Ph reading interference from AI Prime power supply

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Paulo Hanashiro

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Hello to everyone.

I got an awkward behaviour in my setup that I’d like to discuss:

Since last week, I’m getting inconsistent ph readings (ph fluctuations from 7s to 8a within a few seconds) I tried everything in the reef-Pi side (replace RPi boards, re-install everything, re-calibrate probe, have the electronics inside a metal box) all resulting in the very same instability.

Then I moved to my tank to investigate potential interference and I found that this issue happens only when I have the AI Prime powered on. I’ve tried a different power supply for the AI with the very same result. I also tried a few different power supplies for the reef-pi which improved the reading but did not fixed the issue (using an iPhone charger reduced the variation to around 0.5 ph)

In summary, the only way to get an steady ph reading is to either have the AI removed from power or to have the reef-pi connected to a power bank.

Would you guys have any suggestions to help me fix this issue?

Thanks in advance.
Paulo
 
Nutramar Foods
Thanks Saltyreef.
I believe the interference is going in the power line as I had the AI power supply removed from the tank and placed far from reef-pi, just sharing the same power outlet, and issue persists. The combination that works at the moment is using the iPhone charger in the Pi and plugging the AI in a power plug in the opposite side of the living room.
 
Top Shelf Aquatics
Does surge protected plug not filter it? Just a thought. Maybe a ups can do similar filtering for you.
it is disappointing that AI has such a bad quality power supply.
 
Sounds like electromagnetic interference. Is reef pi diy stuff? If you could wrap around it in a copper tape that is soldered or attatched to the grounds it might help.
 
Thanks everyone for the inputs.

I am now 100% sure the interference is coming thru the power line, look at the screen output,
All equipment in the very same place as before, only change is on the Pi power source.

Initially I had the Pi running in a 5v USB iPhone adapter, when I moved it to a 5v power bank you can see the line is almost perfect.

I tried a surge protected plug and could not notice significant improvement.

I guess I'll have to look into other options for a filtered/isolated 5V power supply?

Really lost here as I'm quite sure where the source of the problem is but unable to visualise a clear way out.

Screen Shot 2021-06-08 at 5.46.12 pm.png
 
ReefBot Lab, Automated Water Tester
Do you have other 5v adapters? Phone chargers, especially ones optimized for specific phones have weird electronics inside, don't necessarily always provide clean 5v

As for ups, you'll have to specifically look into the datasheets, the lower (cheaper) grades don't do any filtering either
 
Last edited:
I think I found a compromise I can live with.

I spent some time in my garage grabbing all the spare power supplies I could find.

I got an adapter from a really old guitar pedal effect (It should be filtered otherwise the power line noise would go thru the AMP).

I connected it to a 5V converter and this reduced the PH variance to around 0.02.

As a last shot, I'll try to add some capacitors and maybe an inductor to the output of this power supply to see if I can kill this interference, otherwise I'm comfortable with what I got at the moment.

Thanks everyone for the ideas.
Paulo
 

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Top Shelf Aquatics
Ive had this same issue, mine came from shoddy power supplies to led lights. Grounding and shielding did nothing because the switching power supplies were putting interference back thru the ac mains. Anything else plugged in was affected....my pi ph reading would go crazy, and other elecrtonics plugged into the same circuit.
My fix was to repower my lights with a good meanwell supply.
 
Yup, same issue with a led power supply causing the issues. I have pinpoint ph monitors that went crazy when the LEDs were on the dimming cycle.
 
Bigtrout said:
Ive had this same issue, mine came from shoddy power supplies to led lights. Grounding and shielding did nothing because the switching power supplies were putting interference back thru the ac mains. Anything else plugged in was affected....my pi ph reading would go crazy, and other elecrtonics plugged into the same circuit.
My fix was to repower my lights with a good meanwell supply.
Click to expand...
Good idea. I ordered a voltage isolator that should arrive in a few days. If the isolation does not fix it, I'll order a nice Meanwell PS with enough power for all my AI products (Prime and Nero).
 
Ecoscape Reef Rock
Is this still an issue? I am curious if a grounding probe will help
 
Hi Ranjib.

Yes, issue is still happening.

I've installed an analog signal isolator which reduced the noise but it is still noticeable.

The only way to get smooth readings is to either power the reef-pi from an isolated power bank with no connection at all with the AC mains or to disconnect the AI Prime power supply.

I've also tried some sort of shielding (Get reef-pi case wrapped in aluminium foil with the foil connected to DC ground), but it didn't make any difference.
 

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