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

mmob · May 14, 2024

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?

mmob · May 15, 2024

I'd love your opinion on this...

Something escapes me… The Cannatrol cabinet will:

Dry with 68F (temperature) and /54F (dew point). Relative Humidity: 61%**. Water Vapor Pressure : 1,424 Pa
Cure with 68F (temperature) and 52F (dew point). Relative Humidity: 56.60%. Water Vapor Pressure : 1,324 Pa
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?

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?

1diesel1 · May 15, 2024

No, curing takes place in the jar over time.
But you can jump start the curing process with low temps and the proper humidity in the drying space, I use plastic tubs for the curing process before mason jars are used

DougV · May 15, 2024

How do the large commercial guys cure? I see walk in cure rooms, but not enough info to understand them. I have a canning room that is remarkably stable in terms of temperature and its size makes it easy to control humidity. Works great for drying. I’d love to think I could just leave them hanging. For tobacco, drying and curing are synonyms. The reasons you cure marijuana and tobacco are the same. Is the container cure thing a myth? I don’t really understand the reasons for a sealed container. I get why you need to burb to allow for outgassing, but if I don’t seal I don’t need to burp. Fluid motion is different sealed vs unsealed. In sealed you are allowing moisture to be wicked from the moist interior to the dryer exterior, in open environment that dynamic is changed. But does that matter?

There are advantages to curing in an open fashion. Reduced risk of mold/fungi. Reduced costs, as in no sealed containers. Easier, just wait longer. Potentially reduced THC loss due to reduced handling. What I don’t fully understand is how taste would be affected. For the life of me I can’t see how sealing in a jar can improve taste vs an open environment with good environmental control. Having said this, I cure in sealed containers, I just don’t want to.

For decades Cuban cigars purchased before the ban were kept in humidors and sold. They were well cured and never kept sealed. Can we do the same?

Natep · May 15, 2024

It just needs to stay at 60 degrees and 60% humidity.

PahPahCee · May 30, 2024

mmob said:
I'd love your opinion on this...

Something escapes me… The Cannatrol cabinet will:

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

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

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?

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?

Sorry, I haven’t been on in a while.

Honestly, I appreciate the inspiration the cannatrol gave us but I don’t agree with with their drying protocols.

There is a thousand ways to approach this but ideally you want to slowly draw the moisture out of the bud while maintaining a low temperature with minimal fluctuations.

I’m sure cannatrol has a better preset for optimal quality but the ones they advertise and people talk about make me groan. They sacrifice quality for a quick dry time. If you look at their patents for their large scale units they will heat the environment up past 100F to kill spores. No thank you. That is purely for passing testing.

The home unit cannatrol is a glorified 28L wine cooler with a fancy controller that regulates the parameters. The magic really is the Peltier device.

PahPahCee · May 30, 2024

DougV said:
How do the large commercial guys cure? I see walk in cure rooms, but not enough info to understand them. I have a canning room that is remarkably stable in terms of temperature and its size makes it easy to control humidity. Works great for drying. I’d love to think I could just leave them hanging. For tobacco, drying and curing are synonyms. The reasons you cure marijuana and tobacco are the same. Is the container cure thing a myth? I don’t really understand the reasons for a sealed container. I get why you need to burb to allow for outgassing, but if I don’t seal I don’t need to burp. Fluid motion is different sealed vs unsealed. In sealed you are allowing moisture to be wicked from the moist interior to the dryer exterior, in open environment that dynamic is changed. But does that matter?

There are advantages to curing in an open fashion. Reduced risk of mold/fungi. Reduced costs, as in no sealed containers. Easier, just wait longer. Potentially reduced THC loss due to reduced handling. What I don’t fully understand is how taste would be affected. For the life of me I can’t see how sealing in a jar can improve taste vs an open environment with good environmental control. Having said this, I cure in sealed containers, I just don’t want to.

For decades Cuban cigars purchased before the ban were kept in humidors and sold. They were well cured and never kept sealed. Can we do the same?

Yes, I agree. You don’t need to be in a sealed environment. However, controlling a sealed environment is a helluva lot easier than the latter.

I don’t know if you can do a fair comparison to drying techniques of other crops. Different end goals.

terpenes are volatile and when one drying parameter is out of wack you can literally smell the terpenes leaving the bud.

dazedays · May 30, 2024

I’ve been thinking a super cheap mini fridge, a temp/humidity controller, and smart phone controller.

