The Components of a Bar-Code Tracking System Continued...

Bar-Code Readers

Choose a bar code reader that matches your needs from the many different types that are available (figure 5). You can choose from wands, charge-coupled devices (CCD), lasers, portable data terminals (PDT), and readers based on a personal digital assistant (PDA). You may need to balance convenience with your budget in determining which types of readers to include in your system and how many you will need.

Figure 5—You can use many different types of equipment to scan bar codes.

Decoding—Decoding readers translate the symbology of the bar code into decipherable data before sending it to the workstation. Nondecoding readers simply capture the code and forward it to the processor. A system using a nondecoding reader must have a separate hardware or software decoder.

Most hardware decoders are the keyboard wedge type, which allow the processor to accept scanned data as keyboard input. Figure 6 shows an ordinary hardware decoder. Both the scanner and the keyboard plug into the decoder. The decoder plugs into the keyboard port on a workstation. Some decoders are RS232 (serial) models that translate undecoded signals into ASCII format (letters, numbers, punctuation symbols, and other symbols) and send it to the workstation’s serial port.

Figure 6—The keyboard decoder shown here allows
RS232 devices to be used without additional
hardware or software configuration.

If your system includes several portable readers, you could save $100 to $200 per reader by buying nondecoding readers and a separate decoder for the computer or docking station.

Connection Types—Fixed readers use a variety of cable connections, some of which are shown in figure 7. Cable connections are not interchangeable among most bar-code readers. Readers are programmed at the factory to work with a specific cable connection. Some readers can use multiple connection cable methods, but must be reconfigured whenever the connection method is changed. If a reader is to be used with different workstations or in the field, a programmable scanner may be an option.

Figure 7—These two readers are the same model, but use different
methods of connecting to a computer.

The simplest method of connecting a scanner to a computer is through the keyboard port. This method is often called a wedge connector, because the reader is “wedged” between the computer and the keyboard as shown in figure 8. The keyboard and scanner each plug into an arm of the “Y” cable, and the base of the Y plugs into the keyboard port on the host computer. This connection method will work with any program that reads keyboard entries. A decoding scanner or a separate hardware decoder must be used with a wedge connector.

Figure 8—This CCD (charge-coupled device) bar-code
reader uses a keyboard “wedge” cable configuration.

Universal serial bus (USB) connections for fixed readers also use Y cable adapters. However, the scanner’s cable is attached to a USB adapter (figure 9). The USB adapter plugs into the USB port on the back of the workstation. The keyboard remains plugged into the computer’s keyboard port and the third arm of the Y remains unused. This connection method is common with laptop-based systems. Data flowing through a USB connection are read as keystroke entries.

Figure 9—A laser bar-code reader with a USB adapter.

Personal computers, laptops, UNIX terminals, and many other electronic computing devices contain RS232 (serial) ports. The small D-shaped port with nine pins on the back of a standard personal computer is an RS232 port. Connections made using these ports are commonly called serial port connections or DB9 connections. When the bar code reader is used with UNIX or another operating system that supports more than one terminal, the bar-code reader acts like a second keyboard.

An RS232 wedge cable connects the scanner to the system. Scanned data will appear as characters on the terminal’s screen, just as if a user had typed them in.

On DOS- and Windows-based systems, the computer will ignore the signals though an RS232 serial port unless a communication protocol has been set up. The easiest method of establishing a communication protocol is to purchase a software program. Some program suppliers are listed in the Additional Information section of this report. These programs convert scanned data so they emulate keyboard input to the computer. Another method is to write your own data conversion program with a programming language such as C++. A third option is to use a basic serial communications program to save scanned data in a text file that can be imported into the inventory program.

You may need to configure the RS232 ports on both the computer and the reader so they have the same settings. The manual with the reader will contain instructions on configuring its RS232 settings. You can find the current serial setting on Windows computers by clicking on the System icon in the Control Panel window, selecting the Hardware, Device Manager, and View Devices by Connection options, highlighting the correct COM communications port and displaying its properties.

Fixed Readers—Fixed readers physically attach to a workstation or network through a cable. Wands, charge-coupled devices, and laser scanners all come in fixed-reader versions. Corded models limit mobility to the length of the cord.

Wands are contact readers. Figure 10 shows one of the many types of wand readers. To read a bar code, the wand must be smoothly brushed across the label perpendicular to the lines.

Figure 10—This wand reader uses a keyboard wedge
cable. The separate cable is an adapter for older
IBM-compatible models.

These pen-shaped devices are the least expensive scanning option and are available in most connection types. Using a wand to consistently read bar codes requires practice. Extended use can cause fatigue. Some wands will not read high-density bar codes and have trouble with damaged labels and uneven surfaces. Wands are not recommended for intensive bar-code scanning applications.

Like wands, charge-coupled devices (CCD) require physical contact to scan a bar code but they use a point-and-shoot method similar to a laser scanner. Figure 11 shows one type of CCD. CCDs are available for most types of connections. CCD readers are intermediate in cost between wands and lasers. CCD devices use less power than lasers, so they may be a good choice when used with a laptop or portable data terminal.

