Backyard Aquaponics
A place to discuss aquaponics

Hi All,

Just finishing up the design of my little pilot system. It's Yabbies, some 10 liter plastic tubs, coir medium, and it's configured as a CHIFT POST system (pump outside sump tank) to make life easier on me. Haven't stuck yabbies in yet as I'm still finishing up the physical works and getting stuff cycled. Had a nasty algae bloom with all of the warm weather so I'm clearing that up.

I have a large variety of microcontrollers to work with and have been knocking up some printed circuit boards (PCBs) for a custom controller. Being a scientist and engineer, my instinct is to run at this with all of the instruments I can muster. I thought I would temper my enthusiasm with your collective experience, if you'd oblige.

I'm trying to determine which sensors would be actually useful, and which would be "icing". The sensors I have considered up until now for the system are:

pump flow rate

pH

temperature (fish tank)

temp (grow medium containers)

temperature (ambient air)

solar intensity

Total Dissolved Solids

Oxygen Reduction Potential

grow medium container water level (in 10mm increments)

I know that pretty much none of these are actually required to control the system. I'm interested in hearing from those that are running sensors, which they are running, and how they feel about them. It's easier for me to design in the support for sensors and not use them than not do it and have to band-aid it in later.

If there's something you're using or would desperately want I really would like to hear about it. If there's something you've used that you thought was not worth the effort or expense I'd really like to hear about that as well.

I've already sorted out the pump control side of things, and the facility for driving solenoids with an intelligent driver solution to conserve power when on solar.

Thanks very much all for your help!

Cheers,
KS

I don't have a system up yet so I cannot comment on what I have, but...

For mine, I would like
Water temp in FT
Water level in ST
Ambient air temp

I think PH might be nice as well as sun intensity. What or why do you think you TDS and ORP? What does that affect?

John

Temp in and out and PH are very handy - i wish there was an always in water PH probe, PH is extrmemly annoying.
i would like amm. nitrite/ate. potassium. iron. magnes. Dissolved oxygen, plus a few others if they were cheap and didnt require calibration.

All i have is an inside and out thermo and an aquarium master test kit.

You mean like this Yavi?

https://www.sparkfun.com/products/10972

You might need a UV light sidestream to stop it getting clogged with bioslime though...

Ping sensors are great for level. I took 10 consecutive pings and averaged them out to allow for ripples. Worked like a charm

I have several ultrasonic rangefinders like you describe for level sensing to play around with, but also I am looking at using capacitance sensing to measure tank levels as that only involves a single electrode per tank.

I'll see if it's worth the trouble to set those up vs setting up a rangefinder.. I think one of the ones I have supports I2C as analog is gross


I would really like a pH sensor in the fish tank for datalogging and "debugging" as I go along. I have read many cases where people have observed pH swings that eventually self regulate. This would be handy to be able to log and correlate to weather conditions and feeding and plant growth etc..

Oxidation Reduction Potential is apparently very common to pay attention to in the aquarium industry, and are measured to track the activity of microbes and bacteria in a water source. There are more specific aspects of the chemistry that I won't go into but they can be used essentially in reverse to evaluate how our water health is.

Total Dissolved Solids measures the mineral content of the water.. as opposed to Total Suspended Solids these are your magnesium carbonates, bicarbonates, and other minerals present in your water. Adelaide city water is very mineral laden, leading to scale in electric kettles etc.. those are your dissolved solids. There are some studies that show that high TDS levels coupled with thermal stresses can cause dieoffs and other stresses in aquatic life.

I'm not as worried about turbidity quite yet, as gross (meaning large) particles can be dealt with using a coir mat/sand filter in my sump so I'll worry about that later.

Dissolved oxygen would be really good as you could trigger aerators at night as required instead of wasting the power if it wasn't required.

To prevent sliming, you could put the sensors in a flood compartment.. and take hourly measurements. They would have time to dry out in between, and worse case you could stick a whole handful of UV LEDs in the compartment to wreck anything that tried to grow in it. That's how I would attack that issue anyway..

Thanks all for your input. I'd like to avoid wasting my time with things if avoidable.

Cheers,
KS

Yea like that Rsevs, but without the calibration needed and one that can be left in the water like a temp sensor is.
i dont think people will come up with anything any time soon though.