Drill a 2” hole in the side and tape the fan, drill a 1/4” hole and drop and affix the temp/humidy sensor. Then program using the controller to power on the fan or turn on/off the fridge using the temp controller! Plus smart phone control gives you real-time temp, programming, and more!

Less then $200.

Will you send me one if you build it? lol.

dazedays · May 30, 2024

dazedays said:
I’ve been thinking a super cheap mini fridge, a temp/humidity controller, and smart phone controller.

Drill a 2” hole in the side and tape the fan, drill a 1/4” hole and drop and affix the temp/humidy sensor. Then program using the controller to power on the fan or turn on/off the fridge using the temp controller! Plus smart phone control gives you real-time temp, programming, and more!

Less then $200.

Will you send me one if you build it? lol.

View attachment 2182177 View attachment 2182178

This won’t be calculating dew points or anything but it’ll give you the 60/60 you’re looking for. And for $200 if it sucks, it was fun to build after a few bong tokes!

lampie208 · May 31, 2024

mmob said:
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?

I mined crypto and had to have good airflow and keep moisture out, so I know how to let it in as well. I used some arduinos and Pis to create certain tasks

PahPahCee · May 31, 2024

dazedays said:
I’ve been thinking a super cheap mini fridge, a temp/humidity controller, and smart phone controller.

Drill a 2” hole in the side and tape the fan, drill a 1/4” hole and drop and affix the temp/humidy sensor. Then program using the controller to power on the fan or turn on/off the fridge using the temp controller! Plus smart phone control gives you real-time temp, programming, and more!

Less then $200.

Will you send me one if you build it? lol.

View attachment 2182177 View attachment 2182178

Compressor fridges will not work. The only successful drying method with a compressor is the lotus cure method which involves paper bags to save the bud from massive RH swings when the compressor kicks on.

PahPahCee · May 31, 2024

dazedays said:
This won’t be calculating dew points or anything but it’ll give you the 60/60 you’re looking for. And for $200 if it sucks, it was fun to build after a few bong tokes!

Don’t fall for cannatrols none sense. Dew point is nothing more than a calculation of RH and temperature. You can use RH/temp or dew point to guide your dry. It will get the same results.

I built both of my fridges for under $150 with second hand stuff. Brand new off Amazon you can do it for under $250.

PahPahCee · May 31, 2024

Wine fridge (Peltier / thermoelectric) + cheap dehumidifier (also a Peltier) + a RH controller like an INKBIRD and you got yourself a manual cannatrol. If you want to take it to the next level you can write some code and automate it.

tankoamerican · Nov 12, 2025

7–9 Day Cure – 70L – 2x TECs (Cooling) – Tire Pump Purge Mini Fridge Shell Only – No Internals

Item	Qty
Used Mini Fridge (70L)	1
TEC1-12706	2
Heatsinks + 40mm Fans	2
STC-3028 (12V)	1
1x 30A 12V Relay	1
12V Tire Pump (35 L/min)	1
Perforated Trays (4x)	1
12V 16.5A PSU	1
Misc (wire, fuse, hose, silicone)
Carbon Filter + One-Way Valve	1
Condensate Tray + Hose	1
TOTAL

WIRING 2x TECs – Max 12.6A

[12V 16.5A PSU] → [20A Fuse]
│
├─► [STC-3028: Pin 1 (+), Pin 2 (-)]
│
├─► [Relay 1] → [2x TECs Parallel] → Normal Polarity
│ Trigger: OUT °C NO (Pin 8) + OUT %RH NO (Pin 9)
│
├─► [Tire Pump] → OUT %RH NO (Pin 9)
│
└─► [2x 40mm Fans] → Direct 12V

STC-3028 SETTINGS

Code	Value	Function
F2	63%	RH High → 2x TECs ON
F5	4	Burp every 4h
F6	1	Pump ON 60 sec

BUILD

Strip Mini Fridge
- Remove compressor, shelves, old TECs
- Keep insulated shell + door seal
Drill Holes
- 2x 40mm (TECs)
- 1x 3" (tire pump hose)
- 1x small (probe + wires)
Mount 2x TECs
- Cold side inside
- Heatsink + fan outside
Wire STC-3028 + Relay
- 2x TECs → Relay 1
- Tire pump → Pin 9 (NO)
Add Airflow
- Trays 4" apart
- Hose → carbon filter
Test Empty (24h)
- Target: 68°F / 60% rh

