Real Time Application

Norml · Nov 3, 2006

Hi all. I have an application involving high tides where I must enable a duplex pumping station to pump 1 hour before to 1 hour after high tide (sheesh). I have a 2Mb .csv file showing the date and time of each high tide for the next 30 years. Hardware = CompactLogix/PanelView. I don't have a clue as to how to approach the real time portion of the program. My first guess would be to use the real time clock function (RTC) and somehow compare it to the .csv data. If someone knows of a way to do this, I would certainly appreciate a kick in the right direction. Thanks,

Norm

Tom Jenkins · Nov 3, 2006

This sounds like an application for a basic co-processor. You should be able to copy the CSV file to the co-processor, have it use the PLC clock registers to look up the data, and have it write a pump on and off command to the PLC processor.

SimonGoldsworthy · Nov 3, 2006

30 years is approx 20000 tides so you could store the start/stop times in a look-up table indexed by the number of days from the start point. You certainly don't need to store the 2M of data. I don't know what the memory capacity of a CompactLogix is, so this may or may not be a kick in the right direction.
By the way, what is the PanelView for ?

Norml · Nov 3, 2006

Hi Tom,
Thanks for your reply. Sounds like the cat's meow but I don't see a co-processor available for the CompactLogix system. Are you referring to a 3rd party product?

TimWilborne · Nov 3, 2006

If it is 20,000 tides then it shouldn't take but around 160K to store the date and time of all of the tides. Should be able to store them in the Compactlogix with no problems.

Tom's probably got some trick up his sleve with the coprocessor through, let's wait and see

Norml · Nov 3, 2006

Hello Simon,

I'll look into setting up a look-up table as an option. Sounds interesting as long as it remains in sync with day one without having a date field available. Don't know if the spreadsheet can by downloaded - or I'll have to hire someone for data entry since there are nearly 22,000 entries.

The PanelView is for displaying and enabling alarms, selecting lead/lag and alternation pump sequences, displaying and changing wetwell on/off control and alarm levels etc. All this for a small outdoor pump control panel in the middle of nowhere with radio telemetry to a SCADA system.

Thanks for your response,

Norm

TimWilborne · Nov 3, 2006

22,000 tides with time and date would be 176K

Norml · Nov 3, 2006

Hmmmm.....we're getting warm here. The 1769-L35E has 1.5Mb of user memory. Sounds do-able especially if there is a way to feed the PLC data without manual data entry.

ndzied1 · Nov 3, 2006

Just saw an ad for an "IN-RACK PC" for control logix from Prosoft. Don't know nothing about it but it might make the developemnt easy. http://www.prosoft-technology.com/content/view/full/1062They also have BASIC modules. I have never used them but I'm sure people here have.

Good Luck

Norml · Nov 3, 2006

hey norm!

Just checked your link and they have some interesting stuff. Infortunately it's for the ControlLogix system. There doesn't appear to be much out there for the CompactLogix platform. Thanks
Norm

Steve Bailey · Nov 3, 2006

The fact that a table of times of high and low tides exists at all indicates that there is a formula available to calculate those times. I have no idea how complicated that formula is, but it seems to me that an approach worth considering would be to duplicate that formula in the CompactLogix processor and calculate the times.

SimonGoldsworthy · Nov 3, 2006

In Siemens Step 7, you can create data blocks as text and compile them into blocks that are then loadable into the plc - is that an option here ?

colerick · Nov 3, 2006

How accurate does that one hour need to be. Seems if you could accept 5 or 10 minutes of error, you could greatly decrease the size of your table.

???

Andy

Paul T · Nov 3, 2006

radio telemetry to a SCADA system

Is this one way only? If it's two-way, then you can (a) store the tide tables for the next century on the HMI and (b) have the HMI download something like 30 days ahead to the PLC on a daily basis, so that the PLC can live without connecting for a while.

Aside from that, I agree with Steve Bailey. And even if the formula isn't viable for some reason, when do the tide tables repeat? Can you store, say, 4 years worth of data and call up the correct slice each year for the next 30 years?

Norml · Nov 3, 2006

Hi Steve,

Good thinking on replicating the formula for internal calculation. Unfortunately, the formula is fairly complex and uses a minimum of 15 variables for calculation. I think the required data would be far larger than the resultant calculation. The people at JTides did a great job in creating a Java program to output tide charts in Excel for nearly anywhere in the world.

Real Time Application

Norml

Member

Tom Jenkins

Lifetime Supporting Member

SimonGoldsworthy

Member

Norml

Member

TimWilborne

Lifetime Supporting Member

Norml

Member

TimWilborne

Lifetime Supporting Member

Norml

Member

ndzied1

Lifetime Supporting Member

Norml

Member

Steve Bailey

Lifetime Supporting Member + Moderator

SimonGoldsworthy

Member

colerick

Member

Paul T

Member

Norml

Member

Similar Topics