I’ve considered doing this, but you have to be aware that typical pH probes are not suitable for this project. They aren’t rated for constant service, so you can’t keep them in the solution continuously.
That said, you can get industrial probes. They’re a little pricey and they only last a year in service.
Something like this is what you need to start with. http://evergrow.me/product/industrial-ph-probe/
Hysteresis really should be straight forward for someone familiar with embedded technologies but LOL, think on that introspective discovery a bit. You are unknowingly scratching on some hidden wounds which individuals experienced in the field tend to avoid. That would be an example trigger phrase.
This is a starting point, if it has a micro-controller involved you’ll have 50+ percent of the work that could be built upon or ported to another controller.
Also a start. A well architected system is modular. Which means you can strip features from the software that you do not need. If you can determine an open source project that is using off-the shelf DIY modules such as arduinos, Atlas shields, and so forth, you’ll have little to do beyond stripping of the un-needed features. Maybe a little bit of figuring and programming for anything unique beyond what is provided. And, of course, getting up to speed on how to use the “stuff”.
If you are doing PH, you’ll want to measure temperature as well for compensation. So, either two probes (temperature and PH) or a probe with a temperature output, too.
And, what @lefthandseeds has said. A PH probe with a constant service/immersion rating if the probe is going to remain in solution for long periods.
See Leaving the pH probe in RDWC reservoir...?
I got into a debate about that with a friend of mine. A nice argument, not a heated one. He is a fan of agile. I am not. He is developing chargers for lithium polymer batteries, and runs an agile embedded team. I tell homie that agile, modular, development only makes sense if you have realistic expectations of significant scope creep. I mean, seriously, your only job is to charge a damn battery, why bother with bullshit?
We drink about that argument often. My only job is to turn lights on and off, albeit with input from photocells and occupancy sensors, but really zero modularity is needed. Super straightforward. HC11 kinda straightforward.
I think you are right though, I got triggered and all hysteretic. 
/on Very good. Please forgive me, here comes a rant. Agile is a “cool” name but it is the bain of good engineering. Sounds great on paper only. Agile in actual practice has nothing to do with design for modularity (which has existed since the beginning of time) and it does NOT produce well designed systems. In fact, by definition, it is for developing systems where no-one really knows shit and it’s all about “constant” delivery of shit pieces until they have something pieced together that looks sort-of like a larger pile of shit. The only thing modular about it is that they produce these shit pieces with little forward looking insight (water-fall) and ever changing requirements. When on occasion something is known ahead of time, the definition of those shit pieces flow downhill by dictate.
We now have a generation of engineers that couldn’t engineer themselves out of a paper bag, in part, due to how Agile is abused by corporations. They never actually learn, through practice, how to design a good system from the start. They are not allowed to.
It doesn’t surprise me that a manager would be on-board with that, usually for all the wrong reasons. Scrum, extreme programming, etc etc. But, it’s kind-of a cool-aid thing. How do you know beer is good if all you ever have tried is cool-aid. Do you think these methodologies are actually meant to improve product engineering? Sometimes but rarely it seems, ulterior motives do lurk whether it’s used for production of complicated or simple systems… /off
I love your rants @Northern_Loki. A sane voice in the hive mind.
Have to admit, my emotional response did in fact throw the baby out with the bathwater - modular does not mean agile. My bad. But that is the context I see all day long.
Our firmware team is still holding on to good values: logic, linear algebra, and combinatorial algorithms, amen. But they are getting displaced. Our front-end guys got the boot just over a year ago…
Latest victim was our inventory management that went from a boringly stable DOS-based system to Oracle. 14 months, and still worse than doing it in excel. Modular though. And agile AF.
You wouldnt know beer is good at all. Maybe one day you would go to a bar, get shitfaced on vodka-redbulls, wake up with a hangover and say “man, booze sucks, I’m never drinking anything but cool-aid again”…
Our firmware guys are the vodka-redbull-all-night types. Its gonna be a sad day when they all retire. And that day is looming closer and closer.
