DIY pH monitor

**waack** · 03-07-2013, 03:47 AM

As part of my new discus tank build i decided to build a DIY pH monitor, I have included it in my journal but I don't get a lot of traffic. Anyhow using my electrical engineering student ability (first time it's been useful in the real world) I programmed an Arduino to monitor pH and calibrated using pH4 and 7 solutions. LCD screen came today so I could finally un tether it from my computer and get it in the tank. Result.

I know it's accurate because water comes out of our tap at exactly pH 7, the kit color matches up perfectly and we are close to the water processing plant and they say on their side they aim for neutral output. Also there is drift wood in the tank which may have led to the slight drop.

On a side note 6.95 appropriate for discus if acclimatised or conditioning required?

**genocidex** · 03-07-2013, 10:24 AM

thats very interesting, what sensors did you use for the probe?

**waack** · 03-07-2013, 11:47 AM

I bought an arduino compatible BNC shield, then bought a ~$30 BNC pH probe from ebay. The probe works by detecting changes in voltages through 2 probes and ultra thin glass at the end of the probe. obviously voltage changes due to change in pH are minute so the shield amplifies them and send to arduino. Arduino being open platform can be customized after receiving the reading. The only issue I can see with it is i suspect voltage diff vs pH is not entirely linear, but the equation i used to calibrate it is. But at least i can see if it swings it will be able to tell me that reguardless.

**mrramsey** · 03-11-2013, 12:26 PM

That's cool whack! I have been thinking about doing something similar. I found a good article on the net about a guy that did a whole monitoring setup. pH, water level, temp, feeding, etc from the arduino. I would like to do that but take it a step further. Monitor 2 tanks with the arduino and using the Ethernet shield tie it into my network. Then have a desktop widget to monitor it as we'll as pushing notifications to my smartphone.

**talldutchie** · 03-11-2013, 12:31 PM

In other words, a DIY senneye?

Interesting project. Just wondering something which is probably very silly but how do you know the probe isn't influenced by the hardness of the water?

6.95 for discus? Depends on what they are raised on. Captive bred should be fine. Wild caught it's a bit high. Stendker will love it.

**waack** · 03-12-2013, 04:53 AM

Temperature and hardness may indeed affect the reading you are right, I'm not using it for exact science though. I sure the influence of the hardness of the water is fairly minimal and like i said before the colour on the liquid test kit shows the pH is not quite 7 but pretty close. Even if it is out a bit it will still tell me if there is a swing which as i understand is the most important thing for discus, stability. I will be getting captive bred so I hope it all works out.

On a side note i have noticed when the lights go off the pH reading goes up by 0.2-0.3 to about 7.2 then when lights are on goes to 6.95 again. Can anyone explain this, im thinking maybe something to do with the plants, but they havn't really established yet and are still quite small in size and number

**waack** · 03-12-2013, 04:58 AM

@ mrramsey
i have been looking at what else i can monitor using this. ammonia nitrite and nitrate seem very difficult if not impossible to monitor electronically. I'm looking at setting up a bluetooth module that will send notifications to my computer/ phone if something needs attention. Since i'm looking at LED in the future I'm also looking into controlling that with the arduino. Would also love to be able to monitor water level in the sump and have the arduino adjust the pump accordingly probably another years project though.