Quote:
Originally Posted by Orchidwizard
uff my computer hates the full sized images used in this post but the content is great.
Thanks for showing us what it takes to keep mounted Orchids happy.
One reason I suppose you don't read about terrarium growing much is because as you have described well it is a constant learning curve and perpetual adjusting and fiddling.
Your observations on air movement and humidity control have been very informative especially your visit to the mini orchid nursery. Orchids love to have air around them and have as much access to water without restricting air flow. I grow quite a few small orchids with no air flow and this works fine too as long as there is no moss restricting air - like you pointed out live moss competes too much with Orchids - it is a shame you don't know what slow growing variety you use that works better, the substrate needs to be as loose as possible to allow air flow to the roots (vitally important with no air movement) , humidity can never go above 90% and overcrowding should be avoided.
You mention having to set up complicated fan timers and manually adjust the timings to adjust humidity but there are very cheap devices called humidity fan controllers that do exactly that, automatically, once a set humidity is reached the fan is switched on, once it reaches the set minimum it turns off again, this in conjunction with a constant low other fan would sort your manual humidity issues. It is something I have been debating to get for a while but mine copes except for me having to adjust things every season or so as the weather changes.
I already have lights, timers, heatmats, daytime temp controller,s night time temp controllers, the mistking is very expensive and adding a humidity control on top is too much for me. Maybe one day..
I like how all of the basics of your setup are quite easy and inexpensive to make, once you add all the extras it adds up of course. I have a glass terrarium but moving that is a mission and yours would be good as a second terrarium if I wanted to expand mine...
Automation is the key for me to expand further. Again it is finding the balance between providing the max watering without restricting air flow to the roots in any way, cheaply, automatically and efficiently.
A mistking is imo too expensive for a mini terrarium so I am experimenting with different methods and I would post them but I think you did the right things to wait a couple of years before showing any results and I will have to be patient and do the same.
I have got one important question I am hoping you can help me with if I ever adopt your shelf design. I can see you have a drip tray and the outside is surrounded by clear plastic but when the mist nozzles come on don't they spray out of the tray onto the plastic sheeting? To me it looks like the plastic sheeting runs outside of the humidity tray so anything caught by it would flow to the floor? Or do you have additional sheeting all around the tray (hard to see) that keeps water inside the tray without it spraying out of the setup?
Also, I am curious about controlling the speed of my fans, I just have different powered fans that I use but I have wanted to tinker with them, what fan speed controller do you use to control the speed of computer fans? Thx |
Yeah automation has been key for me with the minis. They grow a bit slow, and one mistake can set them back months. The chances of me messing something up in the time it takes them to acclimate, root, grow, and bloom are just too high. If you get sick, have to go out of town, get busy with work, it's not realistic for most people to provide perfect consistency for a year.
On my big tank, the pvc frame is wrapped tightly in plastic. That whole thing sits INSIDE the tray. The front of the terrarium is just a plastic flap that can be lifted up, or tucked into the front of the tray when it is down. Any water that sprays onto the sides (which happens each time I mist) just runs down the sides into the tray. I'm sorry I don't have any pictures of this specifically, but look at the second picture in the very first post.
For fan speed control, I couldn't find anything that would change the speed through the day, so I built my own. I have used
this speed controller before, it is ok. You just set the speed and leave it. Works for adjusting a single fan but not useful for simulating weather, daily cycle, or humidity control.
It looks like you and I have slightly different humidity control issues. I'm trying to run my circulation fan more, and need to keep humidity up. I've never had problems with humidity being too high, only with the roots being too wet (with liquid water trapped in sphagnum). I'm trying to work out my airflow and moisture first, and then I want to start mounting without sphagnum.
