DHT22 Humidity datalogger

There is a large cellar where I could store unused items and documents, but the catch is the humidity there. It is a root cellar near a small brook and the humidity varies between 75% up to 90%.
Archived material should never be exposed to humidity greater than 65%, therefore I have to isolate all documents in boxes from the air of the cellar. But are this boxes safe? Do they keep the humidity away from the documents – even for years?
To have a look into the box environment, I need a data logger. It would be simple to buy one, but much more fun to build one. So a new project is born: I call it the “Data Logger” project.
There are a few phases to realize this project:

  • Prototype (done)
  • Simple Version (in work)
  • Deluxe Version with Display and Case

The Prototype

For the prototype I used a large solder less breadboard from 3M. There I actually just tested the components for the simple version, especially if the protocols are working and if I can use them in the way intended. I will keep this section short and explain everything in detail in the next section. Just to remind you, I tested everything on a breadboard before I soldered the components to a strip board.
DHT22 Humidity datalogger

Parts of The Simple Version

The simple version should be a data logger which automatically starts logging temperature and humidity values it it is powered on. Using a small switch, I can select between logging, reading and erase. In the reading mode, the logger will send all logged values to the serial interface.
Because I need quick results, I will build the whole device using components from Adafruit. Here a list of components I will use for the simple version of the data logger:

These components have an excellent quality. The price today for all the components above is $97. You can buy a similar data logger for approximate $80, e.g. the RHT10 from Extech. Just to make clear this project is more for fun. If you need a cheap solution, better buy a cheap one from Amazon.

There are other components I use which should be available in every electronic lab:

  • Strip board
  • Wires
  • Pin Headers
  • Crimps and Crimp Sockets
  • Switches, DIP Switches, etc.

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