An Artificial Sun for Miniature Terrariums

The wavelength of light can have a dramatic effect on flora and fauna. Animals, including people, produce vitamin D, which helps with the absorption of nutrients, when exposed to UV-B rays in sunlight. But if the ozone layer didn't protect us from it, UV-C rays would kill us — along with pretty much all other living things. Plants respond better to some wavelengths than others, so controlling the light they receive can do a lot to improve their growth. With that in mind, James Reed designed this artificial sun for miniature terrariums.

Reed's artificial sun is ideal for small plant terrariums, but one could expand the concept for larger terrariums. It isn't great for terrariums containing animals, like turtles, that require regulated heat. The LEDs used here won't output much heat at all and there isn't any hardware to control temperature within the terrarium. But because you can control the color (the wavelength) of the light, you can experiment with what works best for your plants. You can also set schedules to simulate the sunrise, midday, and sunset. Such schedules are necessary for stimulating plant growth, as you can "trick" the plants into responding like they would during a particular season in nature.

The hardware required for this project is affordable. It consists of an Adafruit QT Py RP2040 (though any CircuitPython-compatible development board would work), an Adafruit PCF8523 real-time clock (RTC) module, an Adafruit NeoPixel 24 x 5050 LED ring, and a power supply. You'll need something to protect the development board and can use either a generic project box or 3D-print an enclosure. You'll also want a capacitor and diode to protect your LEDs, as recommend by Adafruit. Those aren't a requirement, but they are helpful.

The setup is straightforward. The QT Py controls the LEDs according to the CircuitPython code created by Reed. It uses the RTC to keep track of time in order to follow the schedule. The LED ring mounts to the top of the terrarium and shines like down into it. Any terrarium of the proper size should work, but the model that Reed found resembles a geodesic dome and looks really cool. It has a handy cork board lid that makes attaching the LED ring and routing wires easy.

As you can see, the result looks awesome. It would make a very nice piece of decor and provide real benefits to the plants inside.