Grow room automation...Whatcha think???

[minds_I]

Hello all,

Sygh, I agree with you on the probe.... using a continuous use industrial process probe offer the stability and reliability that DIY can't offer. However the signal conditioning is another matter that can be dealt with either DIY or of the shelf.

As stand alone controllers...its been a number of years since I was involved in process control but my desire to use a computer is remote control application.

As to which softwaqre to use...the choices are many as you say but if you now how to write code in one language you can write in another rather quickly (with the exception of assembly). I myself have an old version of quickbasic with a compiler...suits my needs- or at least it did.

But the choices of componats are many as well. Cost, effectiveness and reliability are all coupled in the quality of the system.

Your links are great information, keep it coming.


minds_I

 

[Guest]

I'm currently using ADI's ocelot and modules, a Labjack U12 and picaxe's for I/O.
http://www.appdig.com/adicon_new/index.htm
http://www.labjack.com/results.php?category=0

The Ocelot is a nice system, but the I/O modules are a bit expensive at about $100 apiece. I have 4 I/O modules plus the Ocelot. The Labjack is also nice, but this version is USB. The net-iom is very interesting. Like the Labjack but ethernet. Around $170 US. http://www.audon.co.uk/netiom.html

Seriously, check out misterhouse. http://misterhouse.sourceforge.net/
I use homeseer, but I think they've grown too fast. Almost every beta breaks something that used to work. I have too much time and money invested to switch now. misterhouse it's probably not as flexible as homeseer, but it's free and open source. I've purchased the upgrade to homeseer, but am waiting for the 2.XX version to become more stable before installing.

I also ran across some replacement conductivity probes. They're just a cable w/ an subminiature audio plug on one end, and the galvanic probes on the other. $7 apiece. At that price it's not worth fabricating probes.
http://www.spectrapure.com/St_quality_p2.htm
They DID send the wrong items initially. However, once informed they sent the probes and a RMA posthaste.

I'm currently working on an ultrasonic aeroponic system using the cheap under $30 foggers. In conjunction w/ that, I'm working on a fog sensor/controller using a Sharp IR distance sensor. For anyone interested, the thread can be viewed here. http://www.gardenscure.com/420/aero...r-controlled-ultrasonic-vertical-cabinet.html
Nice people, but not a lot of technical expertise there. Lots of views, but very little participation. I was hoping to pick up some new ideas.

 

[minds_I]

Hello all,

Sygh, I like the labjack modules....right down the lines of what I had in mind.

Excellent find on the EC probes. The probe output is likely a voltage differential... if so, that should not be a problem to interface hopefully with minimal conditioning.

The boards from hobby boards look just fine for such a project.

In one of the links above there was a DIY solid state relay design that is just what I had in mind. Although I have been reading on using a circuit that isolates the system from the relay using optical relays???? Any info on this would be good.

Most of the systems componants have been linked are readily available. You have found free control software....this could be a doable garage project.



minds_I

 

[Guest]

Definitely doable. I don't have any good links for SSRs. I normally periodically search Ebay for "buy now" SSRs in the price range I want to pay. I prefer paying around $5 apiece, but they're popular items. I'll pay as much as $10 if I need one right now. If you're referring to opto-isolators (optical relays), yes you can homebrew a SSR from discrete components, but if you can find $5-10 SSRs I don't think it's worth the effort.

A big part of the effort is planning for component failures. Designing small subsystems and having spares on hand is important. A major problem I have had w/ the ADI stuff is that a major electrical event often times wipes out the tranceiver chips for every unit. Fortunately, it doesn't happen often, but a major PITA when it occurs. Plan for failure. Almost everything breaks eventually. The plan is to eventually convert the subsystems to Picaxe based controls.

 

[The Dopest]

 

[Grownz]

http://www.gardenscure.com/420/hydroponics/74169-computer-automated-hydroponics.html

 

[Guest]

The post I made yesterday seems to have gone into limbo. One more time. The $7 probes are electrodes only. An excitation and sensing circuit are needed. Excitation HAS to be AC w/ a 50% duty cycle to work properly. The EC circuit from the emesystems site is simple and elegant. CMOS 555s have an operating mode the old standard 555s didn't have. Operation at 50% duty cycles is no longer a chore. You can go to your local Radio Shack and buy all the components needed for less than $10.

