There’s a port for a humidifier and I used a wet towel last year. Using the humidifier option this year.
Actually had quite a bit of frustration finding a “dumb” humidifier. I’m hacking a cheapo Amazon unit because I want to control it from the cabinet PCB, which will just turn it on and off as required. The cheapies I looked at all required some button pressing to turn on after turning on power
Just got the humidifier running from the switched port for it, this is the Absolute Humidity (AH) firmware revision
I can’t quite make out if you are talking to me or @Greenup, @Jasper.
If you are talking to me, I’ve already tried it, used it last season on several pounds of outdoor. You’ve seen them but posts 89-90 show some of it to other readers. I got stellar results using my constant-VPD method in the mid-60s both RH and temperature. Coincidentally, that’s very close to what the Cannatrol runs - the VPD there is ~0.74kPa (what I was controlling) and the DP is 53. I’m going to give it a run using the absolute humidity for two reasons:
Baseline the behavior of the Cannatrol method and compare to my independently-derived method (which was to control moisture removal RATE)
Controlling absolute humidity is critical to regulating the END-STATE moisture content. It was almost an accident I got perfect cured moisture levels last year, I was focused on making dry take longer than 10 days. I want to try cobbing my NLD buds this season, which requires a partial dry. So I’ll set the AH to correspond to that water activity level I want in my buds during the curing process.
And I’ll absolutely keep this thread updated on what I find. Maybe it sucks, I’ll say that if it happens. In terms of cost, the controller I designed seems to cost about $150 to make but it’s less powerful than what some other folks are doing. It cost me negligible cash because I have these components lying around so I really just purchased the PCBs. The advantage is the flexibility - I can program whatever algorithm I want to run. So can anybody else. Hindsight, maybe a RPi and small touchscreen would have been easier as things get more sophisticated. The rest is up to the builder. I don’t think there’s much novel about the controls I’m just the only person that actually did/does it and posts it for anyone to see/copy/criticize/offer input. I’ve probably got a few hundred bucks into mine but it really wasn’t about saving money. I would have bought a cannatrol last year if they had twice the capacity and could serve in an extreme environment (like my shed). It’s a fun project, and I love trying to improve things. I hope to get the best possible results. I frankly don’t care about Cannatrol, it’s not a competition or anything. I’m glad people are happy with their results regardless of how they get them. I’m happy for Cannatrol to have found a productive niche in the cannabis scene to carve out a living. I’m not going to get spooled into the arguments about techniques, wine fridges etc. because it just isn’t productive or useful. There ARE several folks here actively building and using systems very much like this but they don’t frequently appear in the discussions about them likely for the same reasons. It’s all experimental.
What this all boils down to, is the same as growing your own herb. It smokes better if you grow it yourself, I think the same thing is true of the technology used to process it after harvest. Especially if you wind up with a scientifically optimized solution. Same as growing again.
Thanks for the input!
I think @firehead was working on something a while back using different hardware. So he might be another they were referring to.
I like the using absolute humidity as the target.
I would consider a cabinet with a top mounted evap. Gravity feed should allow to pull consistent, homogeneous temps as long the shelving conducts and has some holes. Doors are mostly closed on these things and really not a lot of load.
Not sure a conversion on a single door fridge, wine/beer cooler might not save a ton of work if could find one used.
I dry in a tent or cabinet with the AC Infinity controller using just VPD or RH for now.
I like the work.
The system I’m currently running, is:
So about $45 to make a fully automated environment controller
Very cool. Can you share anymore about the software you use/wrote? Anything about how you hook them up? A guide for those wanting to build something similar?
Heck yes!
