Application digest

Pipe light to front panels with optics

Richard Present, Manager, Strategic Market Develoment, Dialight Corp.

Surface mount light-emitting diodes (LEDs) are point sources of light packaged for manufacturing compatibility. They require secondary optics to channel their light, usually at right angles, from the printed circuit boards on which they are mounted to the front panels of electronic enclosures. By contrast, through-hole LEDs use integral reflectors, lenses, and diffusants for this purpose.

The most common type of secondary optics are light pipes made of fiber-optic materials or molded lenses that act as conduits for light. Engineers use light pipes when LEDs are located at a distance from the front panel or emit light in a different direction. They're also useful when an application requires high-density arrays or uniquely shaped indicators. Light pipes provide added protection against electrostatic discharge because their polycarbonate construction isolates the LEDs.

Because they can't withstand surface-mount process temperatures, light pipes are attached after discrete LEDs are soldered on the board. The advantages of this approach outweigh the inconvenience of performing an additional post-process operation. These include greater flexibility in selecting LED size and shape, better access to the LEDs for rework and inspection, and the fact that alignment is less critical than with through-hole LEDs.

Light pipes interact only minimally with the front panel, so they do not pose a design burden. They offer changeable viewing surfaces, accommodating both backlighting and direct viewing in horizontal or vertical arrays. When properly designed, a single molded part can redirect light from multiple LEDs to different front-panel indicators without optical crosstalk. This reduces the installed cost per indicator position.

To be effective, light pipes must deliver as much of the limited light output of LEDs as possible to the front panel. This requires critical ray tracing to optimize their optical transmission performance. Molding techniques must be precise to minimize inconsistencies, impurities, and air bubbles in the plastic. The potential for light loss inherent in a surface-mountable component must be addressed.

To speak with a Dialight applications engineer, call (908) 223-9400.

Use robots for material handling problems

Rick Ware, President, Rankin Corp.

A system designed to transport blood samples demonstrates the flexibility that robots offer design engineers. Yamaha Robotics' engineering team based the design of this equipment on a modular automation system consisting of Yamaha two-axis FLIP robotic components operating in XY and XZ configurations. Each is governed by a DRC two-axis controller.

Robot models employed for the XY-axis configuration--the BLSII and BFS--provide standard stroke lengths of 1250 mm and 1050 mm respectively. For the XZ axis configuration, robot models employed are the 650-mm-stroke BFS and the 350-mm-stroke FS.

To enable the robots to grip and hold sample racks as they move from one testing station to another (each rack holds 10 blood vials), engineers used standard component parts to develop special finger tooling.

Developed, built, installed and programmed within 90 days--thus enabling the user to meet tight production deadlines--the system handles an average of 200 vial "parts"/minute. Because of the inherent flexibility of its modular design, the system has been adapted for other clinical laboratory applications by the user. Meanwhile, the programmable, high-precision components help keep system operating and maintenance costs low.

To speak with a Yamaha Robotics applications engineer, call: (800) 82-YAMAHA.