Advance Mathematical Function for PLC

We have many advanced mathematical functions like trigonometric functions, Logarithms, exponents, square root functions etc . For complex type of calculation we use CPT. some functions we use is listed below….

ACS (Value, Destination) – inverse cosine

COS (Value, Destination) – Cosine

ASN (Value, Destination) – Inverse sine

SIN (Value, Destination) – Sine

ATN (Value, Destination) – inverse tangent

TAN (Value, Destination) – tangent

XPY (Value, Value, Destination) – X to the power of Y

LN (Value, Destination) – Natural log

LOG (Value, Destination) – base 10 log

SQR (Value, Destination) – Square root

CPT (Destination, Expression) – Does a calculation

Let us suppose we have problem like

A = sqrt ( ln B + e^c  (a cos ( D ))………………………………… sqrt means square root

Solution:

We take LN function for natural log then we take XPY function for e^c. Now we use ACS for inverse cosine as question demands. For multiplication we use MUL, For Addition we use ADD and finally we use SQR function for final value to release from square root.

Before using any function we assign some address as shown below

A = F8:0

B = F8:1

C = F8:2

D = F8:3

Now we use function as I mentioned above. The below figure makes us easy to understand …..

FIG: An equation in Ladder logic

Here an equation has been converted to ladder logic. The first step in the conversion is to convert the variables in the equation to unused memory location in the plc. The equation  can then be converted using the most nested calculation in the equation such as LN function. In this case the result of LN function are stored in another memory location, to be recalled later. The other operations are implemented in similar manner.

The same equation could have been implemented with CPT function as shown in below. The equation uses the same memory locations chosen in above for A,B,C and D. In this case the expression is typed directly into plc programming software.

FIG: File Algebra Example