Metric	Result
Dehum Rate	20–25 pints/day
Cure Time	7–9 days (62% → 58% RH)
VPD	1.3–1.4 kPa
Power	12.6A max (safe)
Cost/Month	$11

VPD CALCULATOR

python

def vpd(f, rh):
c = (f-32)*5/9
svp = 0.6108 * math.exp(17.27*c/(c+237.3))
return round(svp * (1 - rh/100), 2)

print(vpd(68, 62)) # → 1.4 kPa

tankoamerican · Nov 12, 2025

tankoamerican said:
7–9 Day Cure – 70L – 2x TECs (Cooling) – Tire Pump Purge Mini Fridge Shell Only – No Internals

Item Qty
Used Mini Fridge (70L) 1
TEC1-12706 2
Heatsinks + 40mm Fans 2
STC-3028 (12V) 1
1x 30A 12V Relay 1
12V Tire Pump (35 L/min) 1
Perforated Trays (4x) 1
12V 16.5A PSU 1
Misc (wire, fuse, hose, silicone)
Carbon Filter + One-Way Valve 1
Condensate Tray + Hose 1
TOTAL

WIRING 2x TECs – Max 12.6A

[12V 16.5A PSU] → [20A Fuse]
│
├─► [STC-3028: Pin 1 (+), Pin 2 (-)]
│
├─► [Relay 1] → [2x TECs Parallel] → Normal Polarity
│ Trigger: OUT °C NO (Pin 8) + OUT %RH NO (Pin 9)
│
├─► [Tire Pump] → OUT %RH NO (Pin 9)
│
└─► [2x 40mm Fans] → Direct 12V

STC-3028 SETTINGS

Code Value Function
F2 63% RH High → 2x TECs ON
F5 4 Burp every 4h
F6 1 Pump ON 60 sec

BUILD

Strip Mini Fridge

Remove compressor, shelves, old TECs

Keep insulated shell + door seal

Drill Holes

2x 40mm (TECs)

1x 3" (tire pump hose)

1x small (probe + wires)

Mount 2x TECs

Cold side inside

Heatsink + fan outside

Wire STC-3028 + Relay

2x TECs → Relay 1

Tire pump → Pin 9 (NO)

Add Airflow

Trays 4" apart

Hose → carbon filter

Test Empty (24h)

Target: 68°F / 60% rh

Metric Result
Dehum Rate 20–25 pints/day
Cure Time 7–9 days (62% → 58% RH)
VPD 1.3–1.4 kPa
Power 12.6A max (safe)
Cost/Month $11

VPD CALCULATOR

python

def vpd(f, rh):
c = (f-32)*5/9
svp = 0.6108 * math.exp(17.27*c/(c+237.3))
return round(svp * (1 - rh/100), 2)

print(vpd(68, 62)) # → 1.4 kPa

very affordable

7munkee · Nov 12, 2025

I've dried in a wine fridge. IMO in keeps the flowers wetter longer than I like. It takes more than a month. Now I just hang whole plants in my basement. When they are dry, I buck the buds, leaves and all, into a tote with a very loose lid and keep them in there to cure for a month or more. I grow for me and my 2 adult sons so if they want some herb they can go to the basement and get it and trim it themselves.

Sure, it makes my house reek, but I'm rural so IDGAF.

mmob · Nov 12, 2025

tankoamerican said:
very affordable

Wow did you actually make this?

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

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

mmob

mmob

1diesel1

DougV

Natep

PahPahCee

PahPahCee

dazedays

dazedays

lampie208

PahPahCee

PahPahCee

PahPahCee

tankoamerican

WIRING 2x TECs – Max 12.6A​

STC-3028 SETTINGS​

BUILD ​

tankoamerican

WIRING 2x TECs – Max 12.6A​

STC-3028 SETTINGS​

BUILD ​

7munkee

mmob

Privacy & Transparency

Privacy & Transparency

WIRING 2x TECs – Max 12.6A

STC-3028 SETTINGS

BUILD

WIRING 2x TECs – Max 12.6A

STC-3028 SETTINGS

BUILD