Isabella has done a hellofa fine job with the EC meter project. Havent built it yet but sure it works as well as comercial units. Been thinking of doing something like this for a while and she has saved me a lot of research. It would be interesting to leave the electrodes active all the time and use a microcontroller (PIC) to log the nute concentration so as to find the optimum grow parameters.
Unfortunately her work on thePh meter wasnt finished but a cheap hand held unit will do. Seems that the ideal Ph is already known.
Anyone else interested in this ?

EC/TDS/PPM Meter

Cheepo pH Meter

interesting.................that is all

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supercalavagalisticexpialadankbitch...

Well thats encouraging LOL

I'm intestered, not much on electronic theroy, but able to solder and build, lol.
I was looking at Growtronix, but not if I could build it. Have also been looking into home automation devices and how they could be put to a "better use".
Peace

yea i found it very interesting probably never do it but still f-in cool

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supercalavagalisticexpialadankbitch...

Ok. Heres my take on it. The circuit is pretty simple- a few op amps in different basic configurations. She describes the operation. It can be built on a solderless breadboard easily. Everything is available from Digikey. The only "big ticket" item is the breadboard. Maybe 25$UDS. Components are dirt cheap these days. You often see stuff surplus. All electronics is good.
Digi-Key Corporation - USA Home Page
All Electronics Corp - Parts, Supplies and Components

It wouldnt be all that hard to log the EC readings to a microcontroller. But noe you`re into a programmer-about 100$ and good amount of dedication to learn how it works. Here is the datasheet for a simple micro(PIC).
http://ww1.microchip.com/downloads/e...Doc/41203D.pdf
Pretty intimidating eh?
Actually not that complicated once you get some basic concepts down.
Now that I think about it, it would be possible to do away with the analog components and build the whole thing in software by using the pic to generate the AC waveform and reading in the voltage with its onboard analog to digital converter (ADC)and then send the reading to a graphic display or whatever.
Now if you could somehow log the amount of water the plant consumed it might be possible to write some intelligence into the code so the nutes could be changed "on the fly" and the response noted by the PIC. It could then learn self-adjust the nute level in order to optimize growth. Now we are into a dream system fer sure- but doable.
Of course you could play with the photoperiod too.

you can get a EC meter for $40.00 why would you want to do this?????

i have an ec meter, but would like to incorporate it with a computer contolled grow, it would be eaiser to build and know what the circuit is doing then to try to modify and existing meter *imho, but the parts might come in handy!
Peace