---------- Post added at 06:38 PM ---------- Previous post was at 06:33 PM ----------
Quote:
Originally Posted by DirtyCoconuts
one other thing to throw out there is that this tank is a super terrarium with many zones and the ability to have several RANGES of plants....that is hard.
making one small niche is not as hard. I have made tanks (for reptiles, not for orchids) with really narrow climate needs at that is actually a lot easier bc you have directions.
kind of like cooking vs baking....hyper specific vs more improvisational.
one of the things that is so incredible about this tank. but not all tanks need to be so ambitious
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I'm not sure if this is what I'm doing. As I've added more circulation, I feel like my conditions have become MORE uniform. The constant airflow really helps equalize temperature and humidity through the tank. I think most of my plants are intermediate, and prefer medium airflow and regular watering. I haven't deliberately put cooler/wetter species toward the back or bottom.
Light however, varies tremendously from the top of the tank to the bottom. I really only have a few plants that like to be at the top of the tank. Most prefer the mid level, and divisions or low light plants might do a bit better at the very bottom. The few dendrobium and bulbos I have seem to like a lot of light.
---------- Post added at 07:02 PM ---------- Previous post was at 06:38 PM ----------
Quote:
Originally Posted by MJG
This is how I've planned my terrarium. I have the parts. I'm just waiting for the new terrarium to arrive. There's one piece of this I'm worried about. Where do you place the humidity probe to get a proper reading? I foresee mine getting rained on every time the sprinklers come on, which will trigger the fan. Mine's also a 36" high tank. It's bound to be more humid at the bottom than the top.
I can live with the probe being halfway down the tank for an average tank humidity reading. But how do you place the probe so that it's measuring the tank's humidity -- as opposed to how wet the probe is?
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I learned a lot about this when I started building my humidity sensor. It's actually amazing how much humidity varies through the tank. Relative humidity also varies a LOT with temperature, even if the air has the same amount of water evaporated in it. This can make the top of the tank near the lights even dryer than you might expect, and is another great reason to use LEDs. You'll even see higher humidity close to the plants if there is low airflow, just from transpiration off the leaves.
This calculator is fun to play with:
Dew Point Calculator
For example, you can see that 80% humidity at 70 degress (F), is only 54% humidity at 80 degrees.
I wasn't able to get a stable, accurate humidity measurement until after I got the circulation fan running all the time on the little test tank.
Unfortunately most humidity sensors have serious problems in terrarium conditions. They aren't water proof, they break or permanently read incorrect humidity if you get them wet. They have poorer accuracy in very wet or dry conditions, which usually means <20% or >80%. And their readings drift over time if they spend more than a few days in these extremes. I recently tested one that accumulated 5% error in just one month inside a terrarium, I gave up on it rather than continuing the test.
This is fine if you are controlling a bathroom vent fan or something, it just needs to turn on when the air is "wet", and turn off when it is "not wet". If you are trying to accurately maintain or measure humidity, I don't really think this is adequate. Especially for growing orchids when what we really care about is the 70-100% range. We are talking about how the air dries out the plant and the mount, so if the real humidity is 85% and the sensor says 90%, the air is
50% dryer than the sensor thinks (15%/10%)! The plants see some variation naturally, so this isn't necessarily bad. Just know that the readings from most humidity sensors can be very inaccurate in our conditions.
---------- Post added at 08:05 PM ---------- Previous post was at 07:02 PM ----------
I guess I should post about the humidity sensor now, since we are talking about it. I have used a bunch of cheap humidity sensors in terrariums, and they all broke within a few weeks. I did a bunch of research into humidity sensors before I started this, so I'm going to dump some of it here.
As far as I've been able to find, there are really only two types of humidity sensor:
-Capacitive, these sensors are tiny integrated circuits that measure how the capacitance of a polymer membrane changes as it absorbs water from the air. This is what pretty much all affordable humidity sensors including handheld meters, the govee, and other terrarium products are based on. Unfortunately these are not waterproof, if water gets onto the sensing element it can permanently damage the sensor. Obviously this is bad if we are spraying mist around. This type of sensor is also not able to withstand prolonged exposure to humidities above about 80%. In a high humidity environment the sensor output will drift up, causing the sensor to report a humidity that is erroneously high.
-Chilled Mirror Hygrometer (CMH), this is a precision optical instrument that uses a reflectance sensor and chiller to cool a gold plated copper mirror until condensation forms, and then measure the mirror temperature. The temperature at which condensation begins to form is the dew point of the air. These can be very accurate and robust, but typically cost $5k-10k (my hobby budget would never financially recover from this).
