building a ph tester

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lorenzo08

Well-Known Member
my project for this thread is to build a ph tester that connects to a computer to continuously monitor a res. if anyone has any experience or advice, please post what you know.

pH meter - Wikipedia, the free encyclopedia
The Simplest Possible pH Meter
pH meter construction

the second link looks very simple, and might be accurate with a little adjusting. only thing I'm not sure of right now, how do I make a test probe? just 2 wires or nails or something, or does one have to be copper and the other silver or something?
 
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silverstyle

Active Member
I'm thinking of tackling this soon, and if I'm successful I'll post pics.

The other things I'm planning for my small grow are:

A relay board for fans, temp, pH monitoring/adjustment, nutrient dosing and lights all controlled by a near-by PC that handles timing and graphing historical data through a simple program in loop. I pieced the design together from several online DIY sites and it should be a fun project. LED lighting for my babies was certainly an adventure!
 
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lorenzo08

Well-Known Member
silverstyle said:
I'm thinking of tackling this soon, and if I'm successful I'll post pics.

The other things I'm planning for my small grow are:

A relay board for fans, temp, pH monitoring/adjustment, nutrient dosing and lights all controlled by a near-by PC that handles timing and graphing historical data through a simple program in loop. I pieced the design together from several online DIY sites and it should be a fun project. LED lighting for my babies was certainly an adventure!
Click to expand...

interesting. sounds like you have a good idea of what you want, and a start to it. would you mind showing me your ideas? I can show you want I have too. I have my grow room wired on a serial interface card and has been running nicely for the last month. working on smarter timers and a web interface right now.
 
BigBudBalls

BigBudBalls

Well-Known Member
You are really going to have to buy a sensor. Run about $50 for a real one.

Check out Sensors, Thermocouple, PLC, Operator Interface, Data Acquisition, RTD

lorenzo08 said:
my project for this thread is to build a ph tester that connects to a computer to continuously monitor a res. if anyone has any experience or advice, please post what you know.

pH meter - Wikipedia, the free encyclopedia
The Simplest Possible pH Meter
pH meter construction

the second link looks very simple, and might be accurate with a little adjusting. only thing I'm not sure of right now, how do I make a test probe? just 2 wires or nails or something, or does one have to be copper and the other silver or something?
Click to expand...
 
L

lorenzo08

Well-Known Member
BigBudBalls said:
You are really going to have to buy a sensor. Run about $50 for a real one.

Check out Sensors, Thermocouple, PLC, Operator Interface, Data Acquisition, RTD
Click to expand...

lowest I see on there is $121. something that directly supports rs-485 would be nice. just network them all together into one com port. it's just, I'm not building a factory, and can't afford spending a grand on temperature and humidity sensors. the usb temper hum sensor is about $23 each, and would work well for the project if they were open source.
 
BigBudBalls

BigBudBalls

Well-Known Member
lorenzo08 said:
lowest I see on there is $121. something that directly supports rs-485 would be nice. just network them all together into one com port. it's just, I'm not building a factory, and can't afford spending a grand on temperature and humidity sensors. the usb temper hum sensor is about $23 each, and would work well for the project if they were open source.
Click to expand...
Look closer
ALpHA® Series Rugged Gel-Filled Electrodes

But a stand alone probe with a RS485 ain't gonna be cheap. Once you say RS485, prices jump (only because thats industrial, and they can gouge industrial prices)
 
Zen

Zen

Active Member
lorenzo08 said:
ooh nice, but those are only probes. still need a tester. I'm finding it hard to find what I need at a reasonable price, without having to build it from scratch. I'm not giving up.
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Have you gave up on this little project... I seems a great and worth project and many can benifit from... would love to see it come to completion.:hump:
 
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silverstyle

Active Member
So after much deliberation, research, and some guessing, I've decided to buy one of those gel-filled probes and use the circuit designed here:

pH Meter Circuit

I've purchased all the parts and plan to set it up tonight or tomorrow, whenever I get some time. Assuming it works, it will become part of a larger environment management system.

Lorenzo, I know you asked about more details of this, and I'm definitely open to sharing, I'm just going in so many directions at the moment and have nothing nailed down save for a few simple circuits and some basic diagrams, so I'm not sure I would be of that much help quite yet. When I finish a few of them and get them working, it will be a different story and I'd be happy to collaborate. Let me know what you think.
 
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lorenzo08

Well-Known Member
silverstyle said:
So after much deliberation, research, and some guessing, I've decided to buy one of those gel-filled probes and use the circuit designed here:

pH Meter Circuit

I've purchased all the parts and plan to set it up tonight or tomorrow, whenever I get some time. Assuming it works, it will become part of a larger environment management system.

