Monday, September 29, 2014

Decoding Biltema Weatherstation 84086 / sensor 84056

This weather station is sold with one remote sensor and a base station capable of monitoring airpressure. It also have a radio controlled clock.

The remote sensor is capable of measuring temperature and pressure and broadcast this information on the 433 MHz band.

Using a 433 MHz receiver together with a logic analyzer several things could be learned:

The sensor transmit 20 bits of information starting with a 1.45 ms pulse followed by 1.50 ms silence. Pulses 2.16 ms long followed by 0.77 ms silence is '1', and 0.70 ms pulses followed by 2.23 ms silence is representing '0'.

Channel 2, -16.6C, 20% humidity

Several different measurements obtained with varying temperatures and constant humidity (36% (0b100100)) showed that the sensor transmitted the humidity in the seven last bits of the transmission.

The last seven bits is arranged in the following fashion: bit 1, 0 , 6, 5, 4, 3 and 2.

Yeah, and after some googling I found that the decoded signals were presented at

In the following table this decoding is used with the exception of me rotating the bitorder.