Build your own co2 monitor / control board for $150


Well I just ordered the parts to build a fully programable CO2 monitor and controll.

Here is what i ordered… Im not gonna go into full detail on how to build this thing because with the parts listed….You can build this thing if you know how to or are mechinally inclined enough to figure it out… Its pretty damn easy.

Basically if you wanna get down and dirty with this thing and make it as simple as possible you will need 4 main parts and 2 LED’s if you want some sort of PPM readings. Plus a selection or resistors and transistors and a few other things i think.

The relays used are for american standard of 120vAC, if your in europe or someplace that uses 220v, You will need to replace anything 120v with 220v stuff

1. PICAXE-20M Starter Pack – Part # AXE005U ……… $15
(or if you want you can just buy any PICAXE chip but the 20x pack is easier to test with and has the transistors to power a small relay built in, As well as enough inputs and outputs to controll alot of other things ….. and untill you get it solid, its easy to work with the board)

2. K-22 LO 0-2000ppm CO2 Sensor ……… $110
( (only registered users can se the link, login or register) )

3. Relay with a 5v Coil and something the can handle a load of 120v @ minium of 1 amps. ……… $2-$5
(For controlling the bigger relay or contactor for the reg’s power

4. Single pole Contactor or Single pole Single Throw relay with a coil voltage of 120V AC and a load rating of 1 or 2 amps @ 120v AC $5-$20
(check your CO2 reg for amp requirments )

Now the picaxe chip is a simple to use and program, that accepts almost any analog sensor, inculding our CO2 sensor
(even temp, humidity, light, and the picaxe has a timer… and can use a battery backed up clock circuit for controlling lights… Keep that inmind if you even wanna controll more then one thing. )

The senseair k22 CO2 sensor is the perfect sensor for us. It monitors from 0PPM to 2000PPM right out of the box with a analog out connection that can be brought right to a single input pin on the PICAXE chip. Perfect concentraion sensing for indoor grow rooms.

It will send out a miliamp voltage from 0vDC to 5vDC, depending on how much CO2 is in the air 0PPM being ~0vDC to 2000PPM being ~5vDC.
(barrowing a friends co2 monitor is the best way to calibrate it…. But even if you cant find one… You should be able to get it within reason…

Then after the sensors 3 wires are wired. (5v, 0v, and Analog out )
Picaxe automatically will assign a number between 1-254, Depending on CO2 concentration. when you read the value of the input pin.

So you will do a tiny bit of math to calc. what each +1 incriment incresase will mean in PPM…. You will only need to do this math in your code if you are gonna use a LCD or a few 7 SEG LED displays to show PPM otherwise just do the math on paper and use that number picaxe will assign between 1-254 in your if else statments in your code.

So you the code you would upload into picaxe you would be something like this… and i wont write the real code it ill just explain it… so you guys can figure it out….

if (sensor reading is less then 139)


Turn on output pin 1 AND Turn on Red LED

if (sensor reading is Greater than 209)

Turn off input pin 1 AND Turn on Green LED
You would of course do a few more if else to check if it is inbetween 139 and 209 to turn on a yellow LED if you wanted or something like that….

Now that statement says it would keep CO2 Levels roughly between 1100 and 1650 PPM. I just threw numbers outs but its not that far off from what you might need… Do the math and figure it out for you self.

Now after that we need to connect the coil volatage from the small 5v Relay to output pin 1.

After we do that we need to connect the coil voltage from the bigger relay that switches on and off a hot leg from a 120V lead to the Load side of the smaller relay to control the power for your co2 reg….

Now it can be hard wired to your Co2 reg or what i reccomened is going from the relay or contactor to a 120v Plug and getting a nice project box to mount the curcuit boards to, then mounting a 120v Plug into the side of your box that you can just plug your co2 reg into….

Its pretty damn simple if you know what you are doing……..

Think of all the other shit you can do….
Add a LCD screen to output the exact PPM and be able to adjust PPM settings with just a few buttons.

Add a temp and humidity sensor to maybe try and controll that too.
The co2 sensor is the most expensive sensor… the temp and humitidy sensors are dirt cheap ~$2-$5

Anyways I bought the picaxe controller a while ago so im just waiting on my c02 sensor and LCD screen to get here and i will have my own co2 controller!!!

This controller will have a VERY tight tolerance around 8-10PPM

So for somethings thats gonna cost almost nothing. Its fuckin’ bad ass

Compared to the 3-4 hundred you will spend to buy premade one.

Let me know if you wanna try to build one… or what you think…

Im more then happy to help
Via (only registered users can se the link, login or register)

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