If you are already fairly tech savvy, and familiar with raspberry pi’s:
The app code and description is here:
But the best way to install it is with this installer script:
Requirements: Minimum
Install:
After raspberry pi has been installed with a fresh OS, and connected to your Wi-Fi…
SSH to the raspberry as user “pi” (on a Mac, use Terminal. On Linux, use any Xterm/terminal app. On Windows, downoad and use MobaXterm app)
ssh pi@raspberrypi.local (or ssh pi@ip-address)
4 run the install script:
[pi@raspberrypi] bash ./install.bash
Install may take up to 2 hours to complete all compiling
After install:
Point a web browser to the address of the raspberry pi (or, https://raspberrypi.local will work on most browsers)
Login to web page with “admin/potnanny!”
Click “+” on main page to create a new “room” (name it like “my grow tent”, or whatever)
Go to settings → devices → scan new devices
After your Bluetooth devices are found, go to settings → devices.
Click on a device and assign it to the room
After a device is assigned to a room, the software will begin polling info from it every 10 minutes.
I’m working on some better, instructional YouTube videos for how to get this set up… but for now, the text instructions are the best I’ve got… 
Also, please be aware… this is BETA software. It works great, is is very reliable and stable. But I am still making tons of changes to it every week and lots of things are subject to change
Thank you for taking the time to write this up. Even though I am already building the @FieldEffect project I am eager to check out your code and give it a try. I have almost no raspberry pi experience but what a great project to get into it.
I love how willing everyone is to share their work! Some people I think might like this thread @Rhino_buddy @mstopps @davjoszie - check out this if you are overwhelmed by the soldering on the project, a $45 solution that might work for you.
Dang, that’s just cheap enough for me to consider for a budget run. $45 for a controlled environment? Nice work.
Thanks for sharing this @Greenup ! Definitely going to check this out!
Getting ready for the second season. Cleaned up the wiring for switched AC (low current stuff like the water pump and humidifier) as well as unswitched outlets to plug in the controller itself.
Running controlled AH with a new screen showing detailed measurements:
Been running in the office for a few days making sure I’m happy with it before it goes back to the shed. New air filters are due to arrive later this week.
First harvest of the year in a few weeks getting everything upgraded 
I use an atomizer style, and diy a humidifier. They can be relatively cheap, especially if you only need a little added humidity, and easy to “scale”, in that they come in 1 or more “discs” options. Can be pricey in the larger units - not necessary for a project like this cabinet, I think. I use a single disc unit in a dry/cure room that’s about 4x6x6, especially in the winter.
Funny you should mention that, I wound up just buying a $10 disk and used the blower/carcass of the “smart” humidifier 
I’ll throw some pics of the atrocity sometime. Frustrating that it won’t run with pure distilled and I have to add a splash of tap water to get it to run.
Hi Greenup, I ordered those parts, I’m trying to help a friend progress to a better dry/cure/storage situation. I just found this site, very interesting with knowledgeable folks sharing the fun. Thanks for the link. And thanks to Field Effect.
The cabinet is in use once again, with some updates!
Just harvested my Indiana Bubblegum and a bit of 907 Blue Genes. I don’t measure weights hardly at all anymore but there’s a good amount in there. Several pounds wet for sure, each tray feels like a wet pound but I have no real idea.
Here’s the whole setup with ghetto tent and craigslist AC (my shed still reaches almost 100F during the afternoon, this is just to take the edge off that for the cabinet to stabilize a bit better).
I wrestled mentally with what I was going to set this thing up to do. I settled on controlling absolute humidity, rather than dew point. First of all, I believe that’s what our objective actually is. Second of all, the Cannatrol guy seems like a dick and his wife mentioned “law suit” when I met them at the CannaCon and explained I had been controlling the VPD specifically rather than RH or DP and was inquiring as to how you regulate end-state moisture when doing that. I had proposed something like a 2-step process, slow dry at fixed VPD and then a cure cycle regulating RH at a more suitable water activity level. I think it was maybe a little too close to reality.
The downside to my VPD control (which I probably typed about quite a bit last year) was that the water activity level could drift significantly as temperature fluctuated but the VPD, as intended, would stay constant. VPD sets the rate of water removal, which is exactly what I wanted, with the somewhat less-understood fact that my end-point moisture rate was variant rather than fixed.
