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DIY CO2 Controller

Barbara Turner

Barbara Turner

Member
Joined
10 Mar 2018
Messages
469
Location
Aylesbury
Has anyone tried building a DIY CO2 controller, there are some relatively cheap PH sensors for sale.
I'm guessing as my KH levels vary I would need to recalibrate it.
It would be easy enough to have a adjustable KH input and a simple lookup table. Switching the solenoid valve on and off would be simple enough.


https://www.robotshop.com/uk/gravity-analog-ph-meter-kit.html?gclid=CjwKCAjw-bLVBRBMEiwAmKSB80isDMu9Hty2LSrV9e5YQHE9RqyJkacmgOhmVSgJuY26X3uj_5hawBoCwgUQAvD_BwE
gravity-analog-ph-meter-kit-3.jpg
 
Yes in a way

I have a pH controller which sends the on/off signal to my PLC (How to use a PLC to control your fish tank.) which I then use the signal to turn my duel CO2 injection on and off. It basically gets a 1.0 pH drop in about 40mins then it maintains the pH stable for rest of the photoperiod. But I only use the pH controler to get the pH drop then I just have a steady CO2 injection from one reactor. The trouble with pH probes is they are not accurate and your pH will be going up and down all the photoperiod as it switches the CO2 on and off. I have use it that way at first but much prefer a steady injection rate BBS which was set by doing a pH profile.

I would say money would be better spend on a simple pH pen to do your CO2 profile and get the BBS right with enough time pre lights on to get a stable [CO2], the way I have it on my tank works great but it wasnt cheap (link to my CO2 reactor injection setup )
 
I do not recollect any threads at ukaps with a diy Arduino PH controler project.. Tho there are a few around on other forums i remember one from planted tank.net and a few videos about it on youtube.

The probe only in the picture is indeed a pretty cheap and actualy reliable China probe that as single probe comes for about $7 with a refill kit. I one of these in use for over a year now andis still rock solid. So for that price i can't complain. I have used it on a Milwaukee controler, actualy still installed and operational but i no longer add Co2.

I'm not sure if you are realy cheaper with the complete Arduino assambly building the controller, you need much more than the set you show. Since for example the Milwaukee sms122 that is a pretty solid and acurate controller isn't realy that expensive anymore.
https://www.ebay.com/itm/Milwaukee-...036714?hash=item25bc6ccc2a:g:bqEAAOSwRDtZ3Ort

With fluctuating Kh values there is no need for recalibration it doesn't have effect on the probes Ph reading. Calibrating something you need to do regularly anyway to ensure accurate reading. Fluctuating Kh results in fluctuating CO² contents with the same constant pH profile. In this case a pH controller isn't of any help or isn't a valid reason to install it regarding the varying kH vaue. On the contrary actualy you want co2 to be stable and not fluctuating.

:)
 
The sensor I was looking at claims a accuracy: ± 0.1pH, if you set the bubble count only slightly high you might only get it switching off once every couple of hours.
I've just started using 3/4 RO water 1/4 tap water and co2 levels fluxate alot faster.

I wondered about running two solonoids and two needle valves with one as a top up and the second as background but I'm not sure it will help.
 
If you regulate the BPS perfectly it never switches off.. This you can do with using it n conjuction with a drop checker and a Ph profile.. Once you know where you're at you can set the controller 0.1 or 0.2 pH higher than the desired target. But it will never reach this target since it's set higher and thus never switch off. It'll ony switch off if the BPS exceedes the target value. Or if the controler needs a recalibration, tho personaly in the 2 years i used it it never happened, did a weekly calibration anyway at each water change.

This way the controler gives you a permanent pH reading and works as a fail safe in case of a tank dump it switches off and not as a permanent controller to regulate co2 administer. And it shouldn't be used for that, it is not a easy going laid back automation device to forget about CO². It should be installed with a timer switch on the solenoid as a fail safe and a permanent on the fly pH reading.

A tank dump also can be prevented with buying a more expensive dual stage regulator.. Tho not so log ago a UKAPS member still sufered a tank dump with an alleged duall stage, the vendor was awfully sory and appologized rectified the issue, but still all his fish were gassed and dead. That's quite a shitty situation trusting on technical equipment and when find out it fails it;s to late.

Than you can ask yourself the question are you beter off with a cheaper single stage regulator and a controller? Both added likely are equaly expensive as a dual stage regulator.

That's a question everybody has to answer personaly for themselfs regarding their budget and believes. In the 2 years an 10 litre CO² i used with it, i still monitored it closely every day. And it actualy served me pretty well. I can not second all the horror stories giong around about pH controllers.. I honestly have no idea why, with what and how the people claiming it ran into the problems.. They probably used it differently than i did. And blame the device.