In the schematic diagrammed, the EC electrodes and the fluid being measured become part of the frequency determining components. Output is a variable frequency or analog voltage. Very nicely done. Long term stability is very good. I've used one well over a year w/o having to readjust the cal. It can be assembled on perfboard in under an hour.

The hobby boards moisture meter is the same circuit coupled to a 1 wire battery monitor. Reads temperature and voltage. For $27 assembled, it's hardly worth the time and effort to build one. The unmodified moisture meter will only measure down to about 500 ppm, cf .7 using a standard probe. In normal operation it's not a problem as the control range is usually about 600-1300. If a wider range is desired, either the component values have to be tweaked or a probe w/ a larger surface area needs to be used. I have an Excel sheet I used to curve fit the data, but I can't attach files yet.

 

[Ono Nadagin]

You post some very interesting info Sygh.. ty

hmm a cmos 555 timer? who knew... how long have these been on the market..

I hate to say it, but I have not kept up with IC developements since I got out of University.

And I have to admit that you obviously have a firmer grasp on it thn I do as I understand completely how changing the values of the components on the board would allow you to change the control range of the meter, but I am totally lost as to how changing the size of the probes surface area would do the samething... if you have the time or the inclination to explain it to me, please do.

 

[Guest]

hmm a cmos 555 timer? who knew... how long have these been on the market..

I have no idea. I've been out of the electronic/process control business for about 10 years now. I ran across the lmc555 on the emesystems site a little over a year ago. That's when I discovered that the CMOS version had a simplified method of generating 50% duty cycles. The older version didn't have the same mode of operation. Link to a PDF, scroll down to the 50% duty cycle oscillator. http://ssdl.stanford.edu/classes/AA236/2005A/documents/aa236/LM555 Specs.pdf

, but I am totally lost as to how changing the size of the probes surface area would do the samething... if you have the time or the inclination to explain it to me, please do.

I usually use water flow as an analogy. Not 100% accurate, but close enough. Voltage is the equivalent of water pressure. Current is the same as volumetric flow. If the pressure (voltage) is kept constant, but the pipe diameter increases the volumetric flow increases, even though the linear flow rate stays the same. That's w/ discounting non laminar flow. Or, take two resistors of the same value. The resistance to flow is the same for both resistors. Put them in parallel, and the flow of electrons is doubled, even though the resistance to flow hasn't changed. By increasing the physical area of the electrodes, the linear flow rate is still the same, but the volume of electrons per unit time doubles.

The hobby board moisture meter uses surface mount components, so changing components is a PITA w/o suitable equipment. But as long as the useful range is in the range of interest, not a big deal. Otherwise, it's better to build your own. My first meter was scratch built, and I used a basic Stamp to read the data and transmit it back to the rest of the system. The Basic Stamps are a bit pricey at $50 a shot though. The picaxes are neat little devices, but w/ some limitations. Picaxes are just PIC processors w/ an embedded interpreter. No hardware UART/USART, and the internal timer is shared. Things like serial i/o aren't quite as easy as w/ a device w/ hardware serial buffering. But, the price differential makes them attractive. The 1-wire devices make intercommunication/networking pretty easy. Some of the i2c devices look to be useful also. There are some serial i2c 10 bit (or larger) ADCs that are in the under $10 range.

 

[Ono Nadagin]

Thanks Sygh I get the idea now, ty for taking the time to explain it to me... I just had my head stuck on the notion that I have seen tiny probes to giant probes that all had the same measurment range and didnt think it though enough.

 

[Ono Nadagin]

I thought you guys might be interested in reasing this post
http://www.icmag.com/ic/showthread.php?t=44334&highlight=microcontroller

It is the closest to a member has gotten to doing what I want to do... he like Sygh, is a bit sharper than I... but it is an interesting read and something I am messin around with myself ... cept I am toying with a Paralloax Propeller chip http://www.parallax.com/propeller/index.asp

It will be a long time if ever till I get it all figured out

 

[Guest]

There are some good things to be said about a central controller, and an old tired PC has more than enough power to do any/all of the tasks associated w/ growing. However there's a big scramble when the control breaks. I personally like the concept of distributed processing. When something breaks I only lose some functionality. It doesn't shut the entire operation down. I can usually operate in limp mode for a few days, or I can delegate control of that function to another device temporarily. But, there's more than one way to skin a cat.

