DIY Tank Monitor --> Tank Controller chat

Hi, well i've tried to search for it, and he mentioned the Vernier amp for it. I am also trying to figure out the conductivity and ORP electrodes, since they behave differently then PH. I also read the entire thread on reefcentral, but i didn't get any wiser there.

All i've learned is that you use sensors from sensorex, which you've bought from Ebay. Unfortunately, i can't find anything on Ebay right now. I get the point that you would like to have a 4-20mA range for PH 0-14. What i don't get is how you'd get e.g. 6.85 PH reading out of that.. So that is my first question; how you've sold that with which components and so on.

Secondly for both the conductivity and ORP; they give a 0-1000mv range. Which 1-wire component would i use for that?

I'll have a look, however thought the reef forum had a ph amplifier for US$60.00 ?

Anyhow the ph meter I have is a foxboro 872ph...they are on ebay however need to find them being sold for ~40.00 each...I paid US25.00 each for both my PH and ORP meters.

4-20ma output is actually 1-5VDC if you place a 250 ohms resister in series with the output. Thus you usually power the device with 24VDC and place a 250 resister in series, then just tap off 1-5VDC into a1wire chip.

There are other 1wire voltage input devices that do go 0-10VDC.

http://owfs.org/index.php?page=voltage-measurement

pH amplifier http://www.vernier.com/probes/ea-bta.html shipping is US35.00 cheaper for two ! ie 1 for ph one for orp

Quote:

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Originally Posted by Bad Inferno

4-20ma output is actually 1-5VDC if you place a 250 ohms resister in series with the output. Thus you usually power the device with 24VDC and place a 250 resister in series, then just tap off 1-5VDC into a1wire chip.

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Meaning i have to power the Foxboro 872 chip with 24VDC, place a 250 resister in series and it outputs 1-5VDC? Sorry i am only good in software, i have someone else doing the electro ;)

Quote:

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Originally Posted by Bad Inferno

pH amplifier http://www.vernier.com/probes/ea-bta.html shipping is US35.00 cheaper for two ! ie 1 for ph one for orp

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Yeah, i allready asked for a quote. For 3 items i have to pay 180$ 3, meaning 40 euro's each.

there could be cheaper chinese units...although I did not think US50.00 each equated to 40 euros. and its was US45 to ship two units to australia

The foxboro units actually run on 120 VAC and it powers its outputs so you just put the resister across its output terminals and that converst it to 1-5VDC. Its not worth spending 100's of dollars for 1 unit.

why not try DIYJunkie ph circuit. I am sure he will share his cct and give you some tips.

I've pm'd him, but he aint responding :) Think he is busy ;)

Conductivity... As far as i have understand and read, conductivity electrodes require a voltage to be sent through the electrode? What sollution did you end up with?

Gilles,

It is very difficult to DIY conductivity measurement...The utilisation for conductivity once installed is marginal.

Its good to see how the any Med's and fert effcet the water however suggest pH and temperature to be the main things to monitor for.

My background is "instrumentation" and as such I went crazy with measurements and if dissolved O2 was not so expensive I'd install one of those just for the heck of it !

rob

Haha GOOD news! I finally got my aquaputer online and i did my first temperature readings.

However, i have some questions maybe BAD_INFERNO can answer;
a) I need a mounting script. Right now i have used the commando "/opt/owfs/bin/owfs /dev/ttyS0 /var/tmp/1-wire" to mount it, but i would like to do this on startup.
b) It seems that when i do a "cat /var/tmp/1-wire/..." the temperature is not updated realtime, does this change with owread?

Thanx

Gilles

Hi BI,

Well, I bit the bullet today and bought a NSLU-2.

I have bought it because I am going to venture down the road of a setup like yours (with other features too!) but I'm also about to do a course in Linux so there going to go hand-in-hand together.

My first trick is going to be re-flashing the device with Linux. It seems pretty straight forward but wish me luck!

Oh and one small question, what size HDD are you using on yours?

Cheers,
Col.

I had an old 10 gb 2.5" laptop drive...hanging of my SLUG. With a small drive you can power it from the NSLU2 USB port...larger 3.5" drives will need the external power adapter. Good luck if I can be of any help just PM me on the software side, its been a while however I may just be a ble to remember. If I had known you where in the market I would of given you one of my NSLU2 for a good price as I actually have two spares, now I've moved onto a small Ubuntu server.


keep us updated
rob

one last thing...there is a command that tells you what speed the SLUG is running at (I think the new one are already fatser 255mhz)... check it out and if required you can remove one resister and improve the slugs performance by quite a few %