PH control

[wilsonjholmes]

Yes. Atlas sells female bnc breakout boards that make it easy to connect bnc probes to the circuit with a breadboard.

[harrison]

Very good – I have just designed a custom PCB to fit this to Chi.Bio, will have them manufactured and keep you posted!

[wilsonjholmes]

Awesome! My university now has probes on hand and some of those atlas circuits on order. Will the code for this be on a separate branch initially in the GitHub repo? Eager to test and help.

[wilsonjholmes]

When will the pH control add-on boards be available for purchase?

[harrison]

I have designed the PCBs and have some (unassembled) sitting on my desk, but have not had time to assemble them. If you fancy doing some soldering I can send you schematics so you can do it right away.

[wilsonjholmes]

I am comfortable with soldering and I would love to get my hands on stuff. Where could I get a look at the bill of materials and the schematics?

[harrison]

Sure – What file format can you use? Do you have access to any PCB software? If you do not have editing software I can send you Gerbers that you can use to get it fabricated and a BOM.

[wilsonjholmes]

I do not currently, but I have used KiCad and Eagle in the past, I have access to both through my university.

• This reply was modified 4 years, 1 month ago by wilsonjholmes.

[wilsonjholmes]

Sorry that last reply was contradictory. 🙂 I *do* have access to PCB software. Either Eagle or KiCad should work.

[harrison]

Sure, I have emailed you the draft schematics and PCB files, let me know how you get on.

[danda]

Hey Folks! Curious on the status of pH control. Is there any pH control available for purchase? If not, can you share the schematics and PCB files? Thx!

• This reply was modified 2 years, 5 months ago by danda.
• This reply was modified 2 years, 5 months ago by danda.

[robl]

Hey hey,

I am also wondering how the pH can be measured in the ChiBio.
I do not have an implementation, but I read this paper: https://link.springer.com/article/10.1007/s00449-015-1409-4
They used LED signals to measure the pH. Depending on the angle of the LED response, the pH can be estimated.

In the recorded data from the ChiBio I do not see any information on the angle. I am not familiar with sensors that measure light. Would it be possible to measure also the angle and therefore the pH in the ChiBio?

[harrison]

Hey Rob,
So far we have not implemented this broadly. Mostly people have either sampled the output waste or installed very thin PH probes into the lid. Or, some pH responsive dye that they put in their media and then measure colour change of.

For that paper – they are using phase angle of response to see fluorescence lifetime. I.e. it is not the physical angle of light incidence, but a proxy measurement for how long the emission delay is which one can measure with a high frequency modulation of the input LED. At present Chi.Bio would not be able to do this since the photodiode spectrometer wouldn’t allow fast (and synchronised) actuation and measurment (I think it at least needs to be in Khz range https://link.springer.com/chapter/10.1007/978-3-642-56853-4_13). So no, this is not possible. The LED might just be able to support that level of control given it can change PWM frequency, but even then it would be a square wave with some delay and messiness which would make it very tricky even if the right optical sensor was implemented.

[SilasV]

Hi,

I would be interested in using an ORP sensor in place of a pH sensor. Would this be possible? Atlas seems to sell equivalent ORP sensors and chips to the pH sensors and chips mentioned above.

[harrison]

Hi Silas,
Seems it would be if you had connected up the Atlas PH Sensor the ORP would be much the same, assumign you can get a probe that effectively fits into a (custom) lid of your design.

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