Selecting the Right BarCode Printer
There are four primary types of printing technology available today: direct thermal printing, thermal transfer printing, impact printing, and laser printing.
Direct Thermal Printing
Direct thermal printing employs a print head with regularly spaced electrodes to create an image on specially treated paper. In operation, conduction of electrical signals, in an array of tiny gaps between electrodes, applies heat to the substrate.
A chemical reaction, created by the applied energy, forms small dots that comprise text or graphical images. Historically, thermal paper supported limited longevity, particularly when exposed to heat or direct sunlight. Direct thermal printers have a small number of moving parts, which bolsters mechanical reliability, and only paper is consumed in the printing process.
Thermal Transfer Printing
Like direct thermal, thermal transfer technology employs a thermal print head to create an image on a substrate. In operation, ink is transferred from a ribbon to the substrate. Therefore, additional components include a ribbon supply and take-up mechanism, and ribbon, which must be replaced after use. Thermal dye transfer printers that produce high-quality photo images are special adaptations of this technology.
Impact Printing (also known as Dot Matrix)
Impact printers use a moving hammer to transfer ink from a ribbon onto paper. The impact enables these devices to print multi-part forms, automatically generating several copies of a document simultaneously. Because of the moving parts involved, impact printer lifetime can be limited and maintenance costs higher relative to thermal printers.
Paper and ribbons make up the consumables for this class of devices.
Laser Printing
Laser printers use digital copier technology to inscribe an image on a drum, which is then transferred to paper using toners. In general, laser printing engines are bulkier than other printing technologies and are generally considered expensive to operate.
Consumables here include paper and toner cartridges.
This paper focuses on direct thermal printing technology as the ideal choice for embedded systems developers—particularly when designing for unattended applications. Direct thermal printing technology satisfies embedded systems requirements because it has comparatively high reliability ratings, minimal maintenance requirements, less frequent need to replace consumables, competitive print speeds, and the flexibility to print on a variety of media.
For special application with bar-code printing mostly direct thermal and Thermal Transfer Printing used


Meeting Cost Targets
A number of factors can significantly influence the cost of an embedded printing project.
These include: form factor, customization needs, system integration timelines, system manufacturing requirements, and maintenance needs. The considerations for these variables are discussed throughout this paper to give you a better understanding of the alternatives and trade-offs.
In general, when faced with rigid cost parameters, it is advisable to consult with the printer manufacturer as early as is feasible in the design cycle. By doing so, you will have more opportunity to assess the alternatives, to optimize the system design for costs, and to avoid design missteps that can adversely affect your project’s budget or release schedule.
Mechanical, Electrical, and Software Integration
Electrical and Software Integration
To address electrical integration, you should select the printer mechanism and controller combination that matches the power and voltage levels you have available in your application. Most high performance thermal printer mechanisms require a nominal 24- volt source to provide the electrical discharges to mark the paper. This often requires the addition of a DC/DC step-up converter or other power supply. Portable devices can operate from as little as 5 volts. In addition, the controller will require a well-regulated 3 to 5-volt DC source to power the on-board electronics that control the mechanism.
Thermal printer power consumption is generally quite reasonable, and usually will not exceed normal power consumption expectations for modern electronic products. Special heat sinking equipment is generally not required for the printer, nor are special cooling capabilities, other than a standard system fan that moves air through the chassis to cool other system components.
The interface that moves data from the host computing system to the printer controller, and ultimately to the thermal print head itself, is another important area for electrical integration. The most common hard-wired interface options include: serial links (RS-232, TTL), parallel ports, Universal Serial Bus (USB), and, in some cases, Ethernet. Wireless interfaces, such as Bluetooth and Wi-Fi, are typically used in portable, standalone printer applications, and not in embedded solutions.
Software integration is primarily dependent on the availability of appropriate printer driver software or host-based software to issue printing instructions. Many widely used operating systems, including Windows, Linux, and JPOS, incorporate a printing system for a printer driver to interact with to produce the desired output. For operating systems that do not have a printing system, such as Windows CE, the manufacturer should provide a software development kit (SDK) to facilitate integration.
