Internet PLC Forum

HI,

I really appreciate the help but either I'm completely unclear or your missing the point.

I Have  two problems with the code:-

#1

I would like each DM variable to have its own text NOT "Alarm" if DM 1 - 10 = 11.

i.e

if DM[1] = 1 I want to set the LCD "CB Trip"  if DM[1] = 0 No alarm.

if DM[2] = 1 I want to set the LCD "Pump Error" if DM[2] = 0 No alarm.

if DM[3] = 1 I want to set the LCD "Sensor Error" if DM[3] = 0 No alarm.

ETC ETC for the entire list of alarms DM 1 - 20 for example.

As above, I still want the "moving list" function i.e alarm one  is displayed on line one,  alarm two is displayed on line two, if alarm one is cleared, alarm two will "move" into line one.

I appreciate the list doesn't move it just looks that way.

#2

When the the alarms "move up" i.e. from line 3 to line 2, line 3 isn't cleared.

I hope that's clear.  

Thanks again for the help.

OK,

That makes sense.  Are the 32 bit variables A - Z mapped? I cant see them in the modbus section of the manual?

Hi,

I'm using quite a few DM's to store a single value of 1 or 0,  my modbus master reads these DM's according to the standard mapping.

Is it possible to combine these DM's to form one 16 bit word each bit representing one of the DM's.

I'm working on a project where I need to get as much data from each PLC as simply and quickly as possible.  Ideally,  I would like to reduce my modbus word list from 100 words down to 7 (100 / 16) words with the DM values stored as a binary or decimal value.

last post tonight I promise!

Cheers.

Hi,

still struggling with these calcs!

I'm trying to calculate a pump actual and total flow in litres / second.

first I have to convert the pump data from m3/h to L/s,  to do this you divide the m3/h by 3.6.  Then its just a mater of  multiplying the answer by the pump operation time.

I then need to add the calculated running flows together to a total flow in litres.

my code below.

DM[23]= DM[22] / (36/10) ' PUMP FLOW RATE IN M3/H / 3.6

DM[24] = DM[23] + DM[24] ' = TOTALISER UPDATED EVERY 1 SECOND.

i.e 3 (m3/h) / 3.6 = 0.83 L/S

X 10 seconds = 8.3 litres total.

The trouble is due to the fact 0.83 is not an Integer and is rounded to 1,  now my pump flow is 1 L/s.

an you provide an example using the "Fixed point" representation described above.

Ok,

Thanks.

Hi,

I'm trying to run some simple calculations through the PLC using the memory space and I'm not getting the correct values back.

Calc:-

DM[20] = ((DM[18]*DM[18])*(3142/1000)) * DM[19]
DM[21] = DM[20] / 1000

'  DM[18] = RADIUS IN CM                     (4)
'  DM[19] = HEIGHT IN CM                     (10)
'  DM[21] = VOLUME IN LITRES
 
' VOLUME = pi * (r * r) * h / 1000 = LITRES

The answer on my calculator is:-

(4 X 4) * 3.142 * 10 = 502.72

/ 1000 = 0.50727 L

I know the DM[XX] are Integers that can only display whole numbers.

I guess my question would be how can I convert the above into Decimal and can I display this in the data memory?

Many thanks

Hi,

Thanks for the response.

I don't need a high or low priority, if the alarm is active it will be in the list, if the list is full (4 alarms) any additional alarms will not be displayed.

when one of the four alarms in the list is cleared, any alarms not currently displayed will now appear in the list.

I only have around 10 alarms.

is the code the same as above??

Hi,

I'm looking to install 2 TMD's in a hot standby configuration.   Both TMD's will run in parallel with each other.
An HMI will be attached to each PLC RS232 comm's port but only reading / writing to one via modbus etc

Each PLC will monitor the other PLC's watchdog output (is there one?) if the watchdog contact is active the comm's will be switched over via output relay or similar to the second PLC and vice versa.

This leaves me with a problem, the data in the first duty PLC will need to be constantly synchronised with the standby PLC so when the PLC's change over any timer values,output commands written from the HMI etc are the same.

I will probably need to use at least two extra TMD's as remote I/O in the field collecting data, reading inputs etc.  this will also need to "switch" onto the standby PLC......

Is this possible? has it been done before??