Using 2 solenoids on one controller? I can't see why this would do any good.. If one controller controlles both than they both switch off at the same point.
If you have one solenoid controlled and the other not than i stil can not see the point of it.. No idea where you are going with this.. :)
 
Last edited:
Barbara Turner said:
I wondered about running two solonoids and two needle valves with one as a top up and the second as background but I'm not sure it will help.
Click to expand...

Basically thats what I have done with twin CO2 reactors, twin injectors gets the pH drop fast then one switches off and one just maintains the [CO2]. I personally think its a better way of doing it esp on bigger tanks. Small tanks with low BPS to get target pH not worth the cost as even with the CO2 coming on 3hrs before lights my 6.5Kg cylinder has lasted over 9months on my 50L tank. But my 500l Tank a 6.5Kg cylinder lasts about a month
 
Thanks everyone for your detailed responses, there is some interesting things to think about. it becomes an expensive safety device if you get the bps perfect.
I must confess I never assumed the JBL reg / needle valve I have to be that consistent or adjustable.

Is there a clever way to get from your pH profile to working out when you turn on and off the co2?

Does anyone know why you get a co2 dump is it normally reg failure?
 
You could use a pH controler, but it functions easier without one,
1) don't be scared by pH drops, fish don't mind them, why should you :p (ph drops due to CO2 are "weak acid reactions" they are virtually harmless, unlike strong acid reactions wich are bad bad bad; you would drink a glas of cola( weak) but not a glas of batery acid (strong)) (Too high CO2 can give breathing problem for fish though)
2) what the plants need, and what we want, is a high level of available CO2 which the plants can use when the light intensity goes up. To deliver that we start CO2 before lights are on, so when the lights go oon we have the maximal amount of CO2 dissolved. This we keep up for 4-6 hours then we stop CO2, the plants wont use more so no need to keep dosing.
3) to get the correct amount of CO2 in we just start dosing 30-12- min before lights on ( depending on your dissolving capacity) and shut it of after 4-6 hours. No need for fancy controlers, a simple on and of will do:D:D
 
Edvet said:
it's just extra stuff in and around the tank there is no need for
Click to expand...

That still doesn't make it difficult. :).. There is also no need for a sunrise sunset controller for the lights. I never heard anybody say not having one is easier which actualy is more true than saying a ph controller is difficult..
 
Barbara Turner said:
Does anyone know why you get a co2 dump is it normally reg failure?
Click to expand...
End of tank dump is generally due to a cheaper/poor quality regulator. A lot of cheap regulators are in fact not regulators, but technically "flow controllers". They reduce the pressure by reducing the flow via either a pin hole or restriction or metal sponge. These work fine when the pressure difference is constant ie tank full and CO2 output on, but as the tank pressure falls they loose regulation and end up emptying the remaining contents of the CO2 tank into the tank. This is acceptable when in the tank when CO2 source is a small disposable canister/bottle where only a couple of grams is dumped, but when used with a 2Kg/5Kg CO2 cylinder this dump can be a considerable amount of CO2, pushing in tank CO2 ppm way above the considered safe of 30ppm, thus gassing your fish!!!

Some single stage regulators are reported to do this as well. I have a single stage regulator and as tank pressure falls the bubble rate starts to drop, but certainly doesn't empty the CO2 tank when pressure gets low.

Dual stage regulators do no suffer from end of tank dump and maintain regulation as tank pressure falls which is two plus points for a dual stage regulator.

As for CO2 controller. A well set up needle valve, bubble counter and correctly angled spray bar negates the need for any high tech controller.

On saying that you might be the first person to not kill his plants/suffer melted plants/convert his tank to algae using a CO2 controller we have met, we wait to see your results. :D
 
Barbara Turner said:
Has anyone tried building a DIY CO2 controller, there are some relatively cheap PH sensors for sale.
Click to expand...

Hi,

Was looking around the forum to see if anyone had done a basic micro controller for the planted tank, partic the Arduino and noticed this thread.

Wondered if you or anyone else had done something to meet your needs ?

I have a couple of controllers I programmed for my old marine set up, nothing fancy, just basic timers and temperature controllers. alarms etc though one version did have a ph board/sensor.

Am about to build a basic Arduino based one for my new 55ltr planted tank, starting off with the basics, like temp control, min.max recorder, simple on off light/ led timer.

Be interested to know what other automatic functions you and others think would be useful .
 
You could do auto top off and/or automatic water changes, timed dosing of ferts. These the sorts of suggestions you want?
 
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