PLC logic and drive coil command (LD, LDI, OUT) usage and usage precautions - Database & Sql Blog Articles

1) Usage Example

Figure 1 demonstrates the use of logic coil drive instructions in a PLC program. This example illustrates how to control an output based on a specific input condition, making it a fundamental concept for beginners learning PLC programming.

2) Important Notes for Use

1) The LD instruction represents a normally open contact at the beginning of the circuit connected to the left bus. It is used to start a rung with an open contact.

2) The LDI instruction stands for a normally closed contact at the beginning of the circuit connected to the left bus. It is used when you want to activate a rung only when the contact is closed.

3) The OUT instruction is used to drive a coil and send a signal to an output. However, it should be noted that input relays (X) cannot be used with this command.

4) When using ANB and ORB instructions, the LD and LDI commands can be used to start contacts in series or parallel circuits. These instructions help create complex logic structures within the program.

5) For timers and counters, after using the OUT command, the coil must be set to a constant value. This ensures proper operation and avoids unexpected behavior in the system.

Understanding these basic instructions is essential for anyone working with PLCs. Proper application of these commands can greatly enhance the efficiency and reliability of your control systems.