Has anyone seen a diy VPD to control the temp and humidity in a tent? I’ve seen a few commercial units but haven’t found any diy stuff in my searches. I could use a temp controller and a humidity controller, but I’d prefer something smart to keep within the vpd range
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VPD is just a function of your temp/humidity. You can use any environmental controls to target a vpd range then dial it in w/ an IR gun and a chart like this:
I’m sure there are units that trigger exhaust/humidifiers/heaters/ac etc etc to target a specific vpd range but I bet they’re big $$$. ACI new ai controller might do this w/ their equipment?
You probably already know this… but seems relevant given the question.
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My thinking is wanting something smart so the tent can stay within ideal vpd within the temp and humidity range.
Mainly I don’t want my space heater fighting to stay at 82f when 72f with higher humidity is similar vpd and similar growth rates
Thanks for the suggestion I’ll check it out
Edit, that ac infinity controller is pretty much what I was wanting, a smarter controller with vpd settings instead of temp/humidity
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Chasing VPD for benefits is aggressive IMO. The guys I know doing it well have there temps in the high 80s. You will get advanced growth until you make a mistake and then you will have more extreme problems… if your equipment is underpowered or your skill set is not up to speed you will just have more problems with VPD in my experience… Cheers !!!
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I have read leaf temps can be different, but they’ve always been a lil below ambient for me. The AC infinity unit assumes this is consistent. Should make things easier, assuming you’re in the same bracket.
The spider farmer does not take leaf temp into account…so it’s kinda worthless during the grow. Works fine for harvest tho.
I probably shoulda gone ACI
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I’m trying to save money by running a dehumidifier more instead of a space heater is all
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Truly running to VPD for a benefit means running far higher temperatures with a lot more humidity. You don’t receive the benefits until you hit the Extream end is what they don’t tell you. And then it’s a fine line before you have problems. Another thing to consider is VPD to help with mass not necessarily quality….
Edit- if you’re not running a closed room with heavy CO2, don’t even consider the VPD to be relevant…
The whole point is to use more CO2 and if you’re not adding it, you’re not even going to see the benefit.
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Jus my personal experience here…but I HAD to run higher temps w LEDs or the plants would stay stunted.
YMMV
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That is true that we run about 80° with LED… but for VPD in that same room, you would be closer to 89° with heavy CO2 a lot more humidity and a lot higher light PPFD. Cheers !!!
Edit- if done well you will see an increase in the mass. But that’s not taking into consideration the quality. Anybody I know running this way is running for profit not quality.
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Very true, w CO2 ya gotta run it to the line. I just turn over the air constantly as ambient co2 around here 450-500ppm year around. They love it around 85° ambient for me
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That’s nowhere near enough CO2 to run proper VPD. You would need to be over 1000 and that would be low side…
UV supplements are on my try list
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I’m not pushing the PPFD to require the extra CO2 without damage 
no issues here
I’m using cheaper LEDs. I don’t like sealed systems as I’ve dealt with mold and this house is OLD.
I’m happy enough
Edit: everyone’s experience is different for a myriad of reasons. In my own personal trials… I didn’t find CO2 to be worthwhile because unless you pushing every other parameter including VPD to the red line, you won’t see significant difference over running it much slower and safer. Maximum difference might be 30% more which is nothing to sneeze at, but with that comes much greater risk of mold. Before I tried LEDs I would keep my room in the middle of '70s but you don’t have the same kind of infrared heat that you do from HIDs…Bud rot has caused me to throw out literal totes full of top buds. So I guess I look at it now more of an endurance race than a Sprint. But to each their own
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VPD is all about stomatal conductance. You can have a vpd of 1.0 at a low temp/low humidity or at a high temp/high humidity and anywhere in between. I agree with @BTYGMO that chasing the extreme end of this require a well dialed room and CO2, but I do think it’s still worth using as a number to relate temp & RH for a home grower. You can be in that comfort zone for your plants w/o teetering on the high end of it.
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Chasing VPD is like chasing the dragon…
It aint worth it, lol.
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Yes. I made potnanny
It installs onto a raspberry pi zero, and interfaces with some Bluetooth temp/humidity sensors, and Bluetooth power outlets.
Allows you to contol things like temp, humidity, VPD, soil moisture…
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Sweet that’s exactly what I was hoping for. Thanks!
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Cool. If you decide to give it a try, and hit any snags during install… just send me a DM and I’ll help get you up and running
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