PLC Programming: Internal Memories

Internal memory is where the results from combinations of inputs and outputs can be stored, and this stored value can take different names such as:

Bits (B)

Mark (M)

Flag (F), etc.

From a technical point of view, internal memory is considered a virtual output; this means that it does not physically activate an output like a contactor, but rather it is data stored in memory and can take the values of 0 and 1.

Its advantages are reflected in:

•It simplifies problem-solving.
•Fast diagnosis of faults, etc.

The interpretation of how it works will be clearer when we develop the following example:

HYDRAULIC PRESS 
TECHNOLOGICAL DESCRIPTION:

Automate a hydraulic press so that it can only operate when the protective grille is closed (S3 and S4). Additionally, two pushbuttons (S1 and S2) must have been pressed, and the piston must be in its initial position (S5).

If, during the descent of the piston, the grille opens or either of the two push buttons is released, the piston stops instantly.

When the piston reaches the lower limit (S6), it immediately begins its return to the upper limit. During its return, the protective grille can be opened and the pushbuttons released.

All pushbuttons and limit switches are normally open in their rest state.

The following is requested:

1. SORTING LIST

TICKETS

DEPARTURES

2. CONTACT DIAGRAM

3. FUNCTIONAL PLANE

4. CONNECTION DIAGRAM