Pic microcontrollers are probably the most bang for the buck. They can be bought in small quantities for less than $2 per. They are limited devices, but are more than enough to perform a single function. A lot of people prefer the power of the Atmel devices, but IMO they're overkill for this type of stuff. I burned out on assembly in the late 70's to mid 80. Intel, Motorola, MoS Technology, RCA.. So I'm really not interested in learning yet another architecture or another assembly language. It all becomes a waste of time in the end, unless you just like that kind of stuff. That's were the picaxe shines for me. Cheap, a BASIC derived language (although you always have to learn the differences), and enough power to get the job done. I can afford to stockpile a hand full each of several different models. My personal favorite was the Motorola 68HC11/12 and Forth. But still overkill.

I use the automation software (homeseer) to largely perform an oversight function. Although it does do some control, it's there more to let me know when a parameter goes out of limits. It does fun stuff too, screens calls, switches cameras when motion sensors trip (lets me know the dog is ready to come in), controls the entertainment system etc. etc. The methodology is an extension of the concepts used when programming in Forth. Small, easy to troubleshoot modules and reusable code. Individual controls are generalized hardware, specific I/O and functions.

 

[Guest]

This thread didn't die already yet, did it?

 

[Ono Nadagin]

heh no I have been spending the last few days tinkerin with stuff... you gave at least me a lot to think about.... I will be ditchin the Propeller IC ... luckily it was free, I have a buddy that teaches at ITT and they get a ton of the stuff given to them for free....

I am waiting on a picaxe from him now as well as a few labs for his students where they build anec,temp and humidity sensors and alarms..

 

[minds_I]

Hello all,

I started this thread because I thought I could be of some help and maybe cobble together a prototype that is effect and inexpensive with off the shelf parts.

After some others posted here with far more knowledge on automation with regard to equipment that I became overwhelmed. I have been semi-retired for about 15 years now and clearly I am behind the times with regard to available equipment.

So, while I might not have had anything recently to contribute, I am still reading the posts.


Keep it going, maybe something practical will materialize from all this.

minds_I

 

[BlindDate]

DA boards and associated probes, thermocouples, peri-pumps, etc are cheap and easy to come by. The key to all this is SOFTWARE. A good easy to use program would be worth a fortune in his business. A packaged set with an excellent program is what we need.

btw...Windshield washer pumps are cheap but will not stand up to pumping acid or base. Don't waste your time.

 

[minds_I]

Hello all,

Yeah, the washer pumps were just a stab. A paristalic pump is ideal and easily and cheaply available.

I agree the software is key... but not difficult to program considering the system variables. All descrite sampling and analysis loops. Nothing is coupled.

Maybe I am not seeing the trees fromt eh forest but it seems to me that the selection of equipment and some programming this is pretty much plug and play (very loosely phrased).

I am still excited by the prospects.

minds_I

 

[minds_I]

Hello all,

Sygh, I was doing some reading on the picaxe chips, specifically about some of the product line are thermally unstable...do not know if the system would be suseptable temperature differentials that my be incountered.

I like the serial port communications abilities as well.

But i am still thinking a dedicated DAU would be more down the lines of a central control system.

My reasoning is just this... the DAU carsd are designed for I/O and communitcation with the I/O ports are already established. So my thinking is rather then have individual ciruits to preform a speciifc functions autonimously they would be under the control of the PC. It seems that main issue I can see from my brief read is communications with the PC. Code will have to be written to use the serial ports for communication and the problem compounds when you have multiple picaxe subsystems daisychained.

I don't have enough experience with picaxe microcontrollers but really the use of them is really just building the DAU from scratch...could be costly in R/D.

In addition, DAU's have some robustness and circuit safety features built in. A nice plus.

I was thinking also because they are cheap ($100-$200) and software written to utilize is what I was thinking.

Surely the picaxe deices are way kewl though... if we only had them in the mid 80's, man the things that could have been done in automated control systems.

If I ramble it is only because I smoke to much dope.

minds_I

 

[LazyDaze]

I realize they go into a higher price range than you guys are discussing, but does anyone have experience with Phidgets?