Fulfilling Performance and Output Delivery Requirements
Printer performance varies based on a number of factors. Designers should expect some correlation between performance and operating voltage, cost, and, to some extent, mechanical dimensions—faster printers typically require larger motors. Generally, an embedded thermal printer running at ten inches per second, or three inches per second for a portable application, is considered a higher performance device.
Thermal printers offer a number of output delivery options, including a manual tear bar and an automatic cutter for separating the output. For unattended applications, it may be desirable to incorporate a looping presenter, with an automatic cutter, to prevent users from pulling paper during the printing process. This can help to avoid unintended disruptions and potential maintenance issues. A partial auto cutter, combined with a receipt retractor, presents another alternative. With this configuration, the system can be programmed to withdraw the receipt to a holding area, if a specific time interval has passed and the receipt has not been removed by the user. This avoids littering the immediate area.
Other examples of application-specific delivery capabilities include: a built-in label “peeler,” to ease the manual effort required by the user when printing in large volumes; and a sensor or control mechanism that limits the flow of printed labels. The sensor capability helps the user by only dispatching a new label when the previous output is removed.
Meeting Application-Specific Media Requirements
Direct thermal printouts are available in various sizes. However, most applications involve labels, receipts and other output that are no more than 4 inches wide (approximately 112 mm). Typically, direct thermal applications only require black text or graphics. Multi-colored printouts can be created by varying the level of energy applied to specially coated thermo-sensitive paper.
Thermal printing technology can be used with a range of substrate thicknesses. To ensure success, it is critical to choose a printer that is rated for the appropriate media thickness and to only use paper that has been qualified by the manufacturer. As a caveat, however, note that some vendors may only qualify their own proprietary formats for labels and other substrates, as a means of ensuring residual sales.
Other important output criteria include:
Output Resolution
Current thermal printing technology can support up to 600 dots per inch (DPI), although the vast majority of applications can be addressed more cost effectively with 203-300 DPI printers.
Virtually all thermal printers come with a selection of standard fonts built into the controller firmware. The bar code format can be selected by sending the corresponding ID number for the desired code.
Commonly used image file formats, such a JPEG or bitmap can be used with a thermal printer to produce, for example, a coupon or company logo. Although, very high resolution files can affect printing performance. The paper converter or manufacturer should be consulted when pre-printed security marks are needed, or to help address other more elaborate paper requirements.
Maximizing Reliability and Minimizing the Need for Maintenance
A long and trouble-free operating life expectancy is a key factor in selecting a thermal printer. While the individual lifetimes cannot be accurately predicted for any device, certain specifications can be used to gauge product reliability. These include a:
  • Minimum rating for the number of total dots produced by the print head (measured in electronic pulses). 150 million pulses is considered a very high rating for a 24-volt printer.
  • Minimum rating for total length of output that can be produced (in kilometers). 150 kilometers of total printing is considered a high rating for a 24-volt printer.
  • Minimum rating for total number of cuts. A 1-million-cut rating generally indicates a very durable auto-cutter.
Durability may also be a key factor for particular applications. For example, you may need to plan for a shock-mounted design to ensure continued operation after repeated drops from a specific height to a concrete surface. Similarly, environmental specifications for humidity and ambient temperature will help you judge whether the printer will perform reliably on a cold winter day without special protection.
Providing System Monitoring and Problem Notification Capability
As with any electronic devices, thermal & thermal transfer printers cannot be built to run in perpetuity. Paper replacements are periodically necessary, and unattended systems can be subject to extreme conditions or mistreatment by users. To reduce potential problems and downtime, printer monitoring provides signals to the host computer system for important conditions such as “paper low,” “paper jam,” and “paper out.” The host system can then alert a remote maintenance facility to correct the problem, providing improved uptime and a better overall user experience.
Direct thermal printing technology provides the ideal solution for embedded system printing applications where long life of printed information is not the case. By deploying thermal transfer printers you can be sure that information will be stored without problem for a long period of time, even when exposed to heat or direct sunlight.
By engaging the printer usage in advance, to explore the issues raised in this paper, you can significantly bolster the return on your investment and minimize project risk, even for the most complex and demanding systems.