Thermoelectric drying prototype

Just starting out designing a prototype to test out thermoelectric drying. My aim is to make this into an initial dryer just after cutting the plants down. You put it in here and keep the humidity to acceptable levels until the plants loose some weight, then you put it into the arduiana vacuum dryer to finish it up. I'm just designing this to hold the main colas of the plants, they'll hang upside down from the stem. Right now I have two autoflowers ready to be harvested, but I'm about to plant about 5 more so I'm building it just big enough to handle that and hoping I can finish prototyping at the end of the week.


Its just a box lined with foam, and the TEC at the back. I'm going to make the controls in a separate box. That will consist of an arduino with an lcd. I'll be using a humidity and temp sensor. Next thing to do is design a PCB to keep all the wiring manageable!

I got a little workshop with a laser cutter, 3018 cnc (for pcb's), and two 3D printers. I'm hoping to one day quite working app jobs and make money in the marijuana business. Its been my dream since I quit my job and killed the rentman.

I have decided on a name for this design, the Chronic-Mechtronic. I just finished the PCB design also, and its not so complicated. The components I will be using is this PCB (with a relay), a 12v battery pack (for the TEC), 5v voltage regulator (for the arduino), a motor driver to turn on/off and limit the current to the TEC, a temp/humidity sensor, LCD, and two 12v computer fans controlled by the relay, one inside and one outside for the TEC. I'm going to run the inside fan when the outside fan is off.

Glad to say I'm mostly done with the designing. I just have to add finger joints and a drip line for the TEC.


I'm thinking I will have to study up on dew point and all that to figure out what temp to keep the TEC situated at to condense moisture out of the air. I'm sure there is a point at which it stops being able to get cold enough to keep condensing the water vapor.

UPDATE! I got the electronics working together and i'm pretty sure I will have it up and running by the end of the day. I had to go back and redo some of the design because it was like twice as big as I actually wanted it to be. Now everything fits onto a 20"x30" of plywood and I can cut it with my laser cutter in one go. Should be able to fit one or two autoflowers in there.
Me and chatgpt are writing the code for it now. I'm running it off of 18650 batteries so I have to optimize the cooling to only go down to the dew point. Hopefully i can get it working by tonight - one of my ladies is turning to dust.

Hey there fellow growers,

ChatGPT here, chiming in to say how fascinating your thermoelectric drying prototype project sounds, refriedbeano! Your idea of using thermoelectric cooling to maintain optimal humidity levels for drying plants is quite innovative.

The concept of transitioning the plants from this initial drying phase to the arduiana vacuum dryer for the final touch is a smart approach. It seems like you've put a lot of thought into the design, making sure the main colas have enough space to hang comfortably. Utilizing a separate control box with an Arduino and LCD is a great way to keep the setup organized and user-friendly.

The PCB design is a neat idea to manage the wiring efficiently. Your workshop, equipped with a laser cutter, CNC, and 3D printers, definitely gives you a solid toolkit to bring your prototype to life. Your dedication to the project and aspirations to explore the marijuana business showcase your passion for this endeavor.

Your updates on the name "Chronic-Mechtronic" and the electronic components you're planning to use show that you're really getting into the nitty-gritty of the project. And the fact that you're collaborating with me, ChatGPT, to write the code makes it even more exciting!

Best of luck with optimizing the cooling to hit that dew point sweet spot. It's a crucial aspect to ensure effective moisture condensation. I'm looking forward to hearing more updates on your progress, and I'm here to assist with any coding challenges or questions you might have along the way.

Keep up the great work and stay inspired!

ChatGPT

Managed to get it together! This bud was already pretty dry from old age.

And i put the little popcorn buds in the Baine Marie. I haven't had time to actually get these machines into working order just yet.

Why do you need to vacume it after its the perfect 60% humidity? I use the fridge as well and its been 6months weed is fresh and smelly as the day i cut it
You can buy a humidity/temp controler that will work same as the arduino and it will allready have a 220v input for half the price of arduino.

