Wifi Sensor System

[techno_gardener]

Hey everyone, I've been working on some aquaponics automation and am looking for feedback on what people are most interested in. The system currently monitors pH, dissolved oxygen, water temperature, and air temperature. It sends data to the cloud and displays it on a dashboard with live graphs: https://portals.exosite.com/views/3102634191/2406506743. It can also control pumps, lights, and vent openers for greenhouses. The next version will also monitor ammonia and nitrate. Is the control of the pumps and lights, or the monitoring of the sensors more important to you? I am not sure what features are most valuable, and would appreciate any advice on what the most important features for this kind of system are.

[Jason]

How far along are in testing the unit? One thing I tend to like is when all the sensors are combined so that we do not have to have multople cables when one will do. Oh, and it would also need to at least water resistant, if not water tight. Are you planning on mass producing the units?

Jason

[techno_gardener]

We've been running two of the systems for 3 months now with pretty stable results. I can see the water tight requirement being important. Right now we're just making some prototype systems so no plans for mass production but mainly trying to get more runtime on the prototype systems. I can also look into making a cable assembly to combine the probes together.

[David - WI]

Neptune makes a big deal about "galvanic isolation" to get reliable, realistic measurements... how are you addressing that?

[techno_gardener]

The majority of the circuit is not isolated as it connects to the power supply that's plugged into the wall. This includes the wifi chip which does all the sensor readings and sends the data to the cloud. To keep the sensors isolated the power coming in from the power supply goes through an isolated DC-DC converter to power the sensor circuitry. The communication going between the wifi chip and the sensor circuitry is also passed through digital isolators. If any electrical noise from pumps messes with the sensors you'll usually see erratic readings. So far the two systems running in the actual aquaponics systems have had stable readings so the isolation appears to be working.

Right now I'm working on the nitrate and ammonia sensors. Does anyone have a preference for which one is more important to monitor?

[David - WI]

For me it would be nitrate... but I have not seen any sensors that can be left in the water for under about $1500.

[techno_gardener]

Depending on what type of electrode you use the readings can drift quickly and the electrode can wear down over time. I'm sourcing solid state nitrate and ammonium electrodes from a manufacturer that are showing good consistency. The main issue is how often it needs to be calibrated and that depends on the accuracy you are looking for. They also have replaceable cartridges so the entire sensor wouldn't need to be replaced when it wears down. The electrodes are pretty affordable as they are the half cell type where they'll go for 400. I've been looking into this for aquariums as well and it seems like for that application people aren't as willing to calibrate on a regular basis. Would calibrations every two weeks be too much of a hassle? The frequency of calibration may be different than that depending on what type of accuracy you are looking for though.

[David - WI]

I guess it would depend what calibrating it would involve. I would need 5 or 6 or them, so if it takes less than 10 minutes to calibrate each one; I could live with it. And then cost for 5 or 6 sensore cartridges.

[techno_gardener]

For best results it's good to do a 2 point calibration. The nitrate sensor would need to go into a 1 mg/L solution, you'd wait 1 minute and then press the calibrate nitrate 1 mg/L button in an app. You'd repeat for nitrate 100 mg/L, ammonium 1 mg/L, and ammonium 100 mg/L. Right now I have an android app that does all the calibrations when on the same wifi network. Attached is a screenshot of the app.

I still don't have definition on cartridge lifetime and cost but am working on getting that information.

[David - WI]

Right now I have an android app that does all the calibrations when on the same wifi network.

That's very cool!