Weather Station Part I

 For those who have the Thermor/BIOS model BW951/THYDG990R(see image), like me, probable are frustrated at the wireless interface/battery life. Also the Main unit has no way of recording over time. So, here is me hacking the sensors with the intention of being able to monitor the current conditions through a PC/MediaCenter.
    This is a work in progress, and new material will be added as it progresses.


The BW951 comes with the Receiver Unit, Transmitter Unit, Rain Gauge,  and Anemometer. Other models seem to use the same sensors, so these hacks should work on them as well.






 First order of business was to get data from the anemometer. Given the fact that it interfaces to the transmitter unit with a 4 wire phone jack, and that 2 of them are power and ground, sending wind speed and direction on 2 wires meant that there would be some electronics in the unit.
 After removing the 3 screws holding the 2 halves together, and carefully prying them apart you see the circuit board.

    -I mean carefully, because if it pops, you can tear out the wires that attatch the magnetic wind sensor -
- from the board (which I did) -



 Here is an image of the circuit board in the sensor. The two yellow wires attatch to the magnetic sensor for wind speed. All the other wires were added by me. I have removed the crystal for the microcontroller in order to keep it "dead" and decativate all the lines coming from it. It was located near SW1 (left side) on the board.

 The connections are as follows:
- Brown: Wind Speed
- Grey   : Enable Sensors (described below)
- Red    : +Vcc (3.3V)
- Black  : Ground
- Others: Purple, Green, Blue, Orange 4bit output of position.
- Take note of where the grey wire is attatched. That side of the resistor goes directly to the transistor. I was unable to solder it to the other side of the resistor because of the encapsulting material on the microcontroller. Be sure to add a 1K resistor to the signal line! -
Below is the schematic of the used parts of the sensor.

    You can see from this schematic that in order to measure the wind direction,and speed, the enable line must be high. This is done for a power savings. With the enable line low, no power is consumed by the sensing parts, in addition it also controls power to the leds used by photo-transistors, also for power savings.

    Now we need to attatch these points onto a new microcontroller that we can control. The PIC series of microcontroller will be just perfect for this. I have chosen the PIC16F628, but others with enough pins to do all the monitoring will work as well, just ensure that it has a UART on board. The next update will contain a schematic and code in order for us to monitor wind speed, direction, temperature, and rainfall.
           

- To be Continued -

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