My Instrumentation and Control System

Hi Folks,

My control system has matured enough during my first 3 grows (just started the 4th) so I thought I would share it with everyone.

Everything is controlled by one of those programmable microcontrollers (NodeMCU). It has built-in WiFi that communicates with my PC in my living room. I can monitor environmental conditions and make changes to the setpoints and lighting schedule remotely. It periodically logs all the data to a file so I can go back and look at the history.

It is very impressive what the little boards can do.


Mate can you please elaborate more on how to make or where to learn this stuff? Ive spent hours going over microcontrollers, solenoids and smart home integration into the grow space but other then $500+ systems there isn’t much I could find detailing what was only imagined possible 10 years ago. Being able to track, chart and control with minimal physical supervision is the ultimate goal of any indoor garden


I have found the rabbit hole, Sonoff Smart Switch for anyone else curious. I now know how much these $2000+ environment monitoring systems with apps are actually worth. Interest to still hear your input


I use the NodeMCU which is an Ardunio type development board. Cost is about $5 or so.


It has lots of pins that can be programed to do different functions. Such as inputs and outputs. And it has built-in WiFi which is golden.

If you are just starting out; the NodeMCU and a decent temperature/humidity sensor like this:

Model: HTU21D-F sold by Adafruit. It has good accuracy and costs about $20. I wouldn’t go too cheap on your sensors, if they aren’t accurate they aren’t any better than having nothing and possibly worse.

Once you have this up and going it is very easy to add sensors and expand your setup.

This is really nice work. While not for those who prefer hands-on gardening, you could market something like this along with the list of compatible systems it controls including setup instructions geared toward the micro home grower on a limited budget.

Thanks for the compliment. I am sorta a geek with this kinda stuff. I have just started my 4th grow so I am a little over a year into this. The technology has definitely made it easier for me to see the big picture at a glance; but I still have a lot to learn about basic growing. My recent harvest of 3 plants about 36" tall gave me 9 ounces of finished bud. I am shooting for 12 this time.


What sensor are you using for your dli input?

This is amazing! Thanks for the share

1 Like

Thanks! I don’t have a true PAR meter so I am using a LUX meter and lots of measurements and calibrations to convert that reading to PPFD with my lighting current lighting. Can’t afford a PAR sensor yet.

So basically I use the equation:

DLI = ((Average intensity over a 24-hour period, in μmol·/m2/second) x (3600 x 24)) / 1,000,000

Since my software controls the on time of the lights, it uses that value in my calculations.

I just added that function along with the CO2 a few days ago, I think I got the math right and over time I will be able to confirm it

I could be mistaken but I think it’s based off the length of time your lights are on.

This is all amazing tho

This is the light sensor I use:

My research shows the LUX reading is pretty accurate, and comparing it with my handheld LUX meter they both read close to the same


Yes, you are correct so the lights on time is controlled by my software (18 hrs) so I take the PPFD x the 18hrs then divide that by 24hrs to get a daily average. I think that is the right way to do it.

Don’t let the gizmos get in the way of giving the plant what it needs to thrive and take the harvest it gives you.

While 9 oz from 3 plants ain’t a bad thing, pushing yield can be detrimental to quality. 3 oz of high quality per plant trumps 4 or more oz of sub quality per plant.

  • Get a sensor to place in the soil to determine pH and moisture level and another one for nutrient detection. One channel for each plant.

  • You also need leaf temp for VPD.

gotta rush off to work now, can we continue this conversation later? I could use some more input from someone with your experience.

So just to kinda of pick up where we left off. I absolutely agree with not letting the gizmos get in the way of things. I try to do the math as best I can and temper it with a good dose of common sense and experience. Still working on gaining the experience though.

I tried a couple of different soil moisture sensors and just couldn’t get results with them so I scrapped them all together. I now use digital scales under each plant to keep track of the moisture levels. sort of like the lift the pot method to gauge if they are dried out.

In my first post, my dashboard; the three center gauges are the weights. Here is a picture of the scales:

It was a little tricky to do because I have everything on a carousel so I can rotate the plants to my opening and not have work over things to get to the plant in the very back.

An added bonus is I have three solenoid valves, one for each plant to feed and water. I enter amount of water in liters, 1 liter = 1 kilogram for each one and once the scale increases to this amount it shuts off the feed to that plant only. And will continue with the others till they reach their correct dose which could be different. I grow three different strains. I still have a few bugs to work with it but it works reasonably well.


How much actual programming is involved

Hi Bob,

with all my sensors and calculations I probably have a couple thousand lines of code for the MCU part.

I won’t lie to you, I have a lot of time in programming. I am not a professional, and don’t work in a field related to computers. It is just something I like to fiddle with.

To make the temperature/humidity sensor work takes only a few lines:



Very nice work. The weight of the pot is a good indicator of grow media moisture content. Now a pH meter…

Ck out some of the hydro grow sensors that add nutrients to the reservoir automatically. It could give you some ideas. …but the 1/4 C dry organic amendment every other week works just as easy if you top water. You still gotta get to the grow to visually ck the plant so top water and dry amendments are a nice interaction.

I will for sure check out the hydro sensors you mentioned. This last grow was the first time used ocean forest with a few different amendments, worked exceptionally great… all I had to do was water until about the second week of flowering when I had to supplement with liquid nutrients. I probably should have started a bit sooner because the first couple of weeks flowering really seemed to use up my nutrients. That is experience part I am still working on. I like the idea of just dry amendments throughout the entire grow and will check into that. I am sure I will have questions and hope i can reach out to you for advice. This is still all new to me so I find myself sitting just admiring them all the time.

Alright so I understand board → sensor and that gets relayed to WiFi where you can read outputs and the data logger to help backup information to be able to pull it up overtime but…

What did you use to adjust lights? Is there a plug adapter?

Sorry so many questions but I took a deep dive into this and am seeing how I can adjust my current system to include as many of these features as possible:

Lights monitoring - dli

Light controlling - dimming, timing, sunrise/ sunset function

Air quality monitor- temp , rh , vpd

I know I gotta start small n slow, so I’ll add lights monitor and build off that…dli conversion is not my strong suite and I hate sitting there with a photon app trying to read my phone as it get hit with the qbs

Would it be possible to put it between a power strip? Allowing the current to flow thru the board and then limit the amount of power drawn dependent upon the amount of light wanted to be used?

Does that make sense

Cut power cord - + ground, connect that to board and allow resistors to regulate according to programming function ?