Sonoff RFR3 DIY — 433 MHz MQTT gateway mod

Source

• Type: webpage
• Origin: https://vivio.wordpress.com/2020/04/23/sonoff-rfr3-433-mqtt-gateway-mod/
• Imported: 2026-05-10

Content

Context

The author wanted a UV-C lamp control setup with:

1. Start the lamp from a remote
2. Turn the lamp off if a PIR sensor or door opens
3. Prevent turning the lamp on unless PIR and door are closed

Wi-Fi was kept for monitoring only (unreliable router). Intended signal path: PIR2 / remote / door sensor → RF Bridge → RFR3 relay.

Limitation: The Sonoff RF Bridge can learn RF sensors and send RF to the relay, but simple RF did not expose relay state reliably. The Sonoff RFR3 DIY has Wi-Fi and RF but is not a stock RF gateway. The goal was an RF gateway with a relay that can decode RF sensor traffic and expose relay state.

Credits and references:

• DrFragle and MrShark — discussion on Scargill’s blog (Sonoff RF Bridge)
• Inspired by 1 TECHNOPHILE — New Sonoff RFR3 as 433ToMQTT gateway

Flash Tasmota

• Flash Tasmota on the Sonoff RFR3 DIY. The author notes that eWeLink app firmware 3.5 broke DIY mode; USB-to-UART at 3.3 V was required for flashing.
• Use the tasmota-sensors.bin build from Tasmota releases (full sensor build).

Hardware modification (RF chip)

On the board, desolder the SMD resistor on the RF chip side and solder a wire to the terminal described in the TECHNOPHILE article. TECHNOPHILE suggests cutting a copper trace; the author removed the resistor entirely as cleaner.

GPIO choice: TECHNOPHILE uses GPIO4, which the author found hard to solder. Digiblur used GPIO1 as input (ESP TX pin on their diagram). The author soldered GPIO1 for easier access.

Enclosure: The extra wire can stop the PCB from sitting flat in the bottom shell and block the tall switch in the top shell — the author slightly enlarged a hole in the upper shell so the assembly fits.

Tasmota configuration

From Tasmota Discord (thanks to barbudor, Seth, squalazzo): after this mod you cannot use the stock Sonoff RF bridge template on the RFR3. Use RC-Switch behavior by assigning the GPIO wired to the RF receiver as RF Recv (106).

Because the author wired GPIO1, in Configuration → Configure Module set GPIO1 to RF Recv (106).

After saving, the Console should show RF reception alongside relays.

Notes

• One-off issue: after a full power cycle, the relay once came up on; could not reproduce.

Safety: Original post includes UV-C and mains safety disclaimers — follow electrical and UV safety practices.

Key Takeaways

• Sonoff RFR3 can be modded (RF chip resistor removal / reroute + wire) to act as a 433 MHz receive path into Tasmota, similar in spirit to the RF Bridge + MQTT gateway approach.
• Prefer tasmota-sensors.bin for this use case; flash via UART if eWeLink/DIY mode is broken.
• Use RF Recv (106) on the GPIO you actually soldered (author used GPIO1 instead of GPIO4 for easier soldering).
• Expect to adjust the case so internal routing does not jam the mechanical switch.