Temperature control conundrum (even with arduino)

[VAtransplant]

Hey all. Haven't posted much here in the last year and I miss it. In need of some suggestions though as my veg tent is getting hot as hell. Here are some basics of my situation:

Veg only, not going to bother flowering in this apartment as my lease runs out in ~2 months
Colorado, but still not trying to be obvious with smell / windows
HTG Motherkeeper tent, ~4ft tall/4ft long/2ft deep
Tent in a small 'office' with one sliding casement window
Gas fireplace in house, the second I exhaust out of that window the whole house smells like eggs

So, I write software for a living. I'm pretty damn good with arduino crapola and already built a sweet little unit with 2 temp probes and 2 humidity/temp probes, lcd screen, and controls a 4-relay switch that happily turns on stuff up to 10 amps

As title suggests, even arduino can't help this currently. If I exhaust outside then the gas issue arises. If I open a window enough to have that be the primary intake (path of least resistance) it gets cold as hell and my heat pump runs nonstop. If I duct intake to tent directly, frozen plants (-10F* last week).

Obviously I can do something like exhaust on at 80*, off at 70*, but it takes very little time for the tent to reach 80* again so it's a bunch of on-off fan spool all day and night. Compounding this is that I'm south facing, so even if it's 30* in the morning the office is getting assaulted by heat. There's no easy way to fine tune duct sizes and intake stuff with huge temp swings (Colorado)

All I can think of is chance TWO electronically controlled ducts, with some Y pipes and logic in the arduino... or try hard to find a decent brushless exhaust fan that I can make my arduino control the speed of, intake straight in to the tent and straight out... balancing the speed as needed.

Open to all suggestions, and if anyone is curious about arduino stuff let me know. 100 lines of simple code could change the way you grow though you ideally have a better grow room set up than I. I've posted several detailed grow journals on here and OG before it was nixed, I'll be contributing some wacky shit when I buy a house this spring complete with detailed tutorials for arduino noobs. Thanks much!

 

[delic]

Hi VAt.

Could you use the arduino to control a small intake fan ducted to the outside? I'm thinking when the cab gets too hot the fan goes on to draw in the (currently cold, its winter right?) outside air into the cab until the temp goes down. If you don't want the freezing air going straight into the cab you could make a small lung room. Just a vented box connected to the cab intake with the outside duct connected to it. Would that work in the short term?

-delic

 

[VAtransplant]

Hey delic, thanks for the suggestion.

I actually had it set up like that but the fans I was using in the window weren't strong enough to run through duct and dump somewhere near the base of the tent (but not directly inside). It also had the negative consequence of air spilling out of my den (I guess that could be considered the lung room) and causing heat pump to run more often.

I ended up last night ducting the exhaust fan out the top of the window, and having part of the bottom of the window covered with a reflectix flap. A little fine tuning and I wasn't pulling gas fumes through my fireplace (that I could smell at least, directly in front of fireplace). The pilot light also stopped dancing inward after I made the flap big enough.

Temps immediately dropped and I don't think I'm dumping much if any air out of the den in to the main area of my house. Obviously this has the potential to make the room way too cold, so I'll still have to figure out something with the frequent fan on/off.

Really would like to find a brushless extremely dimmable exhaust fan though. A lot of the ones I've seen screw up below a certain percent of power. With the right fan, I could just have it run extremely low speeds when temps are good, or cut off entirely after running low for a while. When it came back on (say if tent hit 80*), I could start it at 20% power, give it 5 minutes to work, if still way too hot - increase another 40%, etc. That way I wouldn't have a jet engine spooling up every few minutes.

Finding that right fan seems to be challenging though.

 

[Jhhnn]

If you're using a vented hood, you could run 2 fans- one ducted from outside, thru the fan, then the light, then back outside using backdraft preventers both in & out. W/o the backdraft preventers, the bulb may get too cold to fire, depending. That fan runs with the light. positive pressure in the duct & hood keeps odors out of the exhaust. Then another smaller fan just to move air thru the tent into the lung room, which runs all the time.

I had some of this stuff, cut a piece to put over the top of the reflector. seems to help a little-

http://www.yourautotrim.com/thercarpad.html

Highly flame resistant, so no worries.

 

[rives]

I've read that with the new super-tight houses, new construction is requiring air-to-air heat exchangers on forced drafting to keep from losing too much heat when fresh air is admitted. I've no idea what is actually available in that arena since I haven't had any need for it, but it sounds like there might be something there that would work for you. The following links have a bit of an overview.

