Allen Bradley PLC Basic Math Instructions

Allen Bradley PLCs are widely used in industrial automation, and mastering the basic math instructions is crucial for programming them effectively. This guide will provide a fundamental understanding of these instructions, enabling you to perform essential calculations within your PLC programs.

Common Math Instructions

Allen Bradley PLCs offer a variety of instructions for performing mathematical operations. Some of the most common instructions include:

Instruction	Description
ADD	Performs addition of two operands.
SUB	Performs subtraction of two operands.
MUL	Performs multiplication of two operands.
DIV	Performs division of two operands.
ABS	Calculates the absolute value of an operand.
SQR	Calculates the square root of an operand.
SQRT	Calculates the square root of an operand.
SIN	Calculates the sine of an angle in radians.
COS	Calculates the cosine of an angle in radians.
TAN	Calculates the tangent of an angle in radians.

Example: Addition

Let’s illustrate the ADD instruction with a simple example. Suppose you want to add two values, 10 and 5, and store the result in a variable called ‘Sum’.

ADD Sum, 10, 5

In this instruction, ‘Sum’ is the destination variable where the result will be stored. The values 10 and 5 are the operands being added.

Example: Multiplication

Similarly, to multiply two values, 12 and 4, and store the result in a variable called ‘Product’, you would use the MUL instruction:

MUL Product, 12, 4

Applying Math Instructions

These instructions can be used in various PLC applications. For instance, you could calculate the speed of a conveyor belt by dividing the distance traveled by the time taken. Or, you could determine the volume of a tank by multiplying the area of its base by its height.

Understanding Data Types

It’s important to note that the data types of the operands and the destination variable should be compatible. For example, if you are working with integer values, ensure that all the variables involved are defined as integers.

Conclusion

Mastering basic math instructions in Allen Bradley PLCs is essential for creating efficient and accurate automation programs. By understanding the common instructions and their applications, you can confidently implement calculations within your PLC projects. Remember to consult the Allen Bradley documentation for detailed information on specific instructions and their syntax.