Re: [foxboro] Simple Timer/Counter
- From: "Badura, Tom" <tbadura@xxxxxxxxxx>
- To: <foxboro@xxxxxxxxxxxxx>
- Date: Fri, 26 Feb 2010 08:36:50 -0600
Venu,
The timing for this sequence can easily be created in a CALC or even
LOGIC block using the DON function. We use similar timing logic to
provide variable duty cycle (on/off) for tank agitators. This is a
simple "latching" function and can be expanded upon as needed.
'; * Timed Cycle Control *
'IN BI02 ; Valve 2 Open
'DON M02 ; Valve 2 Time
'NOT ;
'IN BI01 ; Valve 1 Open
'DON M01 ; Valve 1 Time
'OR BO02 ; Valve 2 Output
'AND 2 ; & /Valve 2 Time
'OUT BO02 ; := Valve 2 Output
'NOT ;
'OUT BO01 ; Valve 1 Output
You may also want to provide some Process Interlocking to the actual
physical device outputs. That is, use other lower level logic to
prevent turning on either valves physical output until the other valve
is closed. If you use GDEV blocks for the actual valve device control
you can provide feedback from this process interlocking through the
DSR_RB input. If both valves are on the same FBM and you use ladder
logic this works well for process interlocking with feedback to the
DSR_RB via an OFL. Otherwise this same logic could be done in a another
(or even the same) LOGIC or CALC block.
Tom Badura
Plastics Engineering Company
tbadura@xxxxxxxxxx
-----Original Message-----
Hi there
wanted to ask you all an easy one, I want to open valve 1 for
30 minutes and make sure that valve 2 is closed during that time and
close valve 1 after 30 minutes and open back valve 2 and hold it for 30
minutes and the process repeats , its interlocking + timing . please
share your thoughts .
Thanks
Venu
-----Original Message-----
From: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx]
On Behalf Of QUEIROLO OLIVERA, IGNACIO ESTEBAN
Sent: Thursday, February 25, 2010 10:19 AM
To: foxboro@xxxxxxxxxxxxx
Subject: Re: [foxboro] Simple Timer/Counter
David,
To handle the cross midnight I would add some lines to your code:
-CALCA code snippet-
STEP01 = IN BI01 ;VALVE TOLD TO OPEN
STEP02 = OSP ;
STEP03 = BIF 10 ;
STEP04 = NOP ;IF WE ARE HERE WE JUST GOT A
STEP05 = NOP ;START REQUEST
STEP06 = TIM ;GET SECONDS SINCE MIDNIGHT
STEP07 = STM M01 ;STORE IT
STEP08 = GTO 50
STEP09 =
STEP10 = IN BI02 ;VALVE MADE LIMIT
STEP11 = OSP ;
STEP12 = BIF 50 ;
STEP13 = NOP ;IF WE ARE HERE WE JUST MADE THE
STEP14 = NOP ;OPEN LIMIT
STEP15 = TIM ;GET CURRENT TIME (SECS > MIDNIGH
STEP16 = STM M02 ;STORE IT
STEP17 = LAC M01 ;START TIME
STEP18 = SUB M02 ;
STEP19 = BIN 22 ;
STEP20 = OUT RO01;TIME TO OPEN
STEP21 = GTO 50 ;
STEP22 = LAC M03 ;86400 (SECONDS IN ONE DAY)
STEP23 = SUB M01 ;
STEP24 = ADD M02 ;
STEP25 = OUT RO01;
-ACCUM params to modify-
MEAS C:B1.P -the valve open command boolean should be 1 when
we want to time-
MTRFAC 0.5 -based on the BPC and the blocks period and phase-
CLEAR C:B1.P -the valve open command boolean transition to 1
will clear the previous time-
HOLD C:B2.P -the valve limit, a 1 will hold the value.
M03 86400 -seconds in one day
What do you think?
Regards,
Ignacio
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_______________________________________________________________________
This mailing list is neither sponsored nor endorsed by Invensys Process
Systems (formerly The Foxboro Company). Use the info you obtain here at
your own risks. Read http://www.thecassandraproject.org/disclaimer.html
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to subscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=join
to unsubscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=leave
_______________________________________________________________________
This mailing list is neither sponsored nor endorsed by Invensys Process
Systems (formerly The Foxboro Company). Use the info you obtain here at
your own risks. Read http://www.thecassandraproject.org/disclaimer.html
foxboro mailing list: //www.freelists.org/list/foxboro
to subscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=join
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