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Discussion Starter #1
LF: Affordable ammonia/nitrite/nitrate & NPK sensors. Want to fully automate my tank.

Does anyone know of anywhere I can find affordable chemical sensors? I'd love to fully automate my tank eventually and I'm thinking of starting with a monitoring system. I have seen a few different systems that exists for this but none of them have sensors for the nitrate cycle incorporated. It is possible that these types of sensors are just too expensive or don't exist commercially, but I thought I would put some feelers out and see if anyone knows anything.

I have sources for pH and temp, but if anyone knows about KH and GH, I'd love to hear about that too :)
 

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Indeed. There are nitrate probes on the market; but they fall into my definition of 'crazy expensive' (in the several hunded dollar range for cheap ones). Your millage may very though. However, keeping track of ammonia or nitrite in a truely digital fashion is really crazy expensive. For ammonia though you can probably do something like the Seneye guys and use a colour sensor pointed at a chemical patch (I've considered trying this with a Seamchem ammonia alert patch... but in my tanks I'm not too concerned about ammonia). I have no idea about the PK part of NPK either. It's not normally done anyway.

As for GH and KH, the best you can probably do without another foray into very expensive would be a conductivity probe.

So are you going DIY with this or are you looking for a ready made system? I'm currently testing my arduino based system (Internet enabled! Data available here... if you like looking at long lists of numbers); which at the moment just has temp and pH. For pH I'm using the board made by This guy with an el cheapo pH probe from ebay; which is working well after I escaped from grounding hell (the very low voltage signal generated by glass electrodes is suscpetible to interference from the induced voltages in the water produced by nearby lights, motors, etc... needs to be isolated or grounded in some way).

For my system, I'd ideally have temp, pH, ORP and conductivity (and possibly some extras like water depth or filter flow rate). I feel like that would be enough to keep tabs on any changes that might happen (dunno about automation though... that's currently out of the scope of the project. Aside from light controllers or dosing pumps; which I feel are difficult to mess up). I'd also like to get a better brain. The arduino's great for getting stuff going quickly and easily... but I'd really like to write code for a controller where you aren't sweating every byte (also, something like a raspberry pi is much cheaper for what you get vs arduino these days... although it's not quite the same market).
 

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Discussion Starter #4
DIY for sure. I hadn't thought much about the controller yet, I was thinking of the Arduino or Raspberry Pi, but also considering something by Freescale Semi - I have used some of their stuff at school and liked it a lot... they are pretty expensive though.

Um... "affordable" to me is $100 or less per sensor. I'm going to be putting it together piece-wise to keep immediate costs down... Probably going to start with the simple and cheap - pH, temp, water level/flow from filter.
 

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Awesome. Haven't ever run into Freescale before (but then I'm an environmental science/geology grad... so that's not suprising; what program did you do?). The arduino platform is nice and easy (The essential hardware is all there. There are lots of tutorials and examples floating around. Plus people have made shields for just about everything); but the atmel chips are not super powerful. I'm using the older model based on the ATmega168. I'm extremely limited on memory space. Once I've added in the ethernet stuff I've just barely got room to calculate and send the pH and temperature data to the cloud (and I had to be careful about how I handled my strings in order to do it at that). Of course if I upgraded to a 328 I'd be able to do a lot more stuff (like add my LCD screen back in... I have to check the web page for data even if I'm standing in front of the aquarium :( ). One could also go with one of the big boys; but the price tag goes up quite a bit.

I've been looking at the raspberry pi as well. The brain is slightly more expensive (about $10); and that doesn't include other stuff you'd probably need (like an ADC, SD card, etc). On the other hand it's a full up linux system; so there's all sorts of good stuff you can do with it (log data, send email, issue commands over ssh, generate pretty graphs in real time, interface with a normal USB wifi card), all without buying an extra shield (which can be quite expensive... wifi shields are between 40 and 90 bucks vs a $10 'good enough' usb adaptor) or worrying about storage space. However, it lacks the ease of the arduino ecosystem (althouth there is decent documentaion for the pi out there now).

But yeah... sensors. The ph sensor I linked to is the cheapest I've seen. You also need some calibration solutions (I got mine from the local hydroponics store... the nice thing about BC is we have huge numbers of hydroponics enthusiasts ;) ). Waterproofed digital temp sensors are available for very little via ebay as well; although they don't tell you the material they're made of (I've seen people coat their probes in food safe heat shrink though). For mine I hacked off the end of one of those (uselessly cheap) digital aquarium thermometers I had lying around; which just so happened to be a 10K thermistor. Ditto for flow sensors; although I am once again slightly nervous about the type of plastic (although these guys have one with a listing of materials... they are, however, based in China; so there's that). (Atlas Scientific makes a bunch of sensor packages for hobbiests that interface via serial (particularly nice for the ADC-less pi); but are somewhat overpriced to my (very cheap) mind (also they're based in the states and their shipping to Canada is a bit pricey). They are nice sensors though.

There are a bunch of different ways to do depth. Float switches, ultrasonic sensors, fancy etape things and bubblers are all possibilities. Personally I like bubblers at the moment (uses a pressure sensor and an airline... probably the cheapest, most reliable setup with reasonable accuracy over a full tank depth. Haven't built it yet though; so I don't actually know).
 

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Discussion Starter #6
I'm working on finishing my last year of Mechatronics engineering at sfu. I was thinking of going with a float sensor for water level, and also keeping one inside my filter to ensure it doesnt overflow or something. I figured it would be easy to DIY that with some sort of strain gauge... might buy one though, I can think of how I would DIY it, but the logistics of waterproofing it are awkward and things never go quite as they should...
 

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I'm working on finishing my last year of Mechatronics engineering at sfu.
Nice. So really I should be asking you questions then :). I'm moderately up on the chemistry side of things; but I'm mostly making up the hardware side as I go (I took a few courses in electronics back in the day... but I've forgotten most of it).

I was thinking of going with a float sensor for water level, and also keeping one inside my filter to ensure it doesnt overflow or something. I figured it would be easy to DIY that with some sort of strain gauge... might buy one though, I can think of how I would DIY it, but the logistics of waterproofing it are awkward and things never go quite as they should...
Lemme know how that goes. I'd like to see what you come up with. I like the bubbler idea mainly because it requires little in the way of mechanical/waterproofing stuff (might be kind of a buzzkill for you though). I figure I should be able to do it with one of these and an airline.

I've been researching "Aquamonitor 2.0" a bit lately (acutally, I found a Nanaimo-based parts store. Which I am super stoked about). One thing I'd highly recommend is isolating the more sensitive probes (pH, etc) because the electrical noise in the aquarium. My first pH data looked a bit like this.

why me?.jpg

I did eventually work around the problem (put a grounding probe in right next to the sensor and made sure my equipment was plugged in in a way that minimizes ground loops); but it's kind of kludgy. Of course if I done something like this (which I found the other day) I wouldn't have had that problem. My current idea for a dream system would be to make a board with pH, OPP, conductivity all hooked up to an isolated serial ADC (ideally 12+ bits. The 10 bit ardunio ADC is slightly lacking in resolution... it plays into the precision/accuracy of the sensor a little bit).
 

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That is actually pretty cool. Hasn't been released yet though... should be interesting to see how it goes.

Seems kind of similar to the seneye (which I'm not super impressed with). I like the idea; but implementation is everything. Sometimes making things consumer-friendly ruins the magic a bit.
 
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