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Robo-Tank Isolated PH Circuit
Just an FYI:
There are biological processes in the aquarium that could affect PH without affecting the CO2 level, same goes for additives which can alter PH without affecting CO2.
So be sure to state clearly that it is Just a (refference) calculation which doesn’t give an exact CO2 level and isn’t therefore reliable.
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Yeah I was aware but your right maybe it should be more clear that the number doesn't hold much weight, I will add a warning where you set the kH to calculate CO2.
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Would it be possible to connect my RTC to the I2C buffer so the controller works more reliable?
You fitted the I2C buffer in order to prevent an overflow on the I2C bus if I recall correctly.
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I hope the controller hasn't been freezing on you, that's what the I2C buffer solved. But yeah if your RTC has wires attached and plugged into controller board you can move it to the output of the buffer (USB side). Make sure you only connect RTC to 5v if you use the buffer, don't use the power pin on the buffer as it's 12v and will fry the RTC. You can get power from the controller and use SCL/SDA from the buffer output.
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Hey Rob, is there room inside of the controller case to mount this internally and keep the second USB port free for other accessories?

Second, do you recommend (either for or against) mounting the pH circuit internally?

Finally, assuming mounting this inside the controller is a viable option do you recommend powering it with the 3.3v headers, or the 5v headers?

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Hi jlysaght3, I'm neutral on where to mount it, basically what fits your setup best. I've tested the circuit around other electronics and they don't interfere. I always assumed adding an extension cable would have negative effects as the signal from the probe would degrade before getting to the circuit but my probe has maybe 15 ft of cable and I've attached a 25ft extension which had no effect on the reading so yeah setup didn't have much to do with anything.

I think you have the thinner case so there isn't a lot of room but it should fit in line with the RTC battery as the circuit is about the same height as the mini w5100. Maybe place a piece of box board between the pH circuit and controller board so there's no chance it shorts out with the solder joints on controller. The spare SCL/SDA pins next to the w5100 are on the output side of the buffer giving them 5v so connect the pH to 5v power on controller.
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Hey Rob,

So I decided to mount the pH circuit inside of the slim case for the Robo-Tank. I chose to pull the board out of the case and mount the circuit underneath the board when viewed from the bottom (between the main shell of the case and the circuit board, as opposed to between the board and the cover/bottom of the case).

I soldered wires directly to the jumper pins on the circuit, and then to the main board in the controller giving me a total of <6inches (15mm) cord length between the controller and the circuit. The added benefit is that the pH probe connection is on the side of the controller facing my tank, and I keep both USB ports for accessories open for power bars and other add-ons.

I also did this so that when you have an EC board and DO board (electrical conductivity + dissolved oxygen) I can also add them into the controller case and have everything fit with shortest cables + seamless integration.

I have included pictures for reference. I think that the controller case can easily support 2 circuits behind the board, and possibly another 1-2 on top of the board for a total of 3-4 (this would account for a pH, DO, EC, and possibly an ORP all native in the case, each with full isolation + easy access connections).

PS: Filling in the recessed Robo-Tank logo makes the controller look really cool!

Attached Files Image(s)
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Cool I like pictures. I always thought the case would look good with the name colored and wow it really pops. One day I have to get a 2nd extruder for my printer so I can print it a different color.

I like where you mounted it, better than where I was thinking. Can't wait to see you have 2 or 3 more BNC's sticking out. ;)

Oh I hope you have a way to get a USB cable to program the controller, wouldn't want to unplug all those wires too often as they can break off where they clamp down in the plugs.
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I've got the USB cables covered. My desktop computer sits beside my aquarium (on the adjacent wall) and I have a pair of USB extension cables set up specifically for programming. The only thing that is a challenge is programming the display because I have it screwed to the hood plate over my tank (so any updates that require modifying the files on the SD card require me to unscrew the screws that hold that in place).

I have also thought about other placements for the controller (on top of my hood plate, mounted inside/under the stand, etc.) but am having difficulty committing to changing it because of how convenient it is to get to now and the built-in drip loops that result from this mounting configuration (especially on a saltwater system).

I'll post up some more pictures at some point :)
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Oh no, I just put out an update with some images. ;) How about trying one of those SD card extensions? I know someone who has and in the past I used them in the controller, they were ribbon type but I think they have cable as well. I think you can get them a 2-3 feet long if that makes things easier. I like how you have the controller mounted, quite a few people do it that way. It's also nice and clean with the wires disappearing.
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