Automating CP Terrariums


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Hi all,

 

Long-time lurker, first-time poster. I’d like to share a guide I’ve just written: it explains how to build a low-cost terrarium controller using a Raspberry Pi 3. As you’ll see from the photos, this is based on my experience keeping a terrarium for young Nepenthes.

 

 

The system does a great job of maintaining a steady daytime temperature - I get half a degree of fluctuation around my chosen target of 28.5 degrees C, and humidity is always above 85%. The system also intelligently controls my lighting, cooling fans, and circulation fan. Finally, all data is plotted to a cloud service allowing me to monitor conditions remotely.

 

 

 

 

My terrarium is constructed from an Exo Terra - I’ve replaced the screen top with a pane of glass to retain humidity, and fitted a T5 fluorescent lighting unit to the top. The bulbs provide all the heat I need, so no separate heating pad is required. Some small PC fans are positioned to cool the lighting fixture, but these only activate once the interior temperature has reached my daytime target. An interior circulation fan runs during the day to prevent the glass steaming up. 

 

 

The night time temperatures in my flat aren’t cool enough to grow true highland species (it’s generally about 21 degrees C), so I’m instead growing tolerant intermediates and hybrids - N. sanguinea, N. maxima, N. ampullaria x ventricosa, and N. veitchii x platychila. They all seem to love it - the photos in the article are quite out-of-date, and all are pitchering profusely. I’m also trying my luck with N. spectabilis x ventricosa - I've heard that this plant might not like warm nights in the long run, but for now, it seems to be growing rapidly like the others.

 

Anyway, I hope this guide is useful to some other growers. I’m happy to answer questions if anyone’s thinking of building something similar, and I’d be keen to hear other people’s experiences with automating terrariums. 

 

 

 

Tom

 

Edited by tombennet
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Hi Tom,

 

Nice howto! Just wanted to mention, the humidity sensor MAY show a significant offset when exposed to high humidity for long periods of time. It's a feature of almost all capacitive humidity sensors and especially these cheap ones. I have expensive Sensirion sensors (DHT22 is a clone I believe) and even they have at least +/- 5%RH accuracy in high humidity + the offset of 3%RH or so after some time in high humidity. Of course in a terrarium +/- 5%RH is enough. You could have another system to check the sensor in the terrarium for offset every now and then.

 

I myself have not used Pi for my terrarium. I have a similar system, for temperature monitoring only at the moment. I am building RH meters which use the Sensirion sensors (high accuracy) and some day logging the humidity too. My main problem is the humidity controller I use. It develops a 10-15%RH offset which is a LOT. I also have a heater system which is controlled by an industrial PID controller.

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Hi pmatil.

 

I've heard stories of the humidity sensitivity of DHT sensors deteriorating in these conditions - luckily for me, it's the temperature I'm mostly interested in. When it's too hot, cooling switches on, simple as that! Humidity isn't hard to maintain in my terrarium, and realistically it can't ever get too humid for Nepenthes. I've got an internal circulation fan to help encourage air movement and prevent mould. 

 

Still, I'd be interested to hear what solution you end up using for your humidity controller. Also, what heating system are you using? I'm thinking of creating a similar terrarium for lowland plants one day (I'd like to grow an N.bicalcarata), and have been looking into heating mats to raise the temperature.

 

Thanks for the comment!

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