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Articles from 2004 In October

Valve Module Controls Conveyors Without a Central Computer

Valve Module Controls Conveyors Without a Central Computer

Engineers searching for a simple means of controlling miles of pneumatically-actuated conveyor lines may now have a way. A new valve module from Humphrey Products Co. (Kalamazoo, Mich.) eliminates the need for programmable logic controllers (PLCs) or centralized computer control, and yet still provides automated conveyor motion. The module, targeted at the giant warehouse conveyor lines operated by retail distributors, enables developers to apply a "zone control" technique to the automated movement of packages on a conveyor. By "talking" to pneumatic modules in upstream and downstream zones, the system can control movement of packages across miles of conveyor lines.

"We've broken down the distributed control of a conventional conveyor, and brought that distributed intelligence to each of our zones," says Rich McDonnell, business development manager for Humphrey Products.

To accomplish that, the system employs a valve module, a photoelectric sensor, air supply line, and a puck-like pneumatic actuator in each zone. During operation, the "photo eye" in each zone searches for approaching packages. When it spots one, it signals the module, engaging a three-way pneumatic valve. The valve, in turn, pressurizes the puck-like actuator. Operating in the manner of a conventional pneumatic diaphragm, the pressurized puck moves through its half-inch stroke, contacting a rotating drive belt, which engages the conveyor's rollers. As a result, the drive belt can then spin the conveyor's rollers.

By operating in this way, the system engages the rollers in its zone, typically about three feet long. The key to the system, however, is that as each zone activates, it also communicates with the next two upstream zones and the next two downstream zones. In that way, adjacent zones are always "prepared" for approaching packages, despite the fact that those zones are not connected to a central computer. The architecture of the system allows for 100 of the valve modules to be daisy-chained together. "Essentially, there's a wave," McDonnell says. "The rollers come alive just before a box gets to them."

Known as the Gen2, the module incorporates a three-way pneumatic valve, a 5-MHz Motorola microprocessor, and associated electronics for communications and voltage regulation. For diagnostics purposes, each hundred modules also work with a so-called "interpreter," which provides an interface between Humphrey's communication protocol (known as H-flex) and common field bus protocols, such as DeviceNet. As a result, the system can communicate with a centralized computing system employing Ethernet.

Humphrey engineers claim that the system offer advantages in terms of labor, time, and cost, when compared to more traditional pneumatically-driven conveyor systems. They estimate it is approximately 30 percent less costly to purchase and install.

"With the old way, there was a lot of heartache involved in the installation,' McDonnell says. "And it was more difficult to troubleshoot." In contrast, he says, the Gen2 module clips to the side of the conveyor. Moreover, it enables system integrators to eliminate the need for a PLC to run the conveyor systems.

"Now, you can program the system down at the rudimentary level, where it needs to be, and eliminate all of the programming and scanning time that goes on in the higher-level computing systems," McDonnel says. "Essentially, we're getting rid of the PLC and all the associated overhead, but still automating the conveyor operation."

The valve module clips to the side of a conventional conveyor.

Medical Imaging Sees Bright Future

Medical Imaging Sees Bright Future

The push for improved imaging is prompting research in the terahertz spectrum, where TeraView hopes to have an imager to market within three years.

Myriad factors are driving physicians to use high tech imaging systems to examine patients. Design engineers are responding by employing new spectrums for medical imaging as well as by melding more than one imaging technology into a single system.

The $6.6 billion medical imaging market will grow at 7.6 percent through 2008, according to market researchers at the Freedonia Group of Cleveland, OH. That growth will be driven by an increased demand for procedures that require imaging, a spokesman said.

TeraView Ltd. of Cambridge, United Kingdom, is employing the terahertz portion of the electromagnetic spectrum, which lies between microwave and infrared, to image healthy and cancerous tissue. The terahertz spectrum is being widely researched because the rays can be focused to improve image quality and because they are less harmful than X-rays.

The TeraView scanner that's currently being tested at a Cambridge hospital can image in 3D and distinguish between healthy and cancerous tissue, improving detection rates. The company hopes to have commercial hardware within three years.

In more conventional fields, advancements in technology now make it possible to combine different technologies, trimming both scanning time and floor space requirements. Royal Philips Electronics of Andover, MA., recently began shipping its Gemini PET/CT scanner, which acquires both functional and anatomical images in one procedure. Blending positron emission tomography (PET) and computed tomography (CT) in one machine helps improve patient throughput.

It lets physicians image the entire body in a single scan, minimizing the chance that problems can be missed during multiple passes. This timeframe is shortened by CT attenuation correction, which shortens processing time without degrading the image. The Gemini 16 has a mobile version that can be used in multiple facilities.