LOL Yeah, Im sure phrases like “I dont think that will be all that difficult” have to rank right up there with “Hold my beer, and watch this…” I have been kicked in the butt many times after saying, or thinking, that exact thing. 
I know you mean well, and I thank you for the tips, but… Im sure those would be a great start for you or anyone who understands the programming - even a little. For me, you may as well ask me to jump over the moon before fixing breakfast.
At the moment, just thinking of doing that makes me want to take a nap and then pop some pills and take another nap.
I would like to think that I could do that stuff - eventually, but thats just not realistic any more. I just dont have the mental energy or time to put into learning the language well enough to be successful. It would take a dedicated effort over a long time period and Im just not up to that any more. I could do some stuff - if someone holds my hand. I could change variables or pre-set values to modify how program functions - IF - some told me exactly where they were and what to change. Im pretty sure I can figure out how to load a program onto an Arduino - with some review and trial and error, and I know I can assemble the various parts, provide power, and other simple stuff. But not the programing.
LOL I love you two going on about ‘agile/modular’ systems, and how the ‘new guys’ suck. Us old farts need to stick together!!
Dang. I assumed all the probes had temp sensors built in. Looks like its only the $$$ ones. So, that adds at least another $40 to the cost for a temp prob and board, plus more programming.
Well, crap. This is becomming more and more unlikely.
I am glad to hear I’m not the only one to hates the way new devs work. Been a programmer for almost 30 years now and I can’t tell you how many sprints I’ve blown up at different companies over the years…
Add me to the list of grumpy old men… 
Sorry to derail, back on topic.
No, I get it. You’ve been clear about this a number of times. I’ve composed responses but each time I end-up throwing them away because they sound like I’m being combative.
Well, here goes. The current approach to the project you are pitching produces negative incentives. Think about it this way:
Hi Joe, I’d like to built my own custom spec home in order to save money. But, I don’t want to actually have any part in building it because I don’t have the experience in building homes. I would rather oversee the construction and pick-out the appliances. I need to find some carpenters that’ll do that. This needs to be done on their off-time and without compensation. Oh, and they must be available to help my friends build their home, too. Because, you know, it’s easy and it’ll be fun for them. Oh, and could someone point out some architectural plans that they’ll modify then give to me?
Believe it or not, this kind-of thing occurs rather regularly in real life business.
Hey engineer, I have this great idea. I’ll be the CEO and you can do the work of building it. I’ll own the company and direct your work and, in return, you’ll get some stock options which will be worth bazillions (in some fantasy future). Sound good?
Pitching it in this way, personally, causes my ears to ring. Don’t take what I’ve said in the wrong way, the idea to open-source useful stuff is fantastic and laudable. But, there is likely a more equitable/sharing way to go about this. I can help with your goal but it will need to start with a thorough discussion in PM first.
It’s not really a “new” guy sucks, it’s more of a curmudgeon’s look at how these folk are setting themselves up for abuse and how the product of such machinations is generally subpar. The new guy though, who hasn’t tried the beer, is rah-rah about the cool-aid to their own detriment. They are unable to make the big picture / sound engineering connection because their pool of knowledge and experience is purposefully limited. But, they are all rah-rah because they think the manifesto of Agile software development is intended to help them in their efforts and careers as engineers.
It is not for them (in practice). They are being manipulated. FYI, agile came about around the same time frame that ethically challenged psychologists were deployed in process development in order to manipulate small groups of people. Coincidence? We now have some of the same folk who created the manifesto in the first place backing away from their own creation. Because, it’s been subverted.
The advantages of “business” centric Agile is a compliant workforce working to implement requirements and business goals that have the transparency of a velvet cloak, the ability to firewall the value creators, commoditize, demean, and devalue the engineering community, produce and release product fragments with no-say or sign-off from the engineering staff, and the ability to dictate schedules and engineering methodologies.
When things fail in the customers hands, it is often accompanied with shocked expression (after being blamed) across the engineering staff that, in many instances, weren’t even aware that a customer has received their “unfinished” and “constantly evolving” work product.
A rather public example of how this works is the VW emissions scandal. Who did they instantly blame, here.
