Reef-pi & Robo-tank Salinity options

the register

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I need a secondary salinity tester. I historically used a refractometer, but after re-entering the hobby I'm using a Hanna. I recently had a snafu where my salinity went very off because my Hanna went majorly out of calibration.

I was about to go order a Milwaukee gauge to just be done with this (use the Hanna as my backup), but then I was thinking I'd rather have a constant monitor, and thought about my reef pi on my robo tank. So questions for @Ranjib and @robsworld78.

Regarding reef pi, am I correct that the salinity offerings didn't get integrated? I see threads discussing it, but don't see mentions of it in the software nor my quick code check. Regardless, do you have any recommendations on the various ways to connect a sensor?

Regarding robo tank, I think I'd have to use a USB one, because robo tank uses (at least covers) all the gpio pins. Is that accurate, or is there a way to connect an arbitrary sensor, or even specifically a salinity sensor?

What I was thinking of doing was buying an atlas salinity sensor kit, and connecting it to an ESP8322 wifi+Arduino board. That'd then mean I'd have a portable salinity gauge, in theory able to just run on a battery if I wanted. I then would pull the data from it over wifi on the pi, write it to a file, and then have reef pi read the file as an input. That seems like it'd be relatively cheap (definitely under $100), I wouldn't have to deal with figuring out how to wire it to the robo tank, and I could use it to test all sorts of things without needing to lug the pi around.

Anyway, curious if there's a well turn trodden path for this, and if not, any thoughts on my build out idea.
 
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the register

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Well, Atlas Salinity Kits are more expensive than their pH kits, so they're by itself well over 200$ :grinning-face-with-sweat:

You could of course always connect one through I2C, either a digital sensor directly by I2C, or an analog sensor through an ADS1115 or similar.
Oh geez, I actually already looked those up and I swear the links I followed from guides had them for $60. I'll have to find the exact thing I was looking at earlier. It's possible that I'd accidentally had my pH monitor tabs open.
 

Ranjib

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The ezo ph driver in reef-pi can be used to connect orp or ec sensor as well. So there should not be any issue reading those values , just use the existing ph module .
I have never used ec/salinity probe as they are expensive, require more tuning and I never felt it’s required . A good functioning ato generally solves this (salinity ) and a cheaper specific gravity meter is way more robust I felt, for my use case

but while I don’t use , I would love reef-pi users to be able to use and experiment with salinity probes if they want . Let me know if there’s any the blocking you from doing this with reef-pi.
 

robsworld78

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Oh geez, I actually already looked those up and I swear the links I followed from guides had them for $60. I'll have to find the exact thing I was looking at earlier. It's possible that I'd accidentally had my pH monitor tabs open.
The circuit is $68 (was $60) but then you need the isolator which is $28 - $32. You could get a probe and calibration solution elsewhere.

If you get the I2C isolator you can connect that to the external I2C port on main controller. If you plan to only use one circuit from Atlas you could get their USB isolator, personally I like this better as I2C is best left on circuit boards and not run through cables. I emailed Atlas once to ask if more than one USB isolator could be plugged in as Pi has 4 USB ports but they never responded so to be safe I say only one can be connected.

To work with reef-pi you should be able to read it using the pH tab as @Ranjib mentioned as all Atlas circuits use the same command to send out data however what I'm unsure about and maybe @Ranjib knows, what happens with the EC circuit as it can output 4 parameters, conductivity, TDS, salinity and specific gravity for sea water? Will it parse out the first piece of data and discard the rest? I worry it could throw a parse error. Do you think calibration will work from reef-pi? @the register if it doesn't you can still calibrate using the same Atlas script though the SSH terminal.

Actual Circuit

I2C isolator

USB isolator (looks like they only have gen1 version in stock)
 
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Wolfw28

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Could reef- pi/robo-tank read a usd probe something like this? Or figure out how this probe works.
 

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Sral

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Could reef- pi/robo-tank read a usd probe something like this? Or figure out how this probe works.
It's certainly possible, but probably quite a bit of work to figure out the Bluetooth communication between the device and the APP.
I'm just not sure if it's worth the effort, since you would probably have to sink several hours into this (equaling several dozen, if not 100s of $ worth in time). So as long as we don't find somebody who does if for free because it is fun for him, I'm not sure that is a viable way.

I'm going to try to build something myself, as explained here. Those circuits work analog, so they give a voltage proportional to the electrical conductivity. You will therefore need a ADC module connected via I2C.
I have also linked two other DIY builds there, one uses more current and one does less. Less current is obviously preferable in a tank with Fish, but it is more prone to errors imho. If it works I can maybe convince @robsworld78 to make a board similar to his pH sensor and sell that, but that would take quite some time ^^
 

robsworld78

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Could reef- pi/robo-tank read a usd probe something like this? Or figure out how this probe works.
As @Sral mentioned, anything is possible, sorry but it's above my pay grade.

It's certainly possible, but probably quite a bit of work to figure out the Bluetooth communication between the device and the APP.
I'm just not sure if it's worth the effort, since you would probably have to sink several hours into this (equaling several dozen, if not 100s of $ worth in time). So as long as we don't find somebody who does if for free because it is fun for him, I'm not sure that is a viable way.

I'm going to try to build something myself, as explained here. Those circuits work analog, so they give a voltage proportional to the electrical conductivity. You will therefore need a ADC module connected via I2C.
I have also linked two other DIY builds there, one uses more current and one does less. Less current is obviously preferable in a tank with Fish, but it is more prone to errors imho. If it works I can maybe convince @robsworld78 to make a board similar to his pH sensor and sell that, but that would take quite some time ^^
If you come up with something I would be happy to get some made, actually someone else is working on one as well, I don't want to say who but if he see's this maybe you guys can swap notes.
 
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