PH Sensor

Using Arduino Sensors
1

I've been asked to look into making an Hydroponics Controller using an Arduino for a local hobbyist magazine.
One of the sticking points is measuring the PH, to enable the controller to adjust it.

There are commercial probes avaialble, but unfortunately as in most things here downunder, the price makes it a significant portion of the total cost.

The probe remains in a solution all the time, so it won't dry out, and needs to be able to keep the system between PH 5 and 6.
It is possible to calibrate and enter a correction into the controller, so absolute accuracy is not a factor.

I was wondering if anyone had experience with or can point me to a cheap source.

Thanks
Mark

2

Have no experience, but maybe http://phduino.blogspot.com/ might be interesting.

3

Simpson_jr

Thanks for that.
It seems most of those links use a commercial probe, and an external amplifier.

The external amplifier is not sweat, but the probe is....

I understand there may be an alternative to a glass probe, but so far I 've either looked at dead ends, or not looked in the right place.

I have to admit its been an education.

Thanks
Mark

4

Here is an E-bay seller that has both interfacing modules and PH probes. Don't underestimate the exacting requirements of the input electronics needed to accurately read PH probes. It's a difficult measurement with a large dynamic range.

http://shop.ebay.com/atlasscientific/m.html?_trksid=p4340.l2562

Lefty

5

Thanks Lefty.

With the NZD the way it is, it works out about NZ$87.
Your advice re range etc is understood.

I'm picking the project will end up with the option to include a PH Probe, due to the cost v benefit for a very small operation.

I'll probably make allowances in the software to manually enter the PH, and have the corrector added by the system.
This makes it expandable and affordable to wider audience.

If anyone else has some other theories to measure PH, I'm keen to hear them.

I guess that measuring PH involves immersing the detector into the fluid, but measuring gravity, pressure and the earths magnetic field, is a dry measurement.

Thanks
Mark

6

Hi Mark

I have some experience with pH. I can tell ya this,...it's not easy.
It involves a lot of math and a tight circuit to get it right (VERY stable voltage's).
I ended up using this : http://www.atlas-scientific.com/embedded_solutions.html
It saved me a LOT of time. Also, it was easy to use.
You can get the probe from anywhere,..if that would help lower your cost.

Jay

7

Jay
Thanks very much for your advice.

When first asked "how hard can it be", I thought........oh how wrong I was.

I think the project will head alsong the lines of the pH probe being an addon feature, with the ability to manually enter the PH reading into the controller, and either have it correct, or the users corrects it themselves.

These are certainly a great option as an addon, and could be incorporated with a few changes.

Thanks very much
Mark