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By Supercazzola
Posts:  785
Joined:  Sun Nov 22, 2020 1:57 am
First off, I have to thank Taylor Davis ( @incectivorouscircus on instagram) for her help and guidance. The integration into Home Assistant and some other aspects are my own dorky contributions, but she really helped me along with answers to basic questions.

My motivation is that I live in Florida, where the heat (even inside an air conditioned house might not allow for the temperature swings that highland Nepenthes need). Also, I am lazy, and was tired of bringing lots of ice packs out from the freezer each sunset to put in a thermal cooler for my Jamban, and then remembering each morning to get the ice packs out and back into the freezer.

List of things I used:
  • a 7 cubic foot chest freezer. I went with this one from Walmart, and I bought it new because I wanted something with a warranty ... hbdg=L1100 ~ $200 USD
  • a piece of "egg crate" similar to this one ... /202025149 ~ $18 USD
  • some 1" PVC and couplers (used to raise the egg crate off of the floor of the freezer) - ~ $15 USD
  • a yescom 225 LED light - I had a spare red/blue one, but probably would have preferred a white one ~ $25 USD
  • some DC fans to keep air circulating (in the enclosed environment, this is very important). I chose these, only because they came with a AC to DC adapter, and some sore of variable speed control. ... UTF8&psc=1
  • some sort of thermostat controller - You would want one with a day and night temperature, for example one like this ... UTF8&psc=1 ~ $65 USD, although in my design, I used some different smart outlets - see section on automation for more info
  • a piece of 1/4" or thicker clear acrylic / plexiglass to be used as the new lid. In my case, this measured about 21 1/4" x 32 1/8" with fillet (rounded) corners ~ $70 USD
  • some weatherstripping to go between the top surface of the chest freezer, and the piece of plexiglass ~ $10 USD.
First step was to remove the lid from the chest freezer. In my case, there were some plastic covers over the hinges that I removed, and then it was a matter of loosening some screws, and then the lid was off.

Next, I measured and made the PVC stand to raise the bottom of the egg crate. I also measured and cut the egg crate to size using some gloves and a pair of diagonal cutters. I like using egg crate and having it raised because it gives me room for (one of) the fans, provides a place for the water to go, and also brings the plants closer to the top / light source. I went with a design like this, but I am sure there are many different ways
IMG_4774.JPG (45.15 KiB) Viewed 900 times
I used some tie wraps to hold the egg crate to the PVC. Here it is, looking down into the chest freezer.
IMG_4775.JPG (2.45 MiB) Viewed 900 times

Next, I laid the weather stripping around the top of the freezer, so that it made a nice seal between the top of the freezer and the plexiglass. Placed the light on the top of the plexiglass and plugged everything in for a test. I put one of the fans under the egg crate, blowing one way, and another above blowing the other way, like this:
IMG_4776.JPG (767.94 KiB) Viewed 900 times
At this point you could use a controller like I listed above to set the day and night temperature, plug the freezer into the controller, remember to keep the controller's probe inside the freezer, and be done. But I chose to integrate it into my existing Home Assistant instance. See my previous post on my grow tent automation post370483.html#p370483 for more background.

IMG_4773.jpeg (2.99 MiB) Viewed 900 times

Read on for part two, the automation of this chest freezer.
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By Supercazzola
Posts:  785
Joined:  Sun Nov 22, 2020 1:57 am
So, I know of a few stories where folks had thing go wrong and their highland species turned into plant-sickles being exposed to sub freezing temperatures. I wanted to design a two fault tolerant system to avoid that.

My basic idea was this: Have a master switch that would cut power off to the whole system. This switch would in turn provide power to another switch, which was thermostatically controlled. This second switch was what the chest freezer was hooked into. Temperature probes would read the temperature, and then would allow power to the freezer until it reached the desired temperature, then cut power until a certain threshold was reached (as the unit lost cold through the plexiglass top). Then it would apply power again, and the freezer would cool down until again the desired temperature was reached....

So let me outline what I did.

I used a standard smart switch (Sonoff S31) ... UTF8&psc=1 as the main switch to be able to cut power to the entire system. I loaded tasmota firmware on it, to help me with integrating it with Home Assistant. OK so now I have a master ON/OFF switch that can be commanded over my wifi to turn on or off.

Next, I chose a smart switch also has capability for a temperature and humidity sensor. Sonoff makes a few, but I chose Sonoff TH16 WiFi Smart Switch with the DS18B20 probe. ... UTF8&psc=1 . I loaded Tasmota on this also and got it working with Home Assistant.

It was at this point that I realised I desired another smart switch to help me turn on and off the grow light. I could have used another S31, but had a spare Sonoff TH10 Smart Switch which had the bonus of another temperature sensor (this one based on the SI7021 probe). I loaded Tasmota on it and got it working with Home Assistant.

Confused? Don't be... At this point, I have three smart switches, two temperature probes, and one humidity probe.

