Backyard Aquaponics
A place to discuss aquaponics

That isn't a reference to something in particular, just a knowledge of how these things work.
Even the ones that directly connect to a pc give a millivolt output, its just that they also have the electronics to convert that to a digital number (and send it over USB) the special software on the pc can read. If you just bought the probe itself, without the fancy electronics and software, you could program a micro controller to do the work for you.
A project definitely not for the electronics/software beginner.. although I reckon someone with a Bullwinkle level of dedication could get it sorted out

even if your water level varied, you could just drop it in on a float. so it would always sit the same no matter what the level.

These probes are actually quite complicated.

An ion-selective electrode (ISE), also known as a specific ion electrode (SIE), is a transducer (or sensor) that converts the activity of a specific ion dissolved in a solution into an electrical potential, which can be measured by a voltmeter or pH meter. The voltage is theoretically dependent on the logarithm of the ionic activity, according to the Nernst equation. The sensing part of the electrode is usually made as an ion-specific membrane, along with a reference electrode. Ion-selective electrodes are used in biochemical and biophysical research, where measurements of ionic concentration in an aqueous solution are required, usually on a real time basis.

http://en.wikipedia.org/wiki/Ion_selective_electrode

Here is a nitrate probe designed for ponds etc.

http://www.fishlab.co.uk/nitrate-nitrite-testing/nitrate-probe/prod_10.html

Expensive as hell, BUT you could make it work, then you need a nitrite probe, ammonia probe, ph probe...

I imagine the automation of a probe like that would be very costly and time consuming. lol

It is also a shame they are so expensive. Not the sort of thing you want to make a mistake with. haha

indeed

I have an idea...

"add 10 drops of solution 1, shake for 30 seconds, then add 10 drops of solution 2, blah blah...."

Chemistry! That's off topic

haha. Lazyness is the mother of invention

Besides i dont want to have to take a sample every 5 minutes like i can with a data logger.

see above

Great information, I have learned a good bit thanks. Now one more thing to add to my imaginary system. Time to stop gathering info and start building

Here's one, not much information on it, except that it is a mV output.
http://www.fishlab.co.uk/nitrate-nitrite-testing/nitrate-probe/prod_10.html

I admit to not having researched it a lot after I saw the prices of these things.

I did however work for a company that made a blood analyser.
The probes, algorithms and subsequent code were highly complex, way beyond the average programmer, me included, they had real life professors calculating the algorithms and in the 18 months I was there, they still hadn't perfected it.
I think simple single chemical probes would be a lot simpler, but probably still hard work.
At least for worn out, old hackers like me

You need to measure conductance, not resistance, Google "EC probe" - but nothing I have read suggests it would be useful to AP, doesn't mean it isn't, just means I haven't read it yet



Someone (I think Gemmel) suggested using the colour strip tests, you could dunk them in the water from time to time, take a picture, run an FFT on it and get a digital result.
That would be doable with a webcam or any old digital camera with a remote control.

Hi!

Why dont you use digital sensors? / instead of analog /
If you want to use the arduino to controlling some other process, /paralell the datalogging/ maybe the analog inputs wont be enough...
And you can use the digital sensors in one digital i/o . More sensors in one channel, in one wire.


Here is a tutorial about the digital sensors for arduino:

http://www.hacktronics.com/Tutorials/ar ... orial.html

http://www.hacktronics.com/Tutorials/ar ... orial.html

http://www.hacktronics.com/Tutorials/ar ... inder.html

Hi katona.
Reading temperature is no problem at all, can be done many ways, cheaply, analog or digital.
We're talking about measuring chemical levels, NH3/4, NO2, NO3 etc. etc.

It would be great if you could pop down your local electronics store and pic up a 1-wire digital probe set for $5, but ya can't

That would make me so happy. I went to my only local electronics shop to pick a few more temp probes. Nada. ADC? Nope. They had 37 billion trillion resistors and a few basic 74 series IC's. Thats about it

yeah, its hard for electronics shops to keep a decent range. Buy online Farnell is great for small orders and free shipping !
Digikey is better for larger orders $30 flat rate to australia