Lorenzo, I know you asked about more details of this, and I'm definitely open to sharing, I'm just going in so many directions at the moment and have nothing nailed down save for a few simple circuits and some basic diagrams, so I'm not sure I would be of that much help quite yet. When I finish a few of them and get them working, it will be a different story and I'd be happy to collaborate. Let me know what you think.
Click to expand...

I can't wait. please let me know how it turns out. I haven't given up yet either. just working on other things at the same time too. bigbudballs sent me a link to a very nice little co2 sensor. I think you just supply it with a stable 5v regulated supply, connect the sensor output to a similar op amp circuit, then take a reading. I love it. gotta get more parts.
 
la9

la9

Well-Known Member
I'd use a ph sensor and connect it to the parallel port. That way you can write a program in Basic for what you need to do.

You need to know about electronics so you don't blow up the port.

Good Luck
 
BigBudBalls

BigBudBalls

Well-Known Member
la9 said:
I'd use a ph sensor and connect it to the parallel port. That way you can write a program in Basic for what you need to do.

You need to know about electronics so you don't blow up the port.

Good Luck
Click to expand...
FAR from a trivial project. A/D, sampling times, power, buffers, etc.
 
la9

la9

Well-Known Member
I doubt you need A/D and all that. Depends on how compicated you want to make it.

I'd use a PH probe into a comparator, 5 volts is on and 0 volts is off. Then use a relay to control everything.
 
BigBudBalls

BigBudBalls

Well-Known Member
la9 said:
I doubt you need A/D and all that. Depends on how compicated you want to make it.

I'd use a PH probe into a comparator, 5 volts is on and 0 volts is off. Then use a relay to control everything.
Click to expand...
Or how accurate/useful I wanna make it.

LOL! A pH sensor will be a high impedance analog signal.

So, a Go-NoGo gauge? Kinda useless for computer control. You would have to adjust a pot manually for the software to work.
I'm 1000 miles/km from home and want to adjust my pH .2 How am I going to do that? My arms aren't that long to tweak a pot.

Don't know about you, but I'd prefer to know *WHAT* my pH is rather then just know if its high or low and not know by how much. Kinda helps on how much corrective solution to add.

Why use a $500-100 computer (and the electricity to run it) just to turn on a solenoid from a comparator??? I'm stumped. Easier to just have the op-amp fire a the solenoid directly. (plus less room for error from an OS/Computer.)

Relay? Not concerned with a efficient/quality design, huh? MUCH better options out there. Starting with a simple JFET.

But have at the comparator (I'd prefer a window comparator) if you feel that fits your needs.
 
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lorenzo08

Well-Known Member
I guess my biggest question is still, can I make a quick and simple ph probe, or is it something that MUST be perfect and of good quality?
 
L

lorenzo08

Well-Known Member
the parallel port method works great and is simple. I've used it in the past, but I'm using a serial interface card for this project. I have 4 adc ports per card. I have 1 card in use at the moment and is running my grow room. the prototype I'm finishing up now has 2 cards in a box, so I'll have 8 adc ports to use. I'm pretty sure they are 10 bit, 0-5 volt.
 
BigBudBalls

BigBudBalls

Well-Known Member
lorenzo08 said:
I guess my biggest question is still, can I make a quick and simple ph probe, or is it something that MUST be perfect and of good quality?
Click to expand...
I don't think you are going to do it. They are, from what I've read, a glass bulb/bead with the 'stuff' inside. I think to gather all the needed items, it wold be cheaper to buy one.
Other thing to think about, they wear out. Water is kinda caustic. Especially DI. Even more so if in the solution full time.

The El Cheapo ones work on dissimilar metals and 'try' to work off that. Buy one and take it apart. They are only like $5 or so.

I was going to use the el cheapo moisture meters fed into an AD on the PLC to control watering. But found my watering schedule is fairly consistent, or I can peek over the webcam and decide for myself.
 
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lorenzo08

Well-Known Member
BigBudBalls said:
The El Cheapo ones work on dissimilar metals and 'try' to work off that. Buy one and take it apart. They are only like $5 or so.
Click to expand...
the $5 ones on ebay, I got one to try. the moisture part of it works ok, but ph testing doesn't do a thing on the meter. doesn't work. even if it did work, it doesn't seem very reliable or accurate, so not even worth that $5. I was hoping something like that tester would work well enough.

I've only seen ph probes for $60+. are they available for around $25 or so maybe?
 
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