OK, so here is where the magic of Home Assistant comes in.
  • It knows where I am located, so it knows sunrise and sunset times each day - so you could use that to turn on and off the grow lights. You can even specify an offset, if you wanted to keep the lights on for 3 hours more than from sunrise to sunset...
  • It has a built in Generic Thermostat "integration" - so I provide it the switch I want to control, and the sensor it should use for temperature monitoring and then the temperature I want it to keep the system at and it does the rest.
  • You can take a bunch of temperature sensors, scatter them in the freezer (even 100% wireless ones, like Zigbee based ones) and create a "mean/average temperature" sensor, and use that in case one probe went belly up.
  • And having the master power switch, if the thermostat integration failed, the monitoring of the temperature probes could turn off the master switch when the temperature got to some dangerous level (for example, if the temperature inside the chest freezer falls below 40 Degrees F for 1 minute kill power to the whole thing.
  • Home Assistant also integrates nicely with my iphone and can send notifications to the phone (or apple watch), so if the temperature was showing a trend of going below 50 degrees F, I could have it send me a notification and I could take manual action before the safeguards I have designed would kick in...
The possibilities with Home Assistant are endless. That being said, I do realize that it's not for the faint of heart - also if the Home Assistant server ever crashed or something happened to my home network, I could be in big trouble.

Hence why I also own one of the commercially available Day & Night Cooling or Heating Thermostat devices. Just in case...

But integrating this chest freezer highland chamber into Home Assistant has been fun, and I enjoyed the learning experience. And, it seems to be working really nicely so far:
Screen Shot 2021-09-20 at 4.24.49 PM.png
Screen Shot 2021-09-20 at 4.24.49 PM.png (92.11 KiB) Viewed 893 times
I have it setup like this. At Sunrise, turn on the grow light, and set the desired temperature to 75 F. At Sunset, turn off the grow lights and set desired temperature to 56 F. The internal fans are always running. If at any time the temperature goes below 48, it notifies me and then cuts power off to everything.

Feel free to ask any questions, find any flaws or provide additional suggestions to me, and I will be glad to answer.
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By Rammplins
Posts:  384
Joined:  Fri Apr 21, 2017 6:28 pm
Looks great! And the power cutoff is a great decision to avoid plant-sickles. Only problem i can see for the future is that the acrylic will probably eventually warp leaving gaps in the seal. Not a huge deal but it bugged the hell out of me when mine did that, especially after I made sure that it fit perfectly at first. As for ways to stop that from happening I have yet to come up with one other than using super thick acrylic that is dumb expensive.

You may also want to take some fine grit sandpaper to the edges of the plexiglass, if i had a quarter for everytime i cut myself on my lid I would be able to buy a nice meal at wendys.

Sent from my SM-G975U using Tapatalk
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By Nepenthes0260
Posts:  1300
Joined:  Mon Apr 30, 2018 1:59 am
Wow, what a nice setup. :shock:

I agree with Rammplins, you may want to sand down the edges on your plexiglass sheet, especially if you’re going to be opening it regularly. I have an assortment of scratches on my hands from the same thing. :lol:

You could probably expand into Heliamphora now with that nice grow area. ;)
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By Z_Y
Posts:  145
Joined:  Wed Jun 24, 2020 10:19 pm
Nice setup! I have a few suggestions:

- make sure to take into the account the failure mode where the freezer never turns on but the lights stay on. Cooking the plants is also not desirable. A kill switch for high temperatures would be a piece of mind.

- I have had wireless relays fail to switch sometimes, maybe due to a bad network connection. You can try to mitigate it a bit by sending multiple On/Off signals over a few hours. For example, if you want to turn something on at 8am, set an On signal for 8, 9, and 10 am.

- If you are good with some programming, try to add in a heartbeat from server to the kill switch if you can. That way if the server fails the kill switch will shut everything down by itself.

- Make sure to test for brownout or power flicker situations, such that all the sensors can reconnect themselves correctly if there is a momentary power failure.
User avatar
By Supercazzola
Posts:  785
Joined:  Sun Nov 22, 2020 1:57 am
All good comments.
I’ll add one for the high temperature.
I know the weakness of the system is the reliance on the home assistant server, which itself relies on my home network. Not the Internet, though. All I have to do is keep the LAN up. Since I have the equipment on UPS, I feel ok for short power outages. The circuits are also on a whole home generator, so the UPS really just has to hold over until the power transfer happens.
One of the reasons I like Home Assistant over something like Amazon Alexa or Google or Apple Home is that everything stays local. It’s not going to some server in China / in the cloud.
Every system has its own inherent risks. once I implement the suggestions everyone shared, I think I’m even more happy with the risk posture.
Thanks again for the observations.
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By Supercazzola
Posts:  785
Joined:  Sun Nov 22, 2020 1:57 am
Have had a few hiccups already. Once, where the unit did what I told it to do, which was turn off if the temperature got too cold. This happened in the evening, after sunset.
When sunrise happened, the command to turn the compressor was executed, but my power for the circuit that feeds it was still cut off due to the "emergency" power down when it got too cold.
So the temperature in it rose, until it hit the low 90s, which is when it sent me another notification and I figured out what happened and manually commanded it.
I've corrected my actions at sunrise to include turning on the main power, then setting the daytime temperature, then turning on the lights.
Now to figure out what caused the temporary spike into the "cold" (48°F for 30 secs). But in all honesty, I probably should drop the trigger to something like 42 degrees for 5 mins...

See if you can spot the "events" on this chart.
Screen Shot 2021-09-24 at 4.50.09 PM.png
Screen Shot 2021-09-24 at 4.50.09 PM.png (99.79 KiB) Viewed 692 times
Also, the reason I did this project:
IMG_4803.jpeg (706.3 KiB) Viewed 692 times
User avatar
By Nepenthes0260
Posts:  1300
Joined:  Mon Apr 30, 2018 1:59 am
I think you'd be good if the trigger was dropped from 48 to 42. Actually, a lot of HL/UHL neps would probably appreciate nighttime drops near the 48-ish range! Jamban looking great, too.
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