Some of our houseplants benefit from a daily misting. Misting gives a Boston Fern higher humidity, while making life difficult for spider mites that thrive on our palms when the air is dry.
I’ve had fun in the past few weeks developing an automated misting system that can run on a schedule, or can be manually operated over the Internet.
Along the way, I’ve incorporated features to prevent water damage to our home if the system malfunctions, or damage to our health if bacteria, such as Legionella, develop in the water delivery system.
When we travel, the plants get misted manually every two weeks. This is just not enough. A daily misting by the automated system will keep the plants happy, even if we’re gone for a couple months.
The System
The system is divided into the Wet Side and the Dry Side.
Wet Side
The devices on the Wet Side are housed in a 70-liter disaster pan that can be pulled out from a shelf, as shown in the above photograph. The disaster pan is normally dry, but would contain a leak, should one of the dozens of connections fail.
From left to right:
- Manifold. Distributes water to five watering zones and the misting zone.
- Ultraviolet Sanitizer. Sterilizes water used for misting.
- Misting Pump.
- Misting Zone Solenoid Valve. The small device with two red electrical connectors.
All electrics are 24 volts.
Dry Side
A grey, waterproof project box, to the right of the disaster pan, contains electronics and 120 volt power supplies. It will not, normally, get wet.
Misting Nozzles
After some experimentation I opted for misting nozzles that produce a coarse mist, more like a fine spray. Any dampness on the tile floor from overspray is gone within 30 minutes of a misting.
I decided not to use nozzles that produce a finer mist, as they are more likely to become blocked by impurities in the water.
Water
The water pressure was not sufficient to drive the misting nozzles. Drops would slowly form on the nozzles, then fall vertically, forming a pool beneath. After some interesting research, where I learned about aeroponics, I opted for a booster pump.
Aeroponics is the process of growing plants in an air or mist environment without the use of soil or an aggregate medium.
Wikipedia.
The booster pump produces 100 pounds per square inch pressure, about double the typical residential water pressure.
As I prototyped the misting system, I was often happily distracted by tangential subjects. I found NASA articles evaluating aeroponics for growing food in space. I learned about dangerous bacteria, such as Legionella, and how they can be transmitted to our lungs via a fine mist. I found local health department requirements for the proper maintenance of supermarket produce misting systems.
After considering chemicals, such as highly diluted bleach, we opted for an ultraviolet sanitizer, the type installed in some homes to sanitize well water.
Control
Most of the electronics are in a waterproof project box. There are no visible physical controls; all user interaction is via the Internet.
If the Internet goes down during a misting or watering session, the system has sufficient autonomy for the session to complete normally. Currently, I restrict the spray duration to six seconds, which seems sufficient.
Now, we just need to go on a long trip to give the misting system a good workout.
Hello Tom,
I just found your work about aromatic misting system which I found it sweetly integrated and complex! I teach plant sciences to high school students and we have aeroponic systems. I want to include automation and grow systems development as part of our curriculum. I am not that knowledgeable in using the automation technology but I’m have installed cheap relays at home to automate lights using a raspberry pi with the hoobs system. I’m very interested in learning about how to put your system together, do you have a list of the main parts you are using available to share? What app are you using? Thanks and keep the great work.
Hello Luis,
Apologies for not responding sooner: I’ve just noticed your kind comment. Cheap relays and raspberry pi are great options.
I’ve been using a variety of systems:
Arduino computers, coupled with the Blynk app. Examples include: ultrasonic measurement of water in tank; weight of plant tray (to monitor watering and evaporation).
Wirelesstag sensors (https://wirelesstag.net/) for measuring moisture and light.
For most functions, though, I’ve been using a Spruce controller. (Yes, I know that’s lazy!) https://spruceirrigation.com/ There’s about a dozen watering zones (I’ve been using regular drip irrigation parts), plus the misting zone. Spruce comes with its own app, and is autonomous: if I’m traveling for a few weeks, and the Internet goes down, it happily keeps operating. The wireless moisture sensors, work really well.
For the misting, I used a high pressure pump:
https://www.amazon.com/gp/product/B003ZJMSEY/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
This has worked flawlessly. The system also has a UV sterilizer (to prevent harmful bacteria reaching our lungs).
In order to keep misting down to just a few seconds (the minimum time Spruce will allow is 1 minute–too long for this purpose), I use the following timer relay: https://www.amazon.com/gp/product/B07B91KRZX/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
I’ve had a lot of luck with these mister nozzles: https://www.amazon.com/Adjustable-Atomization-Capillary-Irrigation-Sprinklers/dp/B01CWVLVB6/ref=pd_rhf_ee_s_rp_c_3_3?pd_rd_w=9v4mA&pf_rd_p=26d392db-8b78-4d00-b33d-2981cba34f91&pf_rd_r=ZQJ3KZFS9Z4K2HKEJMZC&pd_rd_r=1a1f278c-4e0a-401c-b9c8-b460eb5d8bad&pd_rd_wg=pxkTW&pd_rd_i=B01CWVLVB6&psc=1
The mist is fine enough to keep the plants moist, but not so fine that they block easily. There’s seven misters, and I’ve only had to change out two of the misters in the past year. (I’ve had bad experiences with finer nozzles.)
I’m sure I’m missing parts you might be interested in. Please feel free to ask more questions. Good luck with your students as you explore aeroponic systems. I wish they had classes like your’s when I was a kid.
Tom