Arduino Diy pH probe - The Planted Tank Forum

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post #1 of 22 (permalink) Old 01-26-2013, 08:32 PM Thread Starter
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Arduino Diy pH probe

Using an atlas scientific ph stamp and AT Mega 2560 arduino. It was really easy to set up and get running (took 5 minutes). I haven't gotten my probe in the mail yet but from running diagnostic commands it works just fine. The next step will be integrating temperature correction and an LCD.

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post #2 of 22 (permalink) Old 01-26-2013, 09:59 PM
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Another project to follow

I should get back to coding; I've been lazy lately.

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post #3 of 22 (permalink) Old 01-27-2013, 08:07 AM
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I just got this pH stamp in the mail, excited to try it out. Which probe did you order?

You should check out the thread on the DIY aquarium controller:
DIY Aquarium Touchscreen Controller
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post #4 of 22 (permalink) Old 01-27-2013, 07:09 PM Thread Starter
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I got a standard bnc ph probe from some shipper in HK. With probes you get what you pay for but it's good enough for our hobby.

The stamp was really easy to set up. The only thing that confused me was that the BNC breakout board had three pins so it looked like VCC was connecting to it. Took me a bit to realize it was a dead end.
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post #5 of 22 (permalink) Old 01-27-2013, 10:04 PM
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Laboratory grade ph kit
price $106

https://www.sparkfun.com/products/10972

Don't forget to calibrate. Setup instructions are with the link.

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post #6 of 22 (permalink) Old 01-27-2013, 10:51 PM Thread Starter
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For me it was cheaper to buy a few packets of callibration fluid than those huge bottles that go bad after 6 months anyways. Also It ended up much cheaper buying a bnc breakout, stamp, and probe and packets separately (around 70 dollars). The arduino mega 2560 and shields and what not added another 44.
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post #7 of 22 (permalink) Old 01-27-2013, 10:54 PM
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Quote:
Originally Posted by Jeffww View Post
For me it was cheaper to buy a few packets of callibration fluid than those huge bottles that go bad after 6 months anyways. Also It ended up much cheaper buying a bnc breakout, stamp, and probe and packets separately (around 70 dollars). The arduino mega 2560 and shields and what not added another 44.
cool, good find but the set up instructions should help you out.

it would help if you tell us how to get the sweet deal. all through ebay?

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post #8 of 22 (permalink) Old 01-27-2013, 11:31 PM Thread Starter
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Yah the directions were all there. Atlas scientific does a really good job at explaining the set up.

All through ebay:

BNC break out and pH stamp were 28 + 8.00 + 6.50 shipping
Calibration fluid was $9 shipped (bought a few packets)
Probe was $17 shipped

I got it all via [Ebay Link Removed]
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post #9 of 22 (permalink) Old 01-28-2013, 02:16 AM Thread Starter
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Just a quick question, has anyone gotten a membrane based CO2 meter to work yet? Like using a gas membrane like a kordon bag, vegetable bag or something like that to work with a pH probe?

I happen to have some parafilm I could get a hold of to try and make something workable with.
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post #10 of 22 (permalink) Old 01-28-2013, 03:30 AM
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Arduino Diy pH probe

.010" or smaller of silicone sheet works great for separating gas from water. I don't see how this helps your ph sensor. Is it a gas sensor?


Sent from my iPad using Tapatalk HD

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post #11 of 22 (permalink) Old 01-28-2013, 03:44 AM Thread Starter
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The idea is to use a gas permeable membrane to hold some 4dkh fluid and use the ph meter to measure fluctations in ph and translate to co2 concentration. Using the membrane increases response time for CO2 measurement.
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post #12 of 22 (permalink) Old 01-28-2013, 04:01 AM
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oh, gotcha. it costs the same to buy a CO2 sensor whose max is 36ppm
or a bit more ($250) for a sensor whose max is 300ppm.

http://aquatictechtank.net/viewtopic...&t=11&start=10

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post #13 of 22 (permalink) Old 01-28-2013, 04:28 AM
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Quote:
Originally Posted by Jeffww View Post
The idea is to use a gas permeable membrane to hold some 4dkh fluid and use the ph meter to measure fluctations in ph and translate to co2 concentration. Using the membrane increases response time for CO2 measurement.
I think I mentioned this in another thread somewhere, but mistergreen was working on this project

Affordable CO2 sensor?

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Eheim Pimp #362 - Eheim 2213 x2, Eheim 2028, Eheim 2217, Eheim surface skimmer and Eheim autofeeder.
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post #14 of 22 (permalink) Old 01-28-2013, 08:47 PM Thread Starter
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Very interesting projects.

I have one question though. It seems that my probe won't work on 3.3V VCC. On 3.3V the readings constantly fluctuate +/- .2pH on continuous measurement. On 5V it's just fine. Is there a reason this could be happening? I think it's like 1 or two things.

1. I'm using a USB hub to connect to my laptop to power the arduino and probe so there might not be enough power to run everything at the stated voltage.
2. My probe which was shipped from china is just inefficient.

In the event that it's a probe problem is there a way to step up 3.3V to 5V in arduino? I'm worried I won't have enough space to run everything. I saw this thing called a logic level converter but I'm not sure that's applicable in this scenario... I don't have a multimeter with me but I guess I could try plugging it into my DC adapter to see if it works alright.

Or alternatively is there a way to split the 5V into multiple connection points so I can run my LCD and my probe.

edit:

I've read that I can split it through a parallel circuit with any number of devices whose total draw is less than 1A so that I don't fry my components. Does that sound right?

Last edited by Jeffww; 01-28-2013 at 09:41 PM. Reason: parallel
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post #15 of 22 (permalink) Old 01-28-2013, 09:59 PM
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you can use resistors to limit voltage and current. Ohm's law. Knock down to what you need for the lcd and leave it at 5V for the pH sensor.

Get yourself a breadboard and test things out first before you start soldering. There's a process that makes life easier.

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