How do I cature Temps Time and dates on PLC

[Kenariel]

Hello Everyone I'm new to the site and I look forward to sharing and learning from everyone. I am trying to figure out how to cature Temprature, time and dates for an oven that we are installing at work. I would really appreciate some feedback. On a scale of 1 to 10 my PLC skills are 6.5 but I am working to get to 10. Thanks

 

[itsmoked]

For starters your PLC will need an Analog Input.

Got one?

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[danw2]

PLCs are great for logic control and can handle analog inputs for alarming, on/off or even PID control, but with the exception of only several very recently introduced PLC models, most do not log data. Logging data is the task of an HMI.

Temperatures, times and dates are exactly what "recorders" have logged for 60 odd years in the industrial world.
Most are now LCD touch screens instead of rolled paper, but recorders display exact readings at precise times.

If you've got an HMI with some form of historian (data logger) then you can record or log temperatures from thermocouples or RTDs (presuming you have the requisite analog input hardware) on your PLC's HMI.

If it's a one shot deal, like an initial furnace survey, you might consider renting a recorder or having the survey done for you. If you're going to control the oven with the PLC, then investing in an HMI with data storage is probably worthwhile.

Dan

 

[richs]

Hiya-

Some of the "higher end" plcs have Real Time Clocks and
many have conditioned analog inputs. An instrumentation
amp (specifically designed for the thermocouple, or
other temp. sensing device) can be easily done.

Data logging typically is NOT the realm of PLCs, however
many of them can transmit data to other machinery.

Specifically, a low cost or cast off PC. You can use
RS232, RS485 (better), ethernet, or other "funny"
interfaces.

Data logging can be easily done as well as statistical
reports via several logging programs. For me, I use
'nix boxen and RRD for data logging. This is an offshoot
of the old MRTG program that's been out for quite a while.

You can find it at:

http://oss.oetiker.ch/rrdtool/

I've used it in commerical systems. 'nix (specifically
linux) is a viable, low cost operating environment with
enough robustness to allow one to sleep at night. Uptimes
for me run at least 100s of days and oft times much longer
as I would do something stupid like pull the plug, or
some stupid admin goof. I would not sleep well at nights
if I had to rely on a Windoze system.

Alternatively, a PLC with a little SBC system. I use
another SBC hardware stack (I need the PC104 interface),
but something like gumstix:

http://www.gumstix.org/

is a low cost solution. This could use the flash memory
card to download the RRD information. Typically they
are little ARM processors, running uClinux. If memory
serves me right, they run around $140.00 US with the
ethernet about another $40.00 or so. I could be wrong
on the prices. Alternatively, the gumstix has an I2C
interface which could, in theory, be "easily" connected
to some of the PIC microcontrollers.

Of course you can use a pic and a compact flash and run
them all from the PIC, but that's quite a bit of programming
effort and unless you want to make a product out of it,
there would not likely be a return on investment. And there
are, as mentioned before, other products out there already.

I use a little square SBC with a standard IDE disk interface
(again with the PC104). The hard disk allows for much
more data to be stored and can be used as the swap device
so that standard Linux can be used. The SBCs that I use
cost about $400.00. They most likely would be overkill
for a new application, so I will not dwell on this further.
Except to say that if I didn't use the SBC that I do, I
would certianly look at the gumstix. I might order one
anyway, but not right now.

Best of luck. Hope that this helps.

Cheers,

Rich S.