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Arduino based climate controller

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#1 Acidictoes



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Posted 09 March 2019 - 08:25 PM


Im pretty new to growing, and i dont have time to mist and air my chamber when i should.

So I made this climate controller to help me get started with my growing.

Its still a prototype, and I still add`s features. so it would be nice with some thoughts and ideas :)

This is an entusiast project, i`m not a coder, but i can make it work. Maybe someone have some coding tips as well :)

So far, it kind of work(two fruiting cycles so far)

I have some tweakes and new features planned.

So far it controlles;



*CO2 level






    Humidity has two settings, Low and High. it will try to hold the value between those settings


              When humidity is under low, the ultrasonic fogger will engage

              When humidty is over high, the fan will let in new air.

              Between, nothing (just 20% circulation fan, to circulate the air)


*CO2 Level

    CO2 Level has one setting, ppm level. It will try to hold the CO2 level under the limit.


             When CO2 level is higher then threshold set, change air.



       Temperature has two settings, Low and High. it will try to hold the value between those settings


              When temperature is under low, the heater will engage.

              When temp is two degrees under set value, it will alternate the heater 2 sec on and 2 sec off. this to not overshoot (This may be changeable setting later)

              When temp is over high, the fan will let in new air.

              Between, nothing (just 20% circulation fan, to circulate the air)



     The fans has 3 settings.

        Circulation fan speed, New air fan speed and change air interval time

        The fan speeds can be set from 0 to 100%, and the "change air interval time" can be set from 1 to 360 minutes(6hours)

        Circulation fan will engage when fogger or heater is on, else it will stay on 20 %(may become adjustable)

        New air fan will engage when any alarm is over high threshold

        When "change air interval time " hits is target, it will set the new air fan at 100% for 30sec (This one may be adjustable later)


All alrms has an indicator at the homesceen, its 3 squeres.

If the squere has a dot inside, its under low value.

If the squere has a ring outside, its over high value.

The interval time is displayed at the homescreen as, minutes left and inteval time

The low and high settings is also displayed at the homescreen in the bars (high is thicker then low)


Thinking about to make the set button on the homescreen to engage the fogger.

I dont think i need a timed interval for fogging, couse it will fog everytime time the change air interval gets humity under threshold. 

Maybe a light interval controller.


Im sure there is a lot of things i havend described here jet, i think i will see if there is any response before i go further :)


some pictures from the project;






If anyone is interested in this project, i will be very happy too hear some thoughts and ideas around this project.

Maybe it could be an open source project :)

Attached Thumbnails

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Edited by Acidictoes, 09 March 2019 - 08:33 PM.

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#2 RutgerHauer



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Posted 09 March 2019 - 08:45 PM

Awesome, great job! I came to know about arduino through music/sound programming and have fiddled around with it, but this is also a great use of this open technology. Cannot give you any tips, but I am happy to follow your project. Good luck!

#3 mushit


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Posted 09 March 2019 - 09:04 PM

Great project!

I am designing a temperature controller for my beer fermenting chamber.  Around the same ideas you are describing.

The circuit board I designed uses the barebones Atmega with the required connections.


Are you driving relays or SSR's with the Arduino?


What type of board is that in the pic?

#4 Acidictoes



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Posted 10 March 2019 - 02:59 AM

Thanks :)


Its an Atmega328p, Arduino Nano board.

I use simple relays to control fogger and heater.

and a integrated max1515 IC (motordriver) to control the fans

#5 Acidictoes



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Posted 11 March 2019 - 09:48 AM

Had my first real problem with the system today...



When co2 is over the set threshold, it will blows out the air to get new fresh air.

And when the humidiy gets below set threshold(cause of blowout) it will engage the fogger to behold the humidity.

until now this has worked fine.

One cake was newly dunked.

after that the co2 level is way higher then before, and cant get it to "normal" level again...

so the system is constantly blowing air out and rehumidifying the chamber.

Its overfogging a lot...


i have disengaged the co2 threshold for now, and may dump the whole idea of the co2 sensor function as well.

Maybe the timer based blowout is enough..?


The co2 sensor that is used is not a dedicated co2 sensor... its a relative air sensor. mq135

Dedicated co2 sensors are expensive, mq135 is very cheap.

Mq135 can smell co2, amonium, alcohol and other gases as well.

So the "high co2 level" can indicate that there is a contaminated going on.

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#6 RutgerHauer



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Posted 11 March 2019 - 01:46 PM

If you can read out alcohol you might be able check for yeast contaminations.. but that is also an obvious smell..

Can you go the other way around and check oxygen? Since that's what they need..

Edited by RutgerHauer, 11 March 2019 - 01:47 PM.

#7 Acidictoes



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Posted 11 March 2019 - 03:23 PM

the sensor is really sensitive to alcohol and ammonium compared to co2.

so very small amount of alcohol gas can give the same result as high co2.


the plan was to have two air sensors, one at the outside, and one inside the chamber. compare the result and have a setting to change how much differense is allowed.

I`ve started to see for oxygen sensors at first, but found them too expensive for a function i dont know how nessesery it is.

then i looked for co2 sensors, same story...

and ended up with this mq135 sensor


I still cant make my mind...

maybe i  just let the sensor stay, and remove the threshold fuction, nice to see air quality.

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#8 Myc


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Posted 11 March 2019 - 04:45 PM

I think your earlier post had it right. If you're trying to control a very small environment - less than 36 cubic feet - you're going to experience rebound difficulties unless you can dial-in a serious number of variables. 


The simpler approach would be to create a two-pole timer. 

One section to operate the "fogger" just long enough to humidify the enclosure without causing saturation and condensation. Otherwise, you'll have pooled condensate to deal with - as you've noted, the fogger uses quite a bit of water. 

The other timer section to operate the purge fan for Fresh Air Exchange (fanning).


Most guys who just mist and fan will advise 3 times a day for FAE and misting just after fanning. 

You could arrange a simple 3-part or 4-part timer cycle around a 24 hr scheme without being too complicated. Your biggest challenge will be deciding the running duration of the fog so as not to overwhelm the enclosure with condensate. 


In a larger cabinet - say 36 cubic feet and larger - you could arrange your sensors as "alarms" to detect the excessive presence of co2 and other gasses or to monitor for low relative humidity. Either of these "alarms" could trigger a timer cycle override to temporarily mitigate the conditions until you have time to check. 

You may also find that humidistats can be inaccurate and are easily overwhelmed by 100% humidity (as in while the fogger is running). They don't last long in high-humidity environments - but seem to do OK in larger enclosures. 

Edited by Myc, 11 March 2019 - 04:48 PM.

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