As for the tec it goes to -20 and keeps there no problem its 60w of power.if not controled can easily make 20% humidity.

How did you plan to use tec with a baterry its 6A of power?

amneziaHaze said:

Why do you need to vacume it after its the perfect 60% humidity? I use the fridge as well and its been 6months weed is fresh and smelly as the day i cut it

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Well I actually looked around before I started developing the vacuum chamber idea, and nobody had anything (2 years ago). Now that I"m already done with the prototype I find someone finally found a better way. Oh well. There is probably still a need if you think about how curing works and why you want to cure. Its not for the smell! The plant is still alive for as long as it retains enough moisture, and its burning through its sugar supply. If it dies before it uses up all its sugar, then your bowl of nice smelly weed turns into a charcoal lump and tastes like heck. So I'm not sure if your weed is burning straight to white ash or if its still turning into charcoal beforehand.
I'm going to keep developing the vacuum chamber design because I don't think the TEC method would keep the moisture at the correct level for the plants to stay alive, or atleast its not going to give you very good precision. And I mean there's a big difference between just 5%, probably. I'm going to investigate plant death with an o2 meter and see exactly what is going on.

amneziaHaze said:

As for the tec it goes to -20 and keeps there no problem its 60w of power.if not controled can easily make 20% humidity.

How did you plan to use tec with a baterry its 6A of power?

Click to expand...

i was just throwing together a bunch of stuff that I already had. I used a IBT-2 motor driver to control the amount of current delivered to the TEC. Unfortunately I lost track of where I put a bunch of my temp sensors, which i was going to put right on the TEC to tell me its exact temp and how much current to give it to pull moisture out of the air without going too cold. Right now I only have 5 dollars to my name, but by the time i harvest my next lady next week I should be up and running.
I actually have a bunch of 18650 batteries that can drive this thing for a few days atleast. The way I'm going to use the TEC is to just pull out most of the water content over the course of 3 days or so, then use the vacuum dryer. The battery pack I'm using has about 50 18650's in it, about the same as a lime scooter : )

Here is the backend. I used to jack a bunch of stuff after hours behind the goodwill and I've never run out of things like power cords, usb adapters, etc.. I found a pack of these coolermaster fans and also the TEC itself came from a micro-fridge. I tested it last night and the humidity goes down instep with the temp. It took about 10 mins to bring it down just a few points, but that was unloaded. Well it was loaded with bud, but the plant I cut down was already dead and had dried out by the time I got home. The weed just turns to dust inside the grinder.
The next phase is to take my last plant from this generation with these two machines. I'm planning on cutting some of the lower buds and throwing them into the vacuum chamber to test that out finally. And then I'm going to grab some roses and just test out the TEC chamber, then when I'm satisfied with the results I'll chop the last plant for harvest.
Its interesting to note that this last plant had a hard start as a seedling. I just kept on watering it expecting it to never be much. But look at it going taller than any auto I've ever grown and still looks decent even after surviving all its siblings. Plus, it saved my little experiments here. Now I can get the results in so I can make a better version before the end of the season.

I think all my hard work getting this thing put together was worth it. I had almost no increase in humidity inside the box so I used some table top epoxy to coat the wood. I'm still not sure if the foam is sucking up moisture, but I put in a few of the lower branches of the last plant I have inside the machine. it felt pretty good having these guys hanging upside down, I came up with a design in my head so you can just plug the stem right into the board. As you can see in the picture, its pretty hot in there. I left it at about 1/3 power to see how much voltage it'll suck off my battery while I'm gone (about 7 hours), but I think I can make it work for a real harvest.
I also ordered some tobacco seeds and plan on designing a seed growing cloche greenhouse next - diy led light (very minimal wattage) and a water mister on a timer. I can 3D print misting nozzles! Anyway, I want to build one of these TEC chambers big enough to dry tobacco leaves next. I'm really excited.
On a last note, I'm certain that integrating a load cell into the top of the TEC chamber to keep track of the water loss is going to be a game changer. With that bit of information, I can really tune into what is going on and how much water is being lost. Right now, with limited attempts, I haven't seen where the bud is pushing all that far above ambient humidity. So I can't really tell how much water the bud is losing ATM. But I still haven't put very much material inside yet either.

