Review

This book explores the world of Visual Basic 6 programming with respect to real world interfacing, animation and control on a beginner/intermediate level. The original title of the book was "Visual Basic 6 : Real World Interfacing, Animation and Control. The title was changed by the publisher's marketing department much to the Author's chagrin. This is VB book that demonstrates how to create an HMI (Human Machine Interface) from scratch. A Home Monitor application was selected to provide a broad appeal to all readers.

Most of the Visual Basic books on the market today and in the past do a very good job of describing the various control elements of Visual Basic and how they work. Typically examples are provided for programming some type of data base application of one sort or another. The focus of this book is interfacing to an external device via the serial port, showing the status of this device by animating objects on a Visual Basic form and then controlling this device. The Allen-Bradley Micrologix PLC by Rockwell Automation is one serial device that will be explored. An alphanumerical display is another serial device that will be investigated.

The acronym "PLC" stands for Programmable Logic Controller. PLC's are the fundamental building block in industrial control systems today. Typically a PLC consists of inputs, outputs, a central processing unit, user memory for control functions, a proprietary operating system and a serial port. With a PLC, input devices such as push buttons, limit switches to name a few are wired into inputs and output devices such a lights, horns, motor control relays and so on are wired to outputs. All the cross wiring required to implement some desired function is accomplished with software rather then hard wiring and additional components.

The intent of this book is Visual Basic but it will discuss to a certain degree the architecture and the programming of Programmable Logic Controller. The most popular language used to program a PLC is called "Ladder Logic". Ladder Logic is modeled from the way that one would actually wire up devices to relays. Input devices are represented as contacts and outputs are represented as relay coils. Essentially each rung of ladder logic is a graphical form of a Visual Basic IF THEN statement. Typically the PLC instructions set supports internal timers, counters, math functions (integer and real via floating point), move functions, Boolean functions and communication functions. The Rockwell Automation Micrologix PLC was selected because it is a popular, powerful, inexpensive PLC. Most of the material presented on the Micrologix PLC will also apply to other manufactured PLC's.

The application example presented in this book will be that of using the PLC as home monitor. This example is more appealing and easier to understand as opposed to implementing an example of a wastewater pumping station with level control using a variable frequency drive. It is inevitable that some day the PLC or some form of the PLC will be controlling all the electrical operations of a house.

As a home monitor the PLC will monitor the following digital inputs: front doorbell pushbutton, rear doorbell pushbutton, front door open sensor, rear door open sensor, first floor HVAC system on, second floor HVAC system on, water pump on, and mail box open sensor. In addition to the discrete digital inputs, five temperatures will be monitored (outside air, crawlspace, first floor, second floor and Great Room) and water pressure of the water pump will be monitored. Two PLC outputs will be used to drive a horn and turn on a blower fan under the control of the Visual Basic program.

First a Visual Basic 6 program will be developed that communicates serially with the PLC using Rockwell Automation Allen-Bradley protocol. This protocol will be considered to perform two tasks: an "unprotected read" and an "unprotected write". The structure of this binary protocol will be examined. The software developed to perform these tasks will be simply and clearly presented.

Another Visual Basic 6 program will be developed that interprets the collected information and animates objects on a Visual Basic form accordingly, such as a door shown in the open or closed position along with an associated time/date stamp as to when it was opened or closed. Temperature and other data information will be stored as monthly files on the harddrive in CSV(comma separated values) format. Microsoft Excel can then be used to provide a graphical representation of the data contained in these files. Wave files will be launched to provide audio annunciation of certain events.

A stand-alone full function-graphing program will be developed that interprets the data log files. This program will automatically update in conjunction with the data log file.

A second serial port will be used to provide textual based status information from the Visual Basic home monitor program to a remote alphanumerical display.

Through the process of developing the home monitor program many aspects of Visual Basic programming will be studied. Emphasis will be placed on keeping the software as simple as possible. The lessons learned in this book will be invaluable for future serial and animations projects.

All programs presented in this book and contained on the companion CD have been thoroughly tested. I hope you like it as much as I enjoyed writing it and creating the software. Tom Leonik

19 of 22 found the following review helpful:

Just use the softeware which comes with the PLC  Oct 12, 2002
By ----neal M. Shaw
I was very excited when I found this book and read the reviews. Chapter one was a small intro to visual basic. The first half of chapter two explained how to input and output with the serial port, great. Then I get to the second half of chapter two and I read that all I need to do is go and get a PLC interface. Why bother with the book then. If I'm going to spend hundreds of dollars on a PLC interface, just buy one which has software, and use the software which comes with it. Don't get me wrong, I'm sure for someone who already has a PLC and needs to revise their programs, this book would be valuable, however for the person who is interested in using the serial port to acquire ideas and tips for simple input/output application around the home, it is frustrating. Maybe the title should be Programming for the PLC in Visual Basic 6. That would be much more appropriate.

11 of 12 found the following review helpful:

Great Book and reference  Nov 10, 2002
By Tim Singer
I've read a lot of books on VB and PLC's but the book that I think about most and use as handy reference is Tom Leonik's --Home Automation Basics - Pratical apps using VB6. This book is fun and to the point. The example of a home monitor is cool and the material presented in the book can easily be applied to many different applications.

The one reviewer who stated that you needed PLC software... obviously did not read the book. PLC software is only needed to program the PLC. The PLC in this application performs conditioning of inputs and stores key information in non-volatile ram. The book creates a driver to communicate with the PLC in VB no other software is required. This is an amazing task and it works.

8 of 9 found the following review helpful:

Nice Reference for my Visual Basic Manufacturing Apps.  Dec 22, 2000
By Stanley D. Musick
Credit is do to Mr. Leonik for producing this book. I'll use it as a nice reference for some of my manufacturing applications written in Visual Basic. The methods covered in this book can be applied to many real world events. Thanks for taking the time to share your knowledge.

Visual Basic Applications Programmer {Specializing in Data Acquisition & Process Control for QA and Industrial Environments.}

8 of 9 found the following review helpful:

Not just for home automation...  Nov 22, 2000
By Mark V Lane
Great job! I found this book to be very useful for more than just home automation. I have read several OEM protocol manuals in attempt to learn PLC communication. Leonik's book truly cleared the water for me. The principles of serial communications are explained clearly and I was able to apply the examples even with my limited knowledge of Visual Basic. Although the book focuses on the Alan Bradley protocol, the clear explanation helped me to understand other protocols such as DirectNet and Modbus as well. I'll be reading everything Leonik writes from now on!

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