Greenhouse / Enclosure Automatic Heating




About: Passionate about computers and stuff :-)

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.

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    5 Discussions


    1 year ago

    Interesting. I have a greenhouse made from enforced polystyrene (the kind used as isolation in construction), but I also have that exact same contraption as you have, Have ben using it outside, but frankly it is not very handy there, so maybe I bring it in and use it as additional greenhouse. Have been using a small electric fan heater, but also a 12Volt ceramic heater. But a blowdryer is actually a good suggestion as well.

    2 replies

    Reply 1 year ago

    I tried a 12V ceramic heater as well, but I found it not to be very efficient. With the hairdryers it takes about 3 minutes to heat-up from about 16 to 20 centigrades for each enclosure.


    Reply 1 year ago

    fully agree. I started out with that... but when it got very cold it just couldnt keep up. The electric heater I had was just too powerful, but the föhn is a good idea. Will try that


    Reply 1 year ago

    Hi, thanks for that, it's fixed now.