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 cave man style PPM readings.

Plus a selection of resistors and transistors, LED's 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 easier to work with the board)

2. K-22 LO 0-2000ppm CO2 Sensor ......... $110
( CO2 Meter - K-22 LO 0-2,000ppm CO2 Sensor - Sensor product by Senseair )

3. Relay with a 5v Coil and a load rating of 120v @ 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 simple to use and program, it can accept almost any analog sensor, inculding the CO2 sensor we are using
(as well as temp, humidity, light, ect.... and the picaxe has a timer too... and can utiltize a battery backed up clock circuit for controlling lights... Keep that inmind if you even wanna controll more then co2. )

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.

It will send out a miliamp voltage from 0vDC to 5vDC, depending on how much CO2 is in the air
EX: 0PPM being ~0vDC and 2000PPM being ~5vDC.
(you should barrow a friends co2 monitor to hone in on the exact miliamp VS, PPM readings 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 the code you would upload into picaxe would be something like this...
I wont write the real code ill just explain it... so you guys can figure it out....

Code:

if (sensor reading is less then 139)


then 


Turn on output pin 1 AND Turn on Red LED


if (sensor reading is Equal to or 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 or something and loop and wait command so its not checking the CO2 reading a thoudsand times a minute. Because the K22 takes a reading every 2 minutes it would be pointless if you did a check less then once every 1.5 min. I will be coding mine so it does a check every ~2.5 min.

Now that statement says it would keep CO2 Levels roughly between 1400 and 1650 PPM.
(If i did my math right haha its 2am and im high and tired )

I just threw quick numbers out there but its not that far off from what you might need... Do the math and figure it out for you self.

Dont set the PPM on and off settings to close to each other because you dont want what we call "Short Cycling" where the co2 reg is being turned on and off to many times a hour. Its better to keep them a little bit farther apart so it wont wear the selenoid inside the reg out plus the plants wont really notice as long as its all within reason

You also dont want to set your reg really high because if you are only 50-75 PPM short you dont wanna go from being just a tiny bit low in your ppm to way to high because it only checks about once every 2 min.... So you could easily waste alot of CO2.

Now after that we need to connect the coil volatage from the 5v relay to a transistor on output pin 1

After we do that we need to connect a hot 120v hot leg to the common leg of the 5v relay then that connects to the coil of the bigger 120v relay AND the common leg of the bigger 120v relay. So that when the output pin from the picaxe chip is hot, That will switche on a hot leg from a 120V lead to the coil voltage to the bigger relay witch switches the 120 volts then on to a plug of some sort that goes to your CO2 reg

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

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 instead of reprogamming the whole chip99

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