What we want is actually both - end state water content AND removal rate. Which, regardless of technique, requires both temp and water content to be regulated.
Here’s a table of sample values and what I’m trying this dry:
The Cannatrol default is 68F temperature and 54F dewpoint, equating to about 61% RH. I’m going to try keeping the end state moisture level consistent with that, at a lower temperature and water content to LENGTHEN the dry time. So I’m going to target 63F-65F at a AH of 9.2g/cubic meter or 50.3F dewpoint. It’s kinda in the middle of what I did last season at metrics equating to 60/60 for 14 days and what the Cannatrol manufacturer recommends at essentially 68/61 for 8 days. It stands to reason that my buds should be pretty awesome in 11 days with an intermediate VPD.
Here we go
I also want to make a little note down here that the more I learn about this stuff, the less impactful I think all this nuance is. That’s not going to stop me trying to optimize. Just throwing it out there.
You scared the crap out of them… 
VPD is what the plant experiences, DP is just something to be avoided.
Cheers
G
Well, a week ago I started my dry using AH control.
I also got a temp/RH logger. The downside to starting dry in the shed is that the temp extremes are pretty wild but averaging ~60F right now. If I just circulate water with the cooler continuously, I get an internal temperature that fluctuates between 58-68F. No ice. It fluctuates a lot because the cabinet is almost continuously exchanging air to keep the moisture level at the setpoint. We’re at a point where I’m just “curing” and the exhaust or humidifier rarely run and it’s just a sealed box. That makes temp regulation much easier because I’m not effectively heating/cooling tons of exhaust air with my water reservoir.
Cabinet temp this week:
Shed temp:
RH this week:
You can see the high peaks where I was adding new flower but towards the right we’re under regulation.
Anyway, despite the AH regulation working properly (I kept my setpoint after the additions of wet flower calmed down) the RH is all over the place. This is somewhat intentional, it’s not what I’m trying to regulate. But at the end of the dry, I want a fixed water activity level, or RH. So yesterday I switched back to fixed temp/fixed RH to cure at a water activity level of 0.62.
Anyway. We’ll see how it works. I worry with my wild temp swings during initial dry, with huge amounts of exhaust operation, the AH regulation incurred periods of pretty large vapor pressure differential (high temps and low RH) that would be less than optimal. When I ran last summer I added ice everyday and kept the temperature under better control.
I think the optimal approach is probably to start with VPD regulation like I did last season for the first week, then go to fixed RH for “cure.”
Just sharing my findings in real-time. I think given my temperature swings my AH control technique should be swapped for VPD as I did last season. I added ice and will continue to do that to keep my temperature under better regulation.
Here’s a log of events to date.
My lack of temperature control is the driver behind the swings. I fixed this last summer using a ton of ice, but I really didn’t want to do that this season. Looks like I may be doing it anyway.
You can see the first few days of the cabinet struggling to keep up as I am adding fresh flower from multiple partial harvests. It stabilizes the morning of the 3rd, after my 907 harvest the night prior dries off a bit. I was concerned with the high vapor pressure differentials at the end of the day, when the cabinet was at maximum temperature with a fixed AH/dewpoint. I decided the morning of the 6th to fix this by either bounding the maximum allowed VPD or changing back to fixed RH regulation for “curing.” Anyway, I bodged up my code making these modifications and didn’t notice until a couple hours later - my humidifier had stuck on. Fortunately, this just wet my filter, so I removed the wet filter and put a new one in, fixed the code bug and we’re running that way since.
Part of me is embarassed to post this, since I expected better results and I’ve been making lots of changes (got rid of some cooling, change control mechanism). In a stable environment this would work much better than it does in my shed, most of these struggles are fighting with the external temperature changing so dramatically. But there it is.
