Remote keyless entry for garage door
- The Hörmann HS 5 868-BS remote is too heavy.
- When you forget the remote, you can't open the garage door from the outside.
Design files in EasyEDA
A light-weight remote has been developed. It contains :
- An RFM95W-868S2 LoRa transceiver : set to minimal TX-power, uses very little current.
- ESP-C3-13U-4M module : available and easy to solder, and includes wifi (not used on the remote).
The controller is mounted near the Hörmann garage door controller, inside the garage. It consists of:
- The same PCB transceiver as in the remote (RFM95 + ESP-C3). So that design only needed to be done once.
- A 24V to 5V power PCB. This PCB has an over-sized power supply so that it can also be used in other projects, e.g. for powering a Raspberry Pi.
- This design was more of an exercise in power supply design than being really practical.
- Much smaller supplies exist (TPSM84209).
- If you're after the least effort, then use an 7805 or one of its switching drop-in replacements.
- A wifi-antenna, connected to the ESP-C3-13U-4M module.
The controller is mounted near the opening of the garage door to increase wireless range. A 3m UTP-cable connects to an RJ45-terminal socket adapter from Adafruit or AliExpress, which makes connection to the terminal blocks of the Hörmann garage door interface.
Authentication is based on Kryptoknight which is based on a shared secret key between both parties. It's a light-weight protocol that could also be used on 8-bit MCUs. This protocol is not vulnerable to rolljam attacks, which is a problem in rolling code schemes commonly used for this application.
The controller also includes a web-interface. By browsing to its fixed local IP-address, a webpage on your smartphone opens. If you type the correct pin code, the garage door will open. Security of this web-interface relies on the secrecy of your wifi password and the secret pin.