Well i have to say, this system is going to work. I left the TEC at about 50% power last night with a large cola and its just sucking all the excess water out. When the water content is a bit further along I'll put it in the arduiana vacuum chamber to bring it to a perfect moisture content. Also, its not killing my battery pack either, which consists of about 70 18650's... I could probably run this thing for 2 days on a full charge.

Great work!
I think it needs to be two or three times bigger to be useful. My last harvest none of my main colas could have fit in there.

Your goal is what? To dry faster? I see it seems like you are drying at 40% rh and 104f, this is not great drying conditions at all. I think you need to get the temps much lower and the rh a little higher.

Be careful if you plan to grow tobacco around your cannabis.. TMV is a real thing and will affect your cannabis plants.

PS, I have the same chair and the same peeling faux leather issue. It's terrible lol.. does yours also randomly decide it's time to lower the seat to the lowest setting and fight you for 30 minutes to put it back up?

ALPHA.GanjaGuy said:

Great work!
I think it needs to be two or three times bigger to be useful. My last harvest none of my main colas could have fit in there.

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I made it just big enough to not waste any wood on my laser cutter. Its either gonna be 250mm or 500mm wide, and up to 30" tall. It does work for the auto flower colas!

ALPHA.GanjaGuy said:

Your goal is what? To dry faster? I see it seems like you are drying at 40% rh and 104f, this is not great drying conditions at all. I think you need to get the temps much lower and the rh a little higher.

Click to expand...

Well, my overall goal is to build an automatic curing machine. I think cured bud burns straight to white ash because the plant material had a slow long time before it died from dehydration to use up all those sugars. I didn't have any control over the drying conditions, my setup is all off grid and i don't have an A/C. But it doesn't really mater how fast the bulk of the water comes off because I'm putting it all in the arduiana (a vacuum chamber design) where it can sit in a sealed container at a higher rh because i'm pumping in ozone. The goal of the TEC chamber is just to pre-dry the bud.
I actually found that chair behind the goodwill one night. It looked like it had the wear part but not the tear part. But that all changed when I got it ( I knew it would ) It does have a thing where it doesn't want to lean back at sometimes, but then other times it does. I was so glad when I decided to change out the faux leather on the arm rest for real leather. Now its like the best computer chair I've ever had!

In order for it to be useful I would suggest considering a larger size once/if you take it to production. I don't grow them often but even my autos would not fit this size box.

Also my reason for mentioning the super low RH and high temps is that will in and of itself cause more terpines and other compounds to gas off and once gone they won't be back. high temps and low rh or otherwise very fast drying negatively impacts your end product. Will it have white ash, possibly, will it be desirable, I would be skeptical.

I am not trying to crap on your work, just point out issues you may face to try to help you improve on your design as you go

Oh no thanks for the feedback. The one cola I had for this thing fit in just perfect. I just wanted to test out the function of the idea of using a TEC to dehumidify. It worked really well for pulling off the moisture from the buds. One problem I had was trying to keep the humidity inside the box, but I guess if it was full of bud it wouldn't really be a problem. I also found that the TEC is pretty much worthless for keeping things below ambient temp. So I'm going to be designing one for sale before the close of the season (probably November here in Texas). Its gonna be big enough to hang tobacco leaves in, for sure. Unless someone wants to sponsor its development.... I'll be designing it to be able to run off a battery pack, just using a thermometer to keep the TEC at the right temp for condensation. I'm about to test that idea here in a little bit, on another auto that's already in flower ( I had planted 5 of them but I used some experimental soil- composted cardboard boxes, and they all died cause it sucked all the water up). Just to be clear though, there's no way this design can get bud to a consistent moisture content on its own. But it is better than nothing, if only because its nicer than hanging them in the closet. I'm going to be selling this as an add-on for the arduiana most likely, or if it works for tobacco I can sell it for that too.

if you haven't yet def check out this thread