PLC Program to Store Temperature Data of a Process at Different Time


This is a PLC Program to Store Temperature Data of a Process at Different Time.

Problem Description

Temperature of two tanks are being controlled. To display and compare temperature of both the tanks, graphical display is used. Update temperature of these tanks on the display every 5secs for comparison with respect to time. Implement this process in PLC using Ladder Diagram programming language.

Problem Solution
  • Using RTD PT100, we can calibrate value 00000 to 65536 into -2500-6500C and divide into 800 equal parts.
  • Use MOV instruction to transfer Input data into register for further conversion usage.
  • Convert outputs of temperature transmitters into equivalent Temperature in Centigrade.
  • To do this, divide input by value change per centigrade, we get temperature inside that tank.
PLC Program & Program Description

Here is PLC program to Store Temperature Data of a Process at Different Time, along with program explanation and run time test cases.

List of Inputs and Outputs
 I:1		= Input from temperature transmitter1	(Input)
 I:2		= Input from temperature transmitter2	(Input)
 I:3/0		= Start PB				(Input)
I:3/1		= Stop PB				(Input)
 O:4/0		= Master coil				(Output)
 N7:0 to N7:8	= Registers to store and process data	(Register)

Ladder diagram to convert data into equivalent temperature in Centigradeplc-program-store-temperature-data-process-at-different-time-01

  • When divided by total range of RTD PT100 that is -250 to 650 degree centigrade, we get 82 value change per Centigrade.
  • Hence when divided by 82, we get answer in centigrade.
  • Important thing to note here is that the input here will always be greater 23124 which is value when temperature is 32 degree centigrade that is room temperature.

Ladder diagram to update Trend display every 5secsplc-program-store-temperature-data-process-at-different-time-02

  • RUNG002, RUNG003 and RUNG004 updates temperature data in corresponding registers every 5secs.
  • Timer is in auto reset mode, hence timer will keep running till it is manually stopped by operator.
Runtime Test Cases
Inputs       Outputs                              Physical elements
I:3/0 = 1    O:4/0 = 1                            Start temperature displaying
T4:0/DN = 1  N7:7 = N7:1, N7:8 = N7:3, Accum = 0  Update temperature & reset timer

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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