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Old July 5th, 2012, 05:58 AM   #1

Coulombboy is offline
Join Date: Jan 2012
Location: Makati City
Posts: 70
Product Totalizer Logic using Siemens S7-300PLC

Hi All,

I am currently working on a project of which we have used s7-300 PLC, and I am new to it. I need to provide a totalizer logic using analog signals coming from a weighfeeder. The totalizer engineering unit shall be in tons and weighfeeder signal is in tons per hour.

I have provided a 1 second pulses using a timer, and a math function that divides Tons/Hour into 3600sec to get Tons. And as my 1 sec pulse bit is true
the output ton will be added to the assigned data for the total weight of product produce. Unfortunately, I cannot make it work and i am having problem on some of the functions and these follow:

1. I have used FC105. In my HW config, analog inputs are 12bit. based on help fc105 input range is 0-27648 unipolar. Is this also the image of the analog input? 0-10V = 0-27648? 12 bit image is 4095. Can anyone suggest a better mean of scaling analog inputs?

2. For the totalizer, Im trying to do something which i have done using AB PLC. Let a = total product. And every pulse, i let a = a + b, where b is the quantity added to a. For this siemens plc, i have used the function ADD_R.

IN1 = md100
IN2 = md104
OUT = md 104

Where md100 = Weight delivered by conveyor every 1 sec in Tons
derived by scaling AI in TPH / 3600
md 104 = Total weight delivered by conveyor in Tons

Unfortunately it didn't work. MD104 do not update every 1 sec.

Should you guys done something alike, please let me know and kindly give me some advice so i can solve this problem. Thanks much in advance.
From nothing to something..

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Old July 6th, 2012, 02:17 AM   #2

jmsmoreira is offline
Join Date: Jun 2011
Location: Maia
Posts: 188
it might be better to post your code here, so we can take a look
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