A decent summary by this person from 2015 (it has gotten worse since then), https://michaelochurch.wordpress.com/2015/06/06/why-agile-and-especially-scrum-are-terrible/
I understand perfectly. Thats why the first sentence in this thread starts “…Im going to admit up front that this is a selfish request…”. I considered trying to re-word things to make it more palatable, or try to disguise the nature of what I was asking for. but that would make it even worse in my book.
I have been in your shoes many times. I can say with a clear conscience that I am an expert when it comes to RC flying models, and especially electric power systems. I cant count the number of times someone has approached me with a similar attitude/question - “Would you please design and build my plane for me?”.
My grandson is a perfect example. He said wanted to learn to fly models like I do. Except he didnt include the word “learn” in his request - I foolishly added that myself. When I realized what he really wanted, for me to build him a plane he could then fly and crash - and have me fix it for him - my reaction was just like yours. “If you dont want to learn the basics, and at least help build your own plane, I am not going to teach you to fly. Cant be done. You will never master it or get any good at it. You want your cake, but you want me to bake it for you.” Etc etc.
I understand perfectly because I have the same reaction when approached that way. Im sure most people are the same when asked for a wildly inequitable exchange.
I was hoping that making this a ‘community’ or open source type project, would help - at least to some degree. If several people were willing to contribute expertise to the effort, that would spread the pain around. I was also hoping someone would already be working on something close to this and be willing to share ideas, and code.
Thats still a huge and grossly un-fair thing to ask.
So, yeah. Dont feel bad for feeling like that. In this case, you’re normal and I am that ass.
I am curious about this process development manipulation - do you know if any of it got published? Or something to go on for curious minds? Ethics in psychology is a big topic. Hard to learn things about change of thought in humans without stressing them. I worked for the dept of psyc at a major university for a while, it is in fact my first degree. We went on ad infinitum about stanford and milgram studies and ethics involved vs how much we learned.
So yeah, super curious how agile can be linked to manipulation. I need some ammo for my next beer with my agile-loving friend.
Point was that it’s a hard sell to get folk that have already done this type of work by using this approach. Someone who has already has “done it” likely wouldn’t want to be constrained under someone else’s framework. Then consider all of the landmines that come with it.
I do wish you the best towards your goal. There are certain ways Open Source projects progress that make them successful. And, I have offered to help you towards your goal. But it would have to start via a PM discussion to establish the boundaries of how that would proceed.
No, I do not have anything off-hand. Mostly read, study but do not retain that kind of information. And, actually I can not recall if I’ve read published papers that are as damning as I claim other than being angry after reading certain Harvard Business School studies and “best practices”.
Much of this (agile process) started around the late 90’s or so. My main reference to my viewpoint, beyond my personal experiences, would likely have been my father, Psy.D, Ed.D. We have had in-depth discussions on these types of topics with a good deal of head shaking.
When you see how the landscape has changed over the last couple of decades and see how such methodologies are applied to business practice, it ends-up mostly tuned toward solving perceived C-Suite business problems while dropping any of the niceties. And, the engineers are huge barriers to solving their business problems.
If you’d like to open another topic, I think we should stop corrupting Larry’s thread. I’ve done enough damage. Sorry about that Larry. You can hear me bitch and moan over there 
@anon32470837, I can move these post to an alternate thread if you like. I’m pulling this off in the wrong direction.
Sorry for not responding to this earlier. I got to wrapped up in my earlier reply, and then got pulled away by real life before I could address that. I will PM you shortly.
Thanks!!
I will leave that up to you. I do not normally get up-set about off topic discussions - especially if Im curious about the subject - which I am in this case. I’d say if this thread doesnt go anywhere, then just continue as you please. If we do get going toward something concrete, then Im ok to move it - but post a link
Most nondiscreet multivariate problems have a number of solutions. Business, as a discipline, seems to be especially blind to that fact.
In order to solve a problem we must first realize there is a problem. Then we need to define what a solution to that problem might look like. Then we need a way to operationalize the variables and develop metrics that will allow us to gauge how close we are getting to a solution.
