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G'day all,

Working on a project, figure I should talk to the pro's before I get over my head... No not an EET or anything - I can kinda follow datasheets but - lets just say I spend a lot of time asking stupid questions of google  ;D

However, for the 3rd time - I find myself building the pH op amp circuit, and adding port expanders for an LCD and keypad... Decided - perhaps this is a sign; if I've built this circuit for aquarium controllers; and now i'm doing the exact same circuits for a hydroponics project... It's time for it to be combined into a shield format... I know a lot of hydroponics and fish types who aren't going to breadboard a circuit - but will put it to use if it's close enough to 'plug and play'. This means a shield is needed...

Wanted to make the initial circuit out of dip components - easier for home builds/testing; hopefully get someone working on some software  8-) Second version after this one gets built and some viability - want to go with smt parts - eliminate the 12v power source; and make things nicer...

Schematic can be found at:
http://picasaweb.google.com/lh/photo/hIVc5cdJPBKA53UgSa4CVw?feat=directlink

Any suggestions/advice/revisions needed - let me know smiley Yes still gotta make it fit into/onto a shield package, but the basics are there...
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Could you also provide kicad design or help with that arduinoshield.zip you mensioned in another thread?
Thanks in advance.

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Not sure what you're asking here...

There's not much to help with for that one - register for the kicad users group and download it, then import it as a component (just little more than a pin layout - make sure you've got your pinheaders in your schematic layout)
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OK. Found it..
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Back onto the growshield topic... Brought up today - perhaps adding a 12vdc fan control (think pc fans) is needed - easy enough to add a modified version of the motor control shield into this shield design... Then you'd have speed controlled 12vdc fans; already have the 12vdc on the board anyway (for the pH circuit). Thinking of dropping the direction control (save digital i/o's - jumper can control direction, as once you've got it initially setup you're probably not going to be changing it).
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4-wire pc fan is easily controlled from pwm pin. None of the shields required. Such fan has an internal transistor to accept PWM signal.
Would that work as an option?
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Maybe I'm out of the loop (quite possible, haven't built a pc in 10 years, laptops come pre-assembled); but last I bought them, pc fans typically were simple 2 wire dc motors (ok little less simple as most are brushless; but essentially add 12vdc to them and they spin up; pwm to reduce speed).
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Quote
Maybe I'm out of the loop (quite possible, haven't built a pc in 10 years, laptops come pre-assembled); but last I bought them, pc fans typically were simple 2 wire dc motors (ok little less simple as most are brushless; but essentially add 12vdc to them and they spin up; pwm to reduce speed).

The modern fans commonly have 4 wires.  2 for power, and 2 for speed.

Here's some general info.
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I'm working on a shield that caters to the aquarium and indoor growing communities too.
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1258412419

If you're interested, maybe we can put our heads together and create a full package.  I have a lot of experience driving fans as well.  Between your Ph shield, my power LED shield and maybe some others, we could make for a complete setup?  What other things need to be controlled?  Pumps?  Air?  Temperature?

The fans used in computers have a number of possible uses for the extra wires.  These are the most common:

o PWM speed control input.  Usually handles any voltage between about .7V and V+
o Standard or open collector tachometer output.  Usually 4 state changes per revolution
o Rotor lock/min speed alarm output.  Changes state if the fan stops spinning or spins too slow

A 4-wire fan usually has the PWM and OC Tach on the two extra wires.  That is the most common configuration I've seen.  Rotor lock and min speed alarm is used in web servers and such.  Standard tach is not very common anymore because the OC tach is way more flexible.
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What about elevensies? Luncheon? Afternoon tea? Dinner? Supper?

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I'd be game - you've started where I haven't - though not quite how I was planning to go; but we could always team up...

Got a TDS/EC/PPM & ORP shield on the go in kicad right now; and another shield mostly designed adding a d/a converter for 8 float switches... (Just a basic circuit - but running out of analog inputs, and 2 wire float switches are much cheaper than the 3 wire versions...)
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