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Forum Index : Microcontroller and PC projects : Measuring PH in MMBasic
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Bryan1 Guru  Joined: 22/02/2006 Location: AustraliaPosts: 1344 |
G'Day Guy's, I do have a few 200 litre plastic drums I want to use as a fermenter and the PH would be good to read as the ferment goes along. So doing some research found this I have bought one to have a play with now looking at Mick's RPZ modules may be the way to go as at present I only have my CMM2. Regards Bryan Edit: Now have 10 RP2040-zero's on the way Edited 2024-08-12 14:22 by Bryan1 |
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| Bryan1 Guru Joined: 22/02/2006 Location: AustraliaPosts: 1344 |
Here is one link I looked at and as it has been done already by a pi then got a head start  Ok got 5 pcb's of the RPZ compute modules and also the MB1 Compute boards on the way now for some reason JLCPCB didn't put both my orders in anyway $7 total for both boards and all should arrive around the same time so plenty of fun in a couple of weeks. Edited 2024-08-12 15:36 by Bryan1 |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 4223 |
The CMM2 can handle that also without pico. The sensor settling time is 60 seconds... you need to read it either I2C or SPI. Volhout PicomiteVGA PETSCII ROBOTS |
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| Bryan1 Guru Joined: 22/02/2006 Location: AustraliaPosts: 1344 |
Got 5 of these drums mate and once I have the first one sorted I'll have to order 4 more probe kits. Now the probe itself was $16 and with the breakout board included $32 in total so once this breakout board is looked at making one myself may be the way to go so only probes need to be purchased. So basically only temp and PH will be needed for each drum and the CMM2 can handle all the data. If I am thinking right that is  |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 4223 |
Have you got a link to the circuit diagram? And some info on how to translate electrical values to PH? Volhout PicomiteVGA PETSCII ROBOTS |
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| Gerad Regular Member  Joined: 10/01/2024 Location: GermanyPosts: 42 |
Hello Bryan I am using an ADS1115 Ic2 ADC 16Bit and OCS.tec Mini PH electrode probe for PH meters (waterproof, maintenance free, BNC connector with 1.6m cable) + Liquid PH Value Detection detect Sensor Module +DS18B20 digital stainless steel temperature sensor . I am still working on the software translation (Python to Webmite). regards Gerad |
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| zeitfest Guru Joined: 31/07/2019 Location: AustraliaPosts: 482 |
Maybe try this , I would update it to a INA116 as the comments suggest |
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| bigfix Senior Member  Joined: 20/02/2014 Location: AustriaPosts: 128 |
Quite some years ago I played with PH Meters to check my water softener output I found it very challenging to maintain the electrode longerterm and finally gave up You need to have special buffered reference solutions for PH4 and PH7 to adjust the meter display value You need to store the electrode in a storage solution, it must not dry out to long But even then it drifted a lot and needed readjustment So I believe the electronics is the simple part... Edited 2024-08-13 02:28 by bigfix |
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| Bryan1 Guru Joined: 22/02/2006 Location: AustraliaPosts: 1344 |
The more reading I'm doing on this the intriguing it's becoming it's just like the old days when I built my first metal detector where a very small change in signal was amplified to enable a microphone to beep.Now there isn't much detail on the probe side of things that actually make this work but on reading they are 2 probes where one probe allows hydrogen to pass thru which changes the small signal where the other probe completes the connection. Looking at this breakout board I'll bet they are a couple of opamps there and maybe a small micro to output the signal. So more research to be done on the probe side of things so I can understand just how these probes tick. Regards Bryan |
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| zeitfest Guru Joined: 31/07/2019 Location: AustraliaPosts: 482 |
The glass in the ph electrode can get coated with proteins biofilm etc which alters the readings - I wouldn't plan on leaving it permanently in the fermenting mix, probly best to research how the breweries do it. There are continuous-process sensors available but they cost $$$$ |
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| Bryan1 Guru Joined: 22/02/2006 Location: AustraliaPosts: 1344 |
So on reading some of the probes are coated in silver chloride where one probe is in a known PH solution while the other probe is exposed to the liquid. Now just had a look and guess what I found in my gear, some silver chloride powder in my Dad's gear called Horosilv So may just have to coat some copper wire and see if I do get a differential reading between the probes and found I did need to have both probes in the same solution. Ok coated some 2.8mm wire and put the probes in some PH4 buffer  Then some PH7 buffer  Now it did take a minute or so for the voltage to stabilize so the first rough trial is getting there. Cheers Bryan |
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| Bryan1 Guru Joined: 22/02/2006 Location: AustraliaPosts: 1344 |
Decided to make up a solution of silver chloride with 150ml of water and plate the anode which is the 2 probes. Being going an hour now and a clear coating is seen and I'm keeping the current down to around 400mA @30 volts. I did find using higher currents had the cathode fizzing pretty good. I'll repeat the coating for the next few days to see just how much silver chloride I can get onto the copper probes so a more accurate reading and hopefully a stable reading after settling in which is repeatable. All good fun in retirement |
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phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2135 |
What you are plating that electrode with is pure silver. The silver that is coming out of the solution is being replaced by copper being eaten from the other electrode. The solution will now be a mix of silver chloride and copper chloride, which may turn the solution blue or green as the amount of copper rises. |
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| Bryan1 Guru Joined: 22/02/2006 Location: AustraliaPosts: 1344 |
Yep the solution did go from green to blue so decided to clean up the probes and have another go with the 4 and 7PH buffers and got a total different reading where PH 4 was stable around 4mV and the 7PH was -10MV now looking at the mV range of a PH probe this is way off. So next trial will be rubbing on this horosilv with a damp rag to some thin brass plate as thats how it reads to apply the stuff. Then cut the probes to size and see how it goes. As I do have that silver chloride here may aswell use it and see if I can get close to what the spec's say and it is all a bit of fun. Anyway a good read about mV ranges of PH probes and the slope. Edited 2024-08-13 16:34 by Bryan1 |
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| zeitfest Guru Joined: 31/07/2019 Location: AustraliaPosts: 482 |
Are you trying to measure ph, or trying to reinvent ph meters ? |
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| Bryan1 Guru Joined: 22/02/2006 Location: AustraliaPosts: 1344 |
Just learning the down and dirty aspects about PH probes mate and eh when one has the same coating that is used well if you never have a go you will never know. On reading the set of probes MUST be separated but off my first trials today having both in the same solution does give a different reading for PH4 and 7. Got plenty of time on my hands so if this brass plate method works to the slope range then it's upto a pico to do the number crunching which is where I will need a step up as it will be needed. |
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| Bryan1 Guru Joined: 22/02/2006 Location: AustraliaPosts: 1344 |
G'Day Guy's, Well finally got some info on this PH sensor and here is the schematic for the sensor board.  Now here another pic showing the connection setup.  Just checked the tracking and it's still a week away but now got some info to work with. Regards Bryan |
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Quazee137 Guru Joined: 07/08/2016 Location: United StatesPosts: 567 |
check out Sparky's I learned a lot from his work. Quazee137 |
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| zeitfest Guru Joined: 31/07/2019 Location: AustraliaPosts: 482 |
There are standard ic's for this task eg this which is worth a read |
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| Bryan1 Guru Joined: 22/02/2006 Location: AustraliaPosts: 1344 |
Well those RP2040's turned up today and not long after had my first picomite showing up in teraterm Those PCB boards should be here any day too but now the fun can start once I find all the info on this RP2040. Regards Bryan |
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