Way more than you ever wanted to know about humidity measurent:
Hygrometer - Wikipedia
I am trying to address the shortcomings of the capacitive sensor, so it can be used in terrarium conditions. If that does not work, I may try to build a cheap CMH.
Fortunately the first waterproofing step is provided by the manufacturer. A couple of manufacturers have started to offer sensors with polymer membranes over the sensing element. This blocks liquid water and dust, but allows water vapor to diffuse through and reach the sensing element.
This is an example of a sensor with no membrane cover.
You can see how water droplets from a mister could drift right onto the sensing element in the middle.
I'm using this tiny part:
The actual sensor is the little square near my finger, the rest is just circuit board and connector. That white square over the sensor is the polymer membrane. This part is a +/-1.5% humidity sensor, and +/-0.1 degree C temperature sensor in one package. Having both temperature and relative humidity is critical for calculating other air parameters like absolute humidity and VPD.
VPD is super interesting, this is one of the best sources I've found about it:
The Ultimate Vapor Pressure Deficit (VPD) Guide - Pulse Labs
After getting a sensor with a protected sensing element, the next step was to protect the electronics, and keep liquid water off the membrane. If you get water on the membrane it won't break the sensor permanently, but it will just read 100% humidity since it is literally under water.
I used a cable gland, a 1/2" pvc coupler, and a plastic vent plug filter.
My hope was that this would be adequate for protecting the sensor, and allow only water vapor to reach the sensor. This turned out not to work too well. It was ok for a few weeks, but when I finally did get it wet, it just trapped water in the housing. The sensor was measuring an erroneously high humidity until I dryed it out. The actual sensor was working fine, but since there was water inside the housing, the humidity at the sensor was higher than the humidity in the rest of the tank.
I've given up on the vent plug, and no longer use it. I just let the fan keep the sensor supplied with fresh air for accurate measurements of the terrarium air. The sensor is pulled back into the housing by about 1", and the opening points down, so water doesn't really get up inside.
This is the version that accumulated 5% error over the first month of test (it reports humidities that are 5% higher than sensors it used to match perfectly, that were never exposed to terrarium conditions). After determining that it was no longer accurate I gave up on this version and started a second one.
The next version needed to do something to ensure the sensor would never experience >80% humidity, so it wouldn't drift over time. The only way I could think of to do this was to heat the air at the sensor slightly to drop the relative humidity right at the sensor. Because the humidity sensor has a temperature sensor built in, I can still accurately calculate the absolute humidity of the heated air. Then I needed a second (unheated) air temperature sensor to convert back to the relative humidity of the terrarium air. It sounds like a lot of steps, but it actually works great! This resource goes into pretty good detail about how these measurements and conversions can work:
https://www.silabs.com/documents/pub...otes/AN607.pdf
This next prototype is a little bit hacky, it just has the air temperature sensor strapped to the side and the heater is inside right at the sensing element.
This version has been in the tank, at >85% relative humidity at all times, and seems to still be completely within the specified accuracy. I take it out of the tank to compare to ambient sensor data about once a week. I have really high hopes for this one.
The dashboard is currently showing data from this sensor:
https://io.adafruit.com/jdamelio/das...ity?kiosk=true
On the humidity plots, orange is the humidity of the heated sensor, red is the target humidity calculated from a VPD of 0.3kPa and the air temperature, and green is the actual terrarium air relative humidity.
On the temperature plots, red is the heated sensor temperature, green is the terrarium air temperature, and blue is just temperature of the air outside the terrarium.
There are bunch of really cool little details on these plots. For example you can see a tiny drop in temperature each time the mister goes off. This is from the evaporation of the mist into the air. You can also see the humidity decreasing slightly whenever the fan speed is higher. And you can see the humidity get bumped up by the mister each time it falls to the target humidity! You can also see the humidity fall when the lights turn on, and rise when they go off, just from the 1 degree C change in air temperature.
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