suggestion for ec and PH sensors

[ranjitha.bm]

I'm searching a PH and EC sensor for my Hydroponics automation project...I searched various websites but some of them were too expensive and not compatible with arduino mega 2560.SO i request all to suggest PH and EC sensor compatible for arduino mega 2560

 

[ranjitha.bm]

I'm searching a PH and EC sensor for my Hydroponics automation project...I searched various websites but some of them were too expensive and not compatible with arduino mega 2560.SO i request all to suggest PH and EC sensor compatible for arduino mega 2560

 

[ghostman11]

i think for EC all you do is have two electrodes spaced 1cm apart, i would use something like silver or gold plated electrodes. i have also seen single electrode EC probes but ive no idea how theese work! as for PH sensors i have looked myself for a decent one but easy and cheap dont seem to mix!! maybe someone else will have a sugestion, there is a project kicking around on the net for a PH controller but i cant find the link, if i do i will post it for you

 

[Mike odom]

you don't need silver or gold electrode for EC. Stainless Steel works just as good, but you need to AC your current flow to stop galvanic effects.

pH probes are neither simple nor cheap...

 

[edeca]

Let's tackle to two halves of your question separately. Firstly what is your budget? What kind of accuracy, repeatability and range do you expect for your price?

Secondly, what do you mean by "not compatible with arduino mega"? Are you looking for sensors that already have code written for the chip?

 

[ghostman11]

on a random ramble around the net i came accross this site https://code.google.com/p/phduino/ it might be worth a look as its all open source

 

[Mike odom]

yes, well, it's easy enough to interface to a pH probe with a preamp, they give a -.144V to +.144V output. The board I designed and built years ago to do a waste water treatment system had 4 pH inputs. I don't believe I even had adjustments for the inputs, if you do the design correctly and pick the right opamps, you don't have to worry about offsets and what not. But you had to buy the probes and preamps. It is very difficult to build a probe. They are not cheap. They are temperature sensitive.

The link that ghostman came up with states that the design seems inferior to a bench tester, but as long as you have a good probe, it is just as good. Plus, as it states, it is interfaceable. But your system is only going to be as good as the probe you buy, so cheap isn't recommended. Plus they are high maintenance. One good part about making your input amps adjustable, is you can buy buffers to calibrate the probes over time. It also states that it has temperature compensation, but on most (good) probes, that is done in the probe. Maybe the design doesn't use a preamp, so the system has to do the temp corrections.

The EC, or electro-conductivity probes, on the other hand, are very easy to build yourself. You feed them with an H-bridge so that you can AC the current. The board we built for our RO unit (I wasn't on this team) had problems because we used the 2N7000 FETs, and they don't like to be connected to the outside world without lots of protection (how little they knew in 1990).