I think agile mindset says “the problem might change, and we will still be further ahead towards a solution than if we never started working on a different problem to begin with”.
Fragmentation of the team efforts I think relates to the definition of the problem. Do they know what problem they are solving? Or is it only the nontechnical or semi-technical PM who has an idea of the scope?
Engineers need to know what they are building. I would pay good money to see an agile process being applied to a design of a bridge, or an electrical distribution system in a compmicated building.
“WAIT! the bridge is now a tunnel. Make a new autocad layer!”
You two are reminding me of a research project I was hired for several years ago. A local marine engineering firm landed a contract to design/build an amphibious drone. This was back before anyone called them “drones”. They had no in-house experience with RC, or aircraft of any kind, but they got the contract because of the marine requirement.
I lucked into the job as the guy at the pointy end - actually building and flying the models. One reason I got the job because I had already designed and built several, very unusual, amphibious models. I knew, from the first time I read the project goals, that it would never work. Almost every single requirement was mutually exclusive. Aircraft are design compromises. You can go fast OR fly long distances, but not both. You can have STOL capability OR you can carry heavy loads, etc etc. They wanted a smallish, autonomous, amphibious craft that could fly long distances, with heavy loads, into and out of very tight spaces, like a small clearing in the woods, or a small river, or lake, in the hills, etc,. AND land and take off in a sea state 3 from well off shore. Sea state three is pretty rough water. That last requirement alone is almost impossible by itself, and certainly not possible carrying heavy loads, and a ton of fuel AND being STOL, and all terrain capable. Oh - it also had to be stowable in a small space on a ship, which means folding wings, and be strong enough for regular navy grunts to handle it with no damage.
Anyway, to shorten a very long story, what you two are describing sounds very much like what I went through - endless meetings, re-designs, and literally daily re-draws of the CAD files, and ‘procedures’ I was supposed to be following. There were two main engineers over seeing my part, plus three different CAD guys with another engineer over them, plus the two or three bigger bosses - all of them had to have their fingers in the pie, and none of them had a clue about aircraft design or building. I had a blast though and made darn good money doing my “hobby stuff” 8 hours a day
Oh, I built and flew several iterations on the design, but we never got to a flyable model that was actually any where near the design goals. They ran out of money long before we actually got that far. IIRC, I think the final report said that they spent less than 1% of the total funds on my part - the actual building, and flying of the models. The rest was all planning, ‘studies’, re-designs, and administrative stuff.
Talk about $10000 toilet seats
Wow, less than 1%? How do I get a job in “planning”? 
The pedestrian bridge that collapsed in Florida earlier in the year? Getting closer.
Was talking with a friend this evening who happens to be a VP of development at financial service company in Chicago. He was pretty much railing-on about the utter lack of knowledge at the upper echelons about the time and expense required to pull of IT and engineering efforts. Says they had a product bringing in $70MM in revenue and were limiting reinvestment to an entire $2MM for development, maintenance, and equipment along with a full-time staff of 7 developers (who are also on call 24/7). They can’t understand why they are having reliability and scalability issues. It should just work with a wave of the magic wand. Get moving hamsters. That’s the level of direction.
The Pentagon Wars
Do you remember a game called “lemmings”?
A friend of mine always says: “if you play stupid games, you win stupid prizes”
I have listened to an audiobook on my long drive to tuktoyaktuk this past august (forgot the title). It was by an Israeli economist who described series of experiments where they measured a person’s willingness to let go of options. I will try to get the jist across. If this does not make sense, let me know and I’ll look up the book and chapter.
They had in their computer “game” 3 doors, each door had a bunch of objects behind it. You click on an object and get paid. Every time you click inside one of the doors, the other doors get smaller, until they disappear. Unless you click on them at a monetary penalty.
Even though the best strategy would be to close all doors and keep clicking inside the one you are in already, people tend to keep doors open, get stressed, and make way less money. We have a really hard time letting go of options, no matter how detrimental.
Perhaps that is the problem- we found a methodology where the hamsters can be told to carry on in any direction. Just like in Lemmings.