Some days ago, I received a very weird and exciting SMS from a friend asking me if I wanted the pieces from a “meteorological balloon”. The only words that came to my mind were “What the hell!!??”, so I took my bike and cycled quickly to my friend’s home.
From the outside of the house I was able to distinguish some pieces of a huge latex balloon in the floor. From it, a thin rope climbed to the roof. Mmmm, interesting…
At last, my friend explained me that while he was eating in its garden, a strange thing tied to a parachute hit the floor few meters from him, crashing with violence and breaking into pieces instantaneously. When I went into its garden, I could see what he said to me: A little white box (100x60x150mm approx.) tied to the rope, and pieces of dry carbon batteries everywhere.
Of course, I managed to get it to my home in order to inspect it carefully. First of all I search the Internet for some information: The company is called Vaisala, and makes meteorological sensors and radiosondes. In their web page there was a little note with instructions in case you found a sonde: just throw it in the right place. But that’s not fun!
This model is a Pressure, Humidity and Temperature sensor. It has an autonomy of 1h40′ and may have GPS (I don’t know yet, there are very similar models with and without GPS)
In the first picture you can see the PCB of the sonde: a lot of smd components, a cool antenna (I don’t know what’s its use), an FM antenna and a strap with some sensors. The only one I’ve recognized is the one at the middle.
So, the datasheet says that it’s a Thin film capacitor heated twin sensor, used to measure relative humidity (rH). During the next days I’ll try to get it working (although it seems quite difficult, I don’t like capacitive sensors, too complex for me!)
Inspecting the PCB, I got disappointed when I saw that ALL the big chips were property of Vaisala, and therefore, useless for me. I think that the only components I’m going to reuse are some SMD passives, an LM1117 adjustable power supply and this beauty chip:
As the legend of the picture says, it’s a serial EEPROM 256Kbit memory that can be interfaced with Arduino (link). That is veeery useful combined with some Universal Time Chip, as you can create very cool dataloggers.