Motor Locks Up Reliability

Motor Locks Up Reliability

When solenoids failed to meet the durability needs of an automated lockbox for real estate agents, designers found the solution in a new DC micro motor. It's the same kind of motor also used in pill-dispensing machines, security cameras, and miniature robots, among other applications.

Measuring just 12 mm in diameter and 29 mm in length, Sanyo's new 12 GN series DC gear motors fit the compact design of SentriLock's REALTOR(TM) lockbox system, introduced in thousands of homes this past summer. Agents use a smart card to release the lock's shackle and then punch in a PIN to open the door to the compartment holding the homeowner's key.

"In locks, solenoids provide good power at the start but they will often lose power across the full stroke, causing the device to stick." notes mechanical engineer Shane Snipe, manager of Sanyo's DC Micro Motor Div. ( "What this application needed was reliable, constant torque."

Designed for applications that require intermittent actuation, the new motor weighs only 8.7 grams yet provides a starting torque of 300 mNm and a rated load of 20 mNm. It is available in four gear ratios: 1/75.7, 1/134.5, 1/196.6, and 1/297. No-load speed ranges from 62 to 246 rpm, depending on the model. Among other key features:

* No-load current of 120 mA.
* End play of 0.02 to 0.35 mm in the drive shaft.
* Lateral play of less than 0.04 mm at the tip of the drive shaft.
* Vibration of less than 40 m/s 2.
* Noise level below 55 dB at 5 volts.

In addition, the motor performed well in the REALTOR lockbox application during environmental tests by an independent lab, including temperature extremes from -40 F to 185 F, as well as salt air and moisture conditions.

In the lockbox system, the motor's gearhead attaches to a spur gear that drives a linear actuator in one direction to release the shackle-and in the opposite direction to open the door to the box containing the house key. Five patents are pending on the SentriLock system, involving both the mechanical operation of the system and its smart card technology. Visitors can view a demo of the product on

Engineer Scott Fisher, president of SentriLock, says he selected the Sanyo motor because it met the size, torque and operating voltage requirements of the application-5 to 6 volts. The motor connects to an off-the-shelf, dual-cylinder lithium battery (type 2CR5). By the fall of 2005, Fisher expects that more than 100,000 of the new lockboxes will be installed around the country, with a total market potential of over 2 million units. The system may also be adapted to other applications.

While other manufacturers, such as MicroMo Electronics and Danaher's Portescap unit, produce micro gear motors for precision medical devices and other high-end applications, Sanyo's Shane notes that the 12 GN Series design meets the market need for reliable, low-cost motors for high-volume applications. At just $3.00 a motor in quantities of 100,000 or more, the 12GN series are no more expensive than solenoids, adds Shane.

COMPACT MUSCLE: Sanyo's new DC micro motors, weighing just 8.7 grams, provide needed torque in applications where solenoids fall short on durability.

Besides the lock box application, engineer customers are selecting the new 12 GN series of micro motors for a wide range of applications, including: hand-held insulin dispensers, power tools for applying adhesives, miniature robots for hobbyists, security cameras, and automated pill-dispensing machines in remote areas. Another prime target: hotel door locks that need motors that can survive 500,000 cycles. "About one third of the hits we're getting on our website involve these new micro motors," says Shane.

Late this year, Sanyo will introduce even smaller 8 and 10 mm gear motors, aimed at such applications as lens movement in digital cameras and linear actuators for industry.

E2E Webcast Probes Hot Motion Control Trends

E2E Webcast Probes Hot Motion Control Trends

New power modules, electronic breakthroughs for autos, the spread of "soft motion"--these were just a few of the topics that leading engineers tackled in a full day of webcasts recently presented by Design News and industry partners.

The sessions, which engineers can view in archived form on the Design News website (, are the first in a new E2E (Engineer to Engineer(TM)) series that will feature prominent engineers addressing important technical issues.

With keynote remarks by well-known engineering entrepreneur Dick Morley, the October 18 E2E event showcased technologies that are transforming engineering design.

With the steady march of more software and electronics into the mechanical arena, speakers described a world of more compact, customized designs and faster development and production cycles.

"We're moving from mass production to point-of-sale manufacturing," said Morley, inventor of the PLC. Among his predictions for "Engineering in 2020": final assembly of autos at the dealership level and "living cars" with so much built-in intelligence that they can adapt to the environment without human controls.

Glimpse of tomorrow

Morley's vision demands enhanced power systems in cars, and engineering consultant John Miller gave his view on how to accelerate the move to 42V technology in a webcast devoted to "Hot Trends in Advanced Electronic Motor Drives." Miller, who has done extensive work with hybrid vehicