Who built their own PLC based controller?

Jacob D

Jacob D

New member
I'm getting started on a PLC project and remember seeing someone's thread (I thought here in MARS) where they built a PLC controller. Anyone know who that was?
 
Steve, yours was the one I was thinking about :)

I was going to use an Automation Direct DL06. I worked with some of their stuff and it's decent stuff despite the scary-low price tag. A freind had a couple of Allen Bradley's for me though (for free) so I'm going to use one of them instead. One was a Micrologix 1600, it's the smaller of the 2, I forget what model the other is.

What I was curious about is how you handled your probes (did you do anything other than temp?). I need temp, ph, and conductivity. I'm scratching my head trying to figure out how to interface these with the analog inputs.
 
uhhh heheh I gave up on calibrating my own temp probe and just got one that's made to go with any PLC, its a 4-20 temp probe.
And I never tackeled the PH or ORP.
If I need these in the future bad enough I may tackle the interface, but for now I'm temp only.

Don't know how cheap the DL06 is but the basic LOGO unit I use is like $100 bucks, and I thought that was DIRT cheap.
And INSANELY easy to program!
 
The DL06 is $199 with 20 in / 16 out expandable to 100 I/O, and 14k of memory. The DL05 is the smaller one for $99 and has half of the on board I/O. These guys also make a sweet little 3 1/2" touch screen that connects with an RJ45 for $189. The remote screen I got for the AB is not as nice, and not a touch screen :( (but free!)

I got the AB for free and it has an analog card so I couldn't pass on it, I also have access to RSLogix, so that cinched the deal.


That sounds like the way to go for temp. I was thinking about doing the same, unfortunately I don't know of affordable ph or cond. transmitters.
 
Just noticed this thread, but I am also working on my own controller and emailed steve on the same question a few weeks back now. I'm using the cheaper approach - programming an AVR micro and building some custom PCB around it. It's not done yet, but the prototype seems to be working with only a few minor glitches.

I had the same question about PH and ORP though - and the trick as I see it is finding a cheap one I could tear into and figure out. I just could not find much on the net about how to integrate with one. If you find anything, please let me know - as I'm totally interested in doing the exact same thing.

Thanks,
Josh
 
Have either of you guys contacted any of the controller (or probe) manufacturers to see if they'll give you specifications on the probes? Knowing what they're using for input/output signal will be key to hacking some sort of hardware "handshake" to get a 4-20 output (or whatever you're after).
 
I haven't contacted any of them with that question.
I figured it would be trade secret or something for their equipment. Like I said since I just don't have a use for these numbers yet on my tank I really don't have any drive to figure it out. :(
I'm drivin by the need / necessity for all my projects..
If you guys figure it out I'd like to know too. Or, if I develop a need and end up solving it I'll let you all know how it's done too :)
 
Gresham has a controller that has those inputs, IIRC. Maybe you can pick his brain, or the guy who built if for him. I had the thread around here somewhere, but can't find it at the moment.

I was wanting to build my own, what with my electrical background (Licensed Electrician for over a decade, 5 of those wiring up commercial PLCs) and computer and programming background (I make a living now doing Systems Management for a large firm), not to mention my penchant for DIY and designing solutions for our reef tank. But I never could get the project off of the ground. While the PLC path offers much more flexibility and expandability over, say an AC Jr, I can get the Jr for less money that will do 90% of what I want out of the box. That extra 10% is a tough sell for the amount of $$ difference it would end up being (at least for the units and components that I had looked at).

If I ever get the chance to partner with someone who had access to source the part at a better price point, then I might consider it, but until that time I think I will leave the DIY controllers to you all :).
 
Hi Tom.

For most automation needs I think a prebuilt controller is the way to go. They're more compact, and maybe even or slightly less cost than a DIY (depending on which one ya price out).

In my case I'm setting up a fully automated water change, top off, and 2-part dosing system (along with everything else that needs to be controlled). I have 11 level sensors to make this work, and to give me the level of automation that I wanted. I think there are only a few controllers that would have been able to handle the I/O and more "involved" programming that I'm after, and they are the more expensive controllers. Flexibility was my main driving factor, then price.

Regarding the probes, I'll give Gresham a shout and see what he says, I'm going to be working with a Controls Engineer later today and will pick his brain too :)
 
One other option would maybe me to pick up an Aquatronica probe "module". They have one each for PH, Temp and Orp (and maybe even salinity). Just a suggestion if Gresh doesn't have the answer for ya :)
 
or you can use Parallax BASIC stamp, very easy to program, already have built in code for I/O like DAC or PWM, some of them even have I2C port built in already, which may come in handy. going full AVR micro or other microcontroller may be a bit headache if you are just using it to monitor couple probes or couple pumps, just my $.02
 
Yeah the BSII might work well for analog but since it's output is all TTL is makes it very expesnive to interface with 120V stuff quick.
 
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Dude looks like your's is a way better find than mine! (Price depending though)

Let us know what that thing costs, I might be interested in one like that.
 
Ok pricing is in... better sit down.

PH/ORP:
$536

COND:
$821


I figured they wouldn't be cheap. Those prices are with a 25% discount as well since I have accounts with both companies who rep them.


back to the drawing board...
 
ouch...Well, we know that they can be done on the cheap.. look at all of the lower priced controllers that have one or both of those built in. So don't give up hope :)
 
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