
• OLED interface operational
• Web UI operational
• Enclosure in progress
• Long-term stability testing in progress

License

MIT License