I was thinking about using capacitance sensor for level as well, however the bioslime gets everywhere and i guessed it would make measuring the level near on impossible. I ended up using ultrasonic because for the cost of the units, they are easy to set up and reliable. I would be interested in seeing how you get on with them. As you mentioned you could set up a bit of pipe with some UV LED's, but i just couldnt see the few dollars saved as worth the effort.

I would be curious to know how yo plan on measuring ORP, TDS and O2 in a completely autonomous fashion...

Ummmm.... None and none....

I know, I'm different...

Yavi, that sensor only needs calibration once every 12 months and can have the tip permanently submerged for continuous reading.

It also looks like atlas scientific have a DO probe now too, which will make it much easier for hobbyists.

i might have a think about it, all of the reviews seem to be bad.

Check my sig, I've got temp and the ping sensor working. Simple math turning it into volume.

I'd love an ammonia, nitrate and nitrite sensor. But I don't know of any good ones

I've looked carefully at the atlas scientific sensors, but they don't have great reviews. From what I read, you've got to keep just the tip in the water, any more and it plays up, and for the AP setup where water level is constantly changing, it's a problem.

I'd love to see somebody buy one and give it a go though.

I cant really find many reviews on the atlas scientific stuff aside from what is on the sparkfun website. Not unusual to find a bunch of negative comments when people cannot get them working.

As for just the tip submerged, it would be a easy enough to have a section of your system constant height... It wouldnt be a bad idea to have a section that has the input flow hit with a UV light to stop any bioslime from forming on everything anyway....

That's exactly what I was thinking, have a small container/chamber that has a handful of water chemistry probes in it. A small circulation pump can fill it every hour, or you could fill it off the grow medium container feeds and then just use a solenoid to empty it when the measurements are stabilized and recorded.

Have you seen the performance of the Charge Time Measurement Unit on Microchip devices rseves3? It's pretty good, and calibration is pretty easy.. could even use a ultrasonic to "train" it.

There are lots of available (ebay) immersible sensors for the aquarium industry that do TDS, ORP and the like.. I haven't found a dissolved oxygen sensor I like.. and pH sensors grow on trees! It's just a matter of characterizing the probe or finding the OEM datasheet on it and calibrating my instrumentation amplifiers on the PCB accordingly. Keep in mind that many of these generate a small voltage based on the chemical reaction you're measuring, much like a thermocouple does with it's dissimilar metals. Knowing it's range and having an idea of any regions of non-linearity I can buffer the probe with a commonly availible instrumentation amplifier IC and then run it straight into a microcontroller. Currently I'm considering the PIC24FJ256GB110 as I have several on hand.

That would provide me with enough I/O for 25 sensors at least, and many, many more if I make as many of them digital sensors because I can run them all on a data buss.

[quote = Columnmn] I'd love an ammonia, nitrate and nitrite sensor. But I don't know of any good ones[/quote]

Yeah, that seems to be my real "Indiana Jones" task at the moment, I can't find any sensors for those ions that aren't absurdly expensive lab instruments. Where if I was doing this for a client I wouldn't have any issues, I'd bid the sensors and show them the benefits. But out of my own pocket for a pilot system it's just really not worth it at all. I really wish I could find something that would, because it's something that would make all of our lives so much easier.

I guess worst case you could "Rube Goldberg" something up with a CMUCam and a traditional test set and some peristaltic dosing pumps. Fill the container, dose the compartments of the test kit with the requisite reagents and then use a machine vision system to read the results and determine what your levels are. That's well beyond what I'm willing to do however. Just because I can determine and engineer a solution doesn't mean I want to go that far!

Thanks for everyone's feedback, it's helping me get an idea of what I'm going to start with instrument-wise.

Cheers,
KS

Don't tell porkies EB; I am almost sure you have some pretty flash meters. Of course if you wish to dispose of these I work at the tip and will pick them up and there will be no landfill charge.

Currently I log temps from the FT, GB, Sump and outside air. Added to that I also log DO with one of the Atlas Scientific probes.

I am about to log and control the water level in the sump using ultra sonics then not too far away another atlas probe for PH.

None of the above is needed but then the data logger is not needed either but it is all fun and can give interesting results.

Such as running the same system in F&D with a siphon and Constant flood, same tanks, beds, plants, water and fish. No measurable difference between them. Same as BAYP found but with two separate systems.

Just interesting.