PC Based Database Integration

Overview

PC based PLC database integration is a fast, affordable, and very flexible design to exchange data between your PLC equipment and database server systems.

Database information is stored on one to many database servers. An application program called an "interface" is created that will facilitate communication between the database server and PLC. Using some unique identifier (usually, a bar code scan), a database transaction is requested. Data from the database server is transferred to the PLC. Once operation is complete, information is written back to the database server (if required).

PC (Personal Computer)

The computers normally used with this design are usually more robust industrial computers that use a touchscreen. Typically, these types of computers are panel mount devices that reside on the face of an enclosure. However, any computer can be used that fulfills any hardware minimum requirements.

In some cases, one PC and application interface can accommodate more than one PLC. The ability to use this design is determined on a case by case basis. However, this is normally not recommended due to performance and serviceability issues, but in some cases, this may be an adequate design.

Database

A SQL server database is required for storing data. Bevan Engineering can design this database and all it's associated tables for you. Once it's time to implement your project, your IT department can receive a copy of this database in it's detached form and attach it to your existing system.

If data from your existing server system is required, a stored procedure can be provided that will allow that access. This type of support is typically found in-house and minimizes the amount of access required from your administrators.

Database Interface Application

A software application is written (usually in VB.NET) that communicates with both the database server and PLC. All connections require an ethernet connection. If the PLC is not network capable, a NET-ENI device can convert the PLC's serial port to an ethernet port. In some instances, a PLC's serial port can be used directly, but this method is not recommended.

The design of an interface application is almost the same (from a structural standpoint) for any application. First, a unique identifier is required for any production process. Usually, this is a bar code label. This bar code label can contain serial numbers, models numbers, or any other type of information that would allow information to be found in the database.

Once data is received from the database system, it is transferred to the PLC. The application interface will wait for the the process to be complete (pass, fail, abort, etc). Once the process is complete, information is written back to the database server. The amount of data received or transmitted is virtually unlimited. Once this information is in the database, the data can be used for a multitude of reasons - production statistics, error proofing, etc.

PLC

Bevan Engineering can modify any existing PLC logic to accommodate information received from your database systems. Conversely, if you choose to have your internal resources perform this portion of the project, they will be provided with a very detailed design spec stating specifically what needs to happen. "Hooks" will be provided (areas in memory data will be written to and read from) so development and debug activities can be performed in parallel.

If this is a new process or you choose to replace an older PLC to something more robust and modern, a new PLC program can be provided to you.

 

Strengths and Weaknesses
Strength	Weakness
Easy to modify/update	Hard drive/system can crash
No overhead expenses	All or part of system can become obsolete
Very flexible	Requires special programming skills not always found in-house
Excellent fault tolerance
Online SPC available