Making an open source drying device -- help us get it right

Introduction first: I am a software engineer, and I am teaming up with an electric engineer.
We want to build a cabinet where you place your wet buds, and that it will dry them AND cure them.
The closest thing on the market at the moment is the pricey Cannatrol.
Our idea is to make something like the CoolCure: you get an existing sealed cabinet, and then you make holes in it and place the components (the vent, the peltier cooling element, etc) in the holes. We will release all circuits, wiring, and 3D files to print the thing yourself.

We need GOOD ideas, GOOD hints, and help. The result will only be good if we get good help. I think the Cannatrol only has a Peltier cooling system. So, I am very confused in that how they manage to target humidity and temperature at the same time. I also don’t want to create a clone of an existing product, but something BETTER.

Anyone here who can help with knowledge, ideas, hints, dos and donts?


Reply to myself: awesome explanation of what Cannatrol does: Cannatrol cool cure? Its a cigar fridge! - #6 by dbrn32

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When you’re reducing temperature, humidity also goes down with temperature, until you reach dew point, then condensation happens.
When condensation occurs, moisture is removed from the air, reducing humidity.

A refrigerator is similar to the cannatrol, and members have dried inside their fridges for better temperature and humidity control.


OK but as far as I know the peltier cooler will BOTH dehumidify AND make cold at the same time. You can’t have one and not the other. So, how does it target a higher target humidity with a COOLER target temperature?


What an interesting project, I too think its gross that the cannatrol is so much for a glorified wine fridge. A buddy and I have been working on a similar device for drying hash.


Operate the unit at a specified temperature, and the numbers will align. Which is different than operating until all moisture (or most) is removed, and temps are reduced further.

As a Cannatrol owner; if you want better, at the very least go bigger!


What is in this besides the cooling device?

I’m not sure on the rh. Last i seen of a cannatrol was on display at hydro shop several years ago. I looked at it for a couple minutes and thought the same, this is a thermoelectric beverage cooler.

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I’m trying to figure that out now, but I keep coming back to wine fridge and what do I do with the other 2/3 of my harvest.

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Not having used one, I’m not sure. I suspect that a few days in one of these would put you down a good start and if you staggered your harvest by a third at a time you could cycle through it. But I agree that a single unit not going take a huge harvest.

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After about an hour of looking through marketing material and reviews I still see a high end wine fridge with very nice controls. Still not sure that justifies the price though. Back on topic. @tm1 I made a closet out of garage door panels with a window A/C unit, humidifier, heater, and a bunch of clip fans to circulate air. I keep it 64-67 degrees and 50%-55% RH. This seems to produce similar results in a similar time frame to what the cannatrol advertises. I believe if you had better controls than the plug n play inkbird units you could get tighter control and probably replicate it exactly. Hope that helps get some ideas flowing.


Something escapes me… The Cannatrol cabinet will:

  1. Dry with 68F (temperature) and /54F (dew point). Relative Humidity: 61%**. Water Vapor Pressure : 1,424 Pa

  2. Cure with 68F (temperature) and 52F (dew point). Relative Humidity: 56.60%. Water Vapor Pressure : 1,324 Pa

  3. Store with 68F (temperature) and 54F (dew point). Again Relative Humidity: 61%**. Water Vapor Pressure : 1,424 Pa

So… if I build something that will keep those parameters stable in a cabinet, with a dehumidifier and a peltier cooler/warming element, that should be it… right?

But then again, is “jarring” the same as this?

  1. Cure with 68F (temperature) and 52F (dew point). Relative Humidity: 56.60%. Water Vapor Pressure : 1,324 Pa

Does it really “cure it”, without placing the product in a jar?


I haven’t seen you mention, they use a container with a wet sponge to help keep the humidity up. Which is one reason why I won’t consider them. All that money and I have to monitor a sponge… really.


For my system, my idea is that the water I collect from the flower, I make available in a small tray in the cabinet. When it collects too much water, the excess water goes into the overflow and gets put in a smaller outside tray/wherever. This makes the sponge redundant.

Using a Pelter cooling system is a great idea there, because the compressor of a fridge will create huge spikes in VPD,


Add a heating element to the collection tray, trigger with a humidity sensor.

The available water will diminish as the dry / cure progresses, whats the plan?

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I could easily easily have a small reservoir of water that will make sure water in the tray is always level.


Elevated reservoir with float valve, I could see it. But if doing that probably just evacuate the flower water, no need to collect.

How about the collection tray have the majority of the capacity external, with a baffle to help temp stabilization internally. Heating element could still maintain humidity. Then would just be a matter of testing if the amount of water in the flowers is enough to carry through the time needed. Probably would be.

May not even need a heating element if the internal surface area is sized appropriately. Hard to regulate that way though.

Just thinking out loud. (years of brainstorming sessions)

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Interesting ideas. The main point is to keep everything really simple.


Write up some protocols and start testing. lol

This is the path I went down, all came down to the sponge and options. I don’t have the time or inclination to hammer it out, so I went freeze drier.

As far as simplicity, a slide which covers the surface area of the collected water, externally controlled, manually. Adjust the surface area depending on humidity need.

A little more complicated would be a DC muffin fan with a potentiometer blowing over the collection pan, raise and lower evaporation rates.

Evap Rates

Configured correctly an existing fan could perhaps be utilized and the slide regulate. Choke / throttle cable would be simple.