A quick way of keeping the temperature inside an enclosure / greenhouse under control. In my case I had two enclosures, and I used:
- 1 x Arduino UNO board;
- 2x DHT22 temperature / humidity sensors;
- 2x relays;
- 2x hairdryers;
- (optionally) 2x fans (12V) to better circulate the air inside the enclosures.
(please note: the above links are for reference only, and not a recommendation of where to buy it from. Image copyright belongs to their authors / publishers)
In the code (Arduino sketch attached) the lower (heating starts) and higher (heating stops) temperature levels can be set. The code is simple enough, and additional descriptions are included in the comments. The ZIP file also contains the DHT library which needs to be copied in the Arduino IDE library folder (if not already there).
As electricity and humidity do not go well together, I've put a couple of towels at the bottom of each enclosure in order to trap any moisture coming down the sides of the enclosures, and I also wrapped the electric parts of the hairdryers (the handle with the controls) in some plastic film. I also wrapped the relays in some bubble wrap plastic so that the high voltage contacts won't accidentally touch other parts of the system, and damage it.
Please refer to the attached Fritzing diagram for wire connections. The 12V computer fans are connected straight to a 12V power adapter (they run continuously), and are not linked to the Arduino board or the rest of the setup.
UPDATE: I also added a series of LEDs in order to improve the light level. The consumption is of about 6W (1.2 Amps) for the 128 LEDs that I used (assuming a value of 100mW per LED), and it is a much cheaper way of replacing the grow lights. And the cool thing is that they are actually working :-) ... the plants are growing now aiming for the LEDs light. I used RGB LEDs, for which I only connected the Blue and Green colours, leaving the Red pin unconnected. I also used a 5V power adapter, and instead of using resistors (220 ohms) in order to reduce the current, I put two LEDs in series for each 5V connection point.