For me, these seem ideal. I don't know electronics past house wiring, but these are daisychainable USB, and provide an easy java interface (as well as several others). I can do C++ (I'm a passable programmer), but Java is much easier and quicker for me (and I'm very comfortable with it), and would do just fine. If they don't have a sensor you want, they have one that measures voltage, so you can adapt your own pretty easy. And their relays will switch 250 V, so I'm covered. Haven't bought any yet.

And that's why I'm asking to see if anyone here has used them.

 

[Guest]

To begin. What i'm envisioning is a collaborative effort. A kind of open source control system. Code and hardware design to be freely shared. I'd like to see something evolve someone w/ no experience could use w/o too much difficulty. If there's enough interest, group buys could be organized to kit components. There are resources available to prototype small quantities for not a lot of money. Defining useful/desired subsystems is probably the first step.

Sygh, I was doing some reading on the picaxe chips, specifically about some of the product line are thermally unstable...do not know if the system would be suseptable temperature differentials that my be incountered.

YVery true. The largest source of error seems to be the resonator used in the lower end Picaxes. It's going to largely affect timing functions. However, w/ a bit of planning, I don't see it as a major problem. For one the environment should be relatively stable temperature wise, assuming the environment will have some controls. Secondly, I don't see the need for laboratory standards as far as accuracy. Repeatability is more important, and cal routines can be set in software. Plus specific component selection will depend on the application.

But i am still thinking a dedicated DAU would be more down the lines of a central control system.

My reasoning is just this... the DAU carsd are designed for I/O and communitcation with the I/O ports are already established. So my thinking is rather then have individual ciruits to preform a speciifc functions autonimously they would be under the control of the PC. It seems that main issue I can see from my brief read is communications with the PC. Code will have to be written to use the serial ports for communication and the problem compounds when you have multiple picaxe subsystems daisychained.

I agree that for an individual, using surplus DAUs or programmable controllers is probably the easiest thing to do. However, from the point of view of a collaborative effort, I think its better to use specific components that are easy to source. After reading through the picaxe forums, the easiest way to implement communications w/ multiple picaxes seems to be by paralleling the com pins then using a microcontroller w/ an embedded UART/USART to control information flow to a PC. Unfortunately they didn't include a timeout parameter the the serin command. The concept is that each picaxe based control has an address/id and a predefined set of commands and responses. The microcontroller responsible for communications sets a "listen" line active, which causes the slave controllers to wait for a command string. The slave controllers respond to their own address, then executes the command. It should be possible to use a picaxe as the com controller, as the only thing it has to do is to relay serial data. While the price of surplus commercial equipment is relatively cheap, the picaxe still is much cheaper, and easier to source.

I don't have enough experience with picaxe microcontrollers but really the use of them is really just building the DAU from scratch...could be costly in R/D.

In addition, DAU's have some robustness and circuit safety features built in. A nice plus.

R&D will certainly be the big expense. Labor almost always grossly exceeds the cost of hardware. Keeping the functional units small and specific will speed development time. I don't really see the development of software for most functions being excessively complicated. In fact, I believe the development of most devices will be relatively trivial and straight forward. I'm sure there will be exceptions though.

For the most part, I don't think circuit safety features are that relevant for this type of application. Provided the input and output devices are spec'ed properly, functional operational oversight would be provided by the central PC. Obviously something will break eventually, and monitoring for correct operation should be sufficient to catch malfunctions. Although it doesn't seem to be necessary, it's possible to utilize tandem controls in critical areas. The picaxe-08M is cheap enough at $3 to do quite a bit. W/ only 8 pins, the 08M is definitely limited, but they're fine if you only need a couple of inputs and a couple of outputs. There are quite a few functional processes that don't require more than a single input and a single output.

Also, we're looking at what should be a relatively stable environment, well within what commercial quality components can handle.

I was thinking also because they are cheap ($100-$200) and software written to utilize is what I was thinking.

Surely the picaxe deices are way kewl though... if we only had them in the mid 80's, man the things that could have been done in automated control systems.

You're definitely right. The resources available today, compared to what was available in the late '70s and '80s is amazing. I was transitioning from development to maintenance when microchip first came out w/ the pics. A very large amount of functionality in a small cheap package. The picaxes went a step further by making it unnecessary to learn yet another architecture and language. I think the biggest advantages of the picaxes are, ease of use and the price. The chore of low level I/O is taken care of for the most part, and anyone can lean BASIC.