Recently, my bud Vic mentioned that he was having trouble controlling the humidity in his cigar humidor. He had an electric fan over a bowl of water to circulate humidity, but he would have to remember to turn it on or off. Forgetting to turn off the fan meant soggy cigars (perhaps an exaggeration).
So I opened my big yapper and said it would be trivial to automate the fan control. Well, it wasn’t exactly trivial, but was a rather straightforward Arduino design. Nevertheless, perhaps the resulting design will help others.
Vic’s got a bad-ass humidor. It’s got two separate levels and holds many hundred cigars. So we decided it would be best to control the humidity separately in the two levels.
I had on hand a DHT22 humidity/temperature sensor, and most of the required parts. So I downloaded the Adafruit sensor libraries here and here. The second library is specific to the DHT22, but the first library is required too.
Within a few minutes, I had the sensor hooked up and was reading data from it. Easy.
I wanted the unit to be compact, so I chose this small OLED display. These are cheap and look great. They use a I2C interface, so easily connect to the Arduino.
I drive the fans with a couple of 50n06 MOSFETs; overkill for this low-current application, but I had them on hand.
The rest is pretty straightfoward. I put it in a little clear Hammond box (part number 1591CTCL) that I got from Digikey. I love these little boxes – I like to see the guts of the project and don’t need to cut a hole for the display.
And here is the Eagle file: humidor_controller
Here is the source code, in Arduino archive format (zipped too).
A Few More Pictures
Note that it was hard to get a good photo of the OLED display because it is constantly scanning, so aliasing showed up on the rolling-readout camera. The last photo was taken with a long integration time which helped. The display actually looks remarkably crisp in real life!
By the way, check out those sweet pushbuttons. They each have an annular LED that lights when each fan is powered. These are about two bucks a piece from China (seach Ebay for “Green LED Lamp SPST 12mm Panel Mount Momentary Metal Pushbutton Switch T1”).