Figure 11—A CCD reader is a good choice when you
don’t need to scan from a distance.

Laser bar-code readers do not have to contact the bar code. Figure 12 shows a very futuristic-looking laser scanner. If you aim the reader and pull the trigger, the device will read the bar code. Ranges vary from 3 inches to 30 feet, depending on the bar code’s density and the range of the laser. Advantages include the ability to read uneven surfaces and poorly printed bar-code labels, and better durability in some models. Lasers seem to be the most ergonomically comfortable scanners, but they require more power than CCD devices and deplete batteries more quickly. Laser bar-code readers cost about twice as much as a CCD bar-code reader.

Figure 12—Laser bar-code readers are a
popular option because they can
scan from a distance.

Cordless Readers and Adapters—Cordless laser readers are the most common type of cordless bar-code label reader. Laser readers use a base station that connects to the workstation like a comparable corded model. The base station uses radio frequency (RF) signals to communicate with its remote scanner. Cordless scanners are significantly more expensive than wired scanners, but are useful in situations where bulky items cannot easily be brought to the scanner. The range of cordless scanners depends on the model and the operating environment. Interference may occur from multiple RF scanners operating at one time, microwave ovens, cell phones, and other radio sources. Some models have features to correct these problems. RF communications are one way or two way, depending on the model. In one-way setups, the base station will beep when data is received, so the user must stay within earshot to confirm successful transmission. In two-way setups, the base station will return a signal to the scanner confirming that the data was received.

Adapters are also available that will turn some corded scanners into cordless scanners. These adapters are costly. Adapters work only with certain bar-code readers and connections, so you will need to check to make sure that a particular adapter will work with your system.

Portable Readers (Batch Readers)—Portable data terminals and personal digital assistants can be configured for bar-code tracking. They are powered by batteries and used for collecting and storing information at locations remote from the processor. The data are uploaded as a “batch” when the portable reader is connected to the processor.

Portable data terminals (PDT) have a keypad, screen, onboard memory, operating system, and communication ports. Some contain a built-in laser scanner, others include a connection port for a laser, CCD, or wand reader. Figure 13 shows a PDT with a separate laser reader. Most PDT software is easy to understand, taking only a few minutes to an hour to fully learn. You can expect to pay at least $1,000 for a basic PDT. More complex models have correspondingly higher prices.

Figure 13—This portable data terminal uses an RS232
connection to a laser bar-code reader.

Basic PDT models store scanned items in sequence. More complex models allow the user to define input variables. Deluxe PDTs contain sophisticated programming capabilities and extended memory storage. They allow the user to build custom programs that can respond to keyed or scanned inputs, download inventory files, and manage the main database from the PDT. Most PDTs with advanced programming capabilities come with a program generator so that a personal computer can be used to set up the data collection program. Once the collection program is complete, the program is loaded onto the PDT.

Each PDT uses an RS232 serial cable connection and communications program to connect directly to its host terminal or to establish a connection through its docking station. The PDT manual will contain instructions for configuring RS232 ports on the computer and scanner. You can find the current serial setting on Windows computers by clicking on the System icon in the Control Panel window, selecting the Hardware, Device Manager, and View Devices by Connection options, highlighting the correct COM port, and displaying its properties.

Most PDTs transfer data to their hosts using text files. The user must open the text file and the database or spreadsheet and copy individual values from the text files into the database or spreadsheet. Specialized inventory software can directly communicate with some PDTs, so the scanned data goes directly into the spreadsheet or database. Packaged systems containing compatible PDTs and software are available.

Bar-code readers for personal digital assistants (PDA) use a laser. You may be able to purchase a bar-code reader expansion pack for your existing PDA. New PDAs can be ordered with built-in bar-code readers (figure 14), or with a bar-code expansion pack. The laser reader on your PDA will not work without a well-charged battery.

Figure 14—The Symbol SPT 15xx model series
are popular entry-level personal digital
assistants with an integrated laser
bar-code reader.

Unless PDAs are configured for wireless communication, they use the batch method to transfer stored data. PDAs use a cradle connection through a USB or serial cable. Some operating systems on newer PDAs require the Windows 98 or newer Windows operating systems.

Bar-code expansion packs for PDAs and PDAs with built-in readers contain system files to decode bar codes and send the data to the appropriate data storage software program. Data is normally routed to the program that is currently running, but some models allow the user to configure the PDA to launch the proper program automatically when scanning begins.

Some PDAs include software that can be used to store data, or you can purchase separate software. The software stores data in text files that are “hot synced” into the workstation when the PDA is connected to the processor. Text-based storage software works with almost all inventory programs, but some systems will not import or update data automatically.

Some PDA database programs can be customized to mimic the main database on the workstation. This feature can be helpful when you need to check information at a remote location, but it uses a lot of memory and slows the operation. Each time the PDA is hot synced, the main database tables are automatically updated.

Certain computer-based inventory software programs include partner programs that allow data to be transferred easily between the PDA and the main database. They function like the more elaborate database programs described above.