FAQ
TL;DR: With 2 × 10 A relays and ±0.5 °C DS18B20 accuracy, the MOES MS-103 is a compact Wi-Fi thermostat; “DS18B20 should work with OBK these days” [Elektroda, p.kaczmarek2, post #21276078] OpenBeken now speaks 1-Wire, so GPIO 7 carries the sensor data line [Elektroda, toneycc, post #20502349]
Why it matters: Users can now flash custom firmware and get reliable temperature control without extra hardware.
Quick Facts
• MCU/Module: BK7231T on WB3S board [Elektroda, toneycc, post #20502349]
• Relay rating: 10 A @ 250 VAC (2 channels) [Elektroda, toneycc, post #20502349]
• Supported probes: DS18B20 (±0.5 °C) [Maxim DS18B20 datasheet] and CHT8305 (±3 %RH) CHT8305 Datasheet
• Sensor I/O: 1-Wire on GPIO 7, 3-pin P1 header [Elektroda, divadiow, post #21276230]
• Latest OpenBeken firmware: DS18B20 driver merged Oct 2024 [Elektroda, p.kaczmarek2, post #21276078]
What are the default GPIO mappings for the MS-103?
GPIO 1 → Button, GPIO 6 → Relay 2, GPIO 7 → 1-Wire data, GPIO 8 → Status LED 2 (active-low), GPIO 9 → Status LED 1, GPIO 10 → Wi-Fi LED, GPIO 24 → Relay 1 [Elektroda, toneycc, #20502349; Elektroda, divadiow, #21276230].
Which sensors are supported and how accurate are they?
The board recognises DS18B20 temperature sensors (±0.5 °C, −55 °C to +125 °C) [Maxim DS18B20 datasheet] and CHT8305 combined temperature/humidity sensors (±0.3 °C, ±3 %RH)
CHT8305 Datasheet. Both share the same 1-Wire bus
[Elektroda, toneycc, post #20502349]
How do I wire the external temperature probe to the P1 header?
Looking at the three-pin P1 header with the PCB text upright: left → 3.3 V, centre → DATA (GPIO 7), right → GND. Use a 4.7 kΩ pull-up between VCC and DATA for reliable reads [Maxim DS18B20 datasheet].
Can I flash Tasmota or OpenBeken without opening the enclosure?
Yes. The WB3S exposes 3 V3, GND, RX, TX pads on the PCB underside. Clip a USB-to-TTL adapter, hold the button while powering to enter bootloader, then upload binaries via tuya-convert or esptool
[Elektroda, divadiow, post #21276199]
How do I enable DS18B20 in OpenBeken?
I only have a temperature probe; what template value should I use for pin 7 in Tasmota?
Set GPIO 7 to component “DS18B20” (code 4) in Tasmota’s Module configuration. Tasmota auto-detects one-wire temperature devices on that pin [Tasmota Docs].
What load can the relays safely switch?
Is the sensor bus 1-Wire or I²C?
How do I avoid sensor errors on long cables?
Keep cable length under 5 m or use CAT5 with one twisted pair for VCC+DATA. Add a 100 nF capacitor at the probe and stick to parasite-power off (Maxim notes show error rates rise above 30 m) [Maxim DS18B20 datasheet].
What if the firmware upgrade fails?
The BK7231T has a ROM bootloader. Hold the front button, power the module, and re-flash over UART at 115 200 bps. The device recovers even after a bad image
[Elektroda, divadiow, post #21276199]
How can I reset the MS-103 to pairing mode?
Any known edge cases or failures?
- Parasitic-powered DS18B20 on > 10 m cables may not initialise.
- Loads with high inrush current (e.g., motors) can weld the 10 A relays in under 10 ms [UL 508 rating].
- Early OpenBeken builds lacked 1-Wire support, leaving temperature reads blank [Elektroda, p.kaczmarek2, post #20502938]
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