Also, Fantech has a relatively new line of electronically-commutated fans out that are supposed to have a much broader range of speed control than has previously been possible. I have one, along with a PID-loop temperature controller for it, but haven't installed it yet.

http://www.hvacquick.com/products/residential/Indoor-Air-Quality/Air-Exchange-Ventilators

http://www.hvacquick.com/products/residential/Indoor-Air-Quality/Residential-HRV-ERV

Fantech EC brochure - http://www.google.com/url?sa=t&rct=...=kU9iPCPiDX8g32DqaBwXyw&bvm=bv.61535280,d.cGU

 

[VAtransplant]

Thanks for the continued input guys. Jhhnn, unfortunately I don't have a sealed light setup. I'm only bothering with veg now running 4x55w T5HO 4foot setup. Lease ends too soon to bust out my big guns, but even then, I've been a bare bulb vert guy for a few years. Sad, I probably won't be flowering again until May. The last time I started something flowering was almost exactly a year ago. How depressing, and a first in nearly a decade.

Rives, sounds like some fancy stuff. May look in to it further when I move and can have some larger equipment in my very own/first HOUSE. I may bite the bullet in the next week or so and just get a Hydrofarm 6" inline fan with their speed controller, as the fan itself seems to have excellent reviews and the speed controller OK, most bad reviews coming from non-HF fan owners. At least I know it'll be compatible. I'm currently running a 6" Can-MAX with the three speed switch. Not much to be read about in terms of compatible speed controllers. As ghetto as it sounds, if I can find a knob controller that has more than 3 positions, even if I have to run at 50%+ to prevent motor from overheating, I'll use a $3 arduino servo and mount it and the controller to a piece of wood.

Here are some pics. Tent has dropped to 67* inside so I brought the arduino to the living room for some tweaking before I put it back in grow area. With the intake/exhaust stuff changed, my logic needed to change a little too. The INT[]/EXH[]/HUM[] X or Check indicate whether the relay is on or off. I guess I'll ignore INT since intake is now 100% passive. Humidity, whatever. Not going to bother running my little humidifier anymore since it'd get sucked out the window in a split second.

View from doorway of den. Yeah, it's tiny. And yeah, I hate having that mattress in there. I have to 'make up' the room a little more cause girlfriend's sister and boyfriend are staying here next week. So weak. Not interested in the inevitable complaints, they should have gotten a hotel! The bottom 6" duct is just to direct some airflow to the tent, but a section of reflectix above it is just a flap that pulls inward with negative pressure. Still seems to be enough at current to prevent gas fumes in apartment from fireplace.

Some life in there. These things are going to be monsters and have even more cloned siblings by the time I finally start flowering crap out in ~May-ish. Sour diesel and purple urkel.

4 foot long DIY muffler that I made a couple years ago and used for several of my grows on here. I got an 8" to 6" reducer tonight to put on the end of it, so I could add the extra bit of duct taking it out the window. Can't hear it from the ground since I'm on 3rd/top floor in complex. The sour diesel is super smelly even in veg but I'm happy to be sending the funk outside finally instead of recirculating it in my apartment. Going to just take my scrubber back to storage unit, thankfully it's still in the back of my truck after picking it up (from storage unit) last week. Muffler and that reducer->out the window has helped a lot. The remaining noise is from the fan itself so additional insulated duct work wouldn't make a difference.

Arduino 4x20 screen showing my stuff. Did some custom drawing to get the larger numbers on the far right. They are the average of two temp probes that go in the tent.

Top left ambient is self explanatory, P: is probe temp, T: is other temp probe followed by the humidity reading from it. Then int,exh,hum explained up top.

The relay board and power panel. This is usually cleaned up a bit better but was/am tinkering with it. Switch 1 is normally closed on relay board, and runs in-tent circulation fans, always on. 2 = intake (no longer used), 3 = exhaust, 4 = humidifier (no longer used). Pretty sweet setup, have a few arduino setups + screens + tons of temp and temp/humidity probes now so I'll be going balls to the wall in a few months. All of this data goes to the internet too for immediate viewing via web server. I write iOS/Android apps for a living and have a few quick/crude monitoring things as well when I'm too lazy to type in a URL on phone. Lastly, all of this data is provided real time for the apps/web, but also submitted to an SQL server. The data can be graphed and I can see when temperatures peak throughout the day or evening. Each time the arduino submits data to the web (REST), I grab the temperature of my zip code from Google's weather API. That all goes in to the table too. Thus, I can see that an 82* high streak at 3pm was a result of it being warmer at that time of day. I'll scrap that for another probe that I run out of the window from the arduino later.

 

[VAtransplant]

Just some closure on this until I find the perfect speed controllable fan...

Pieced the arduino back together and put back in grow area, probes in tent hanging in the higher branches, one on each side (4ft long tent). Have timed it out and with outdoor temp of 35* F, fan will run for 7 minutes to reach 72 and then off for 31 minutes to hit 80. Obviously I'd like to keep it steady but until better fan setup, it'll do. That's not as frequent as it was before so I'm happyish.

Dumbed down the info returned from web (will just make phone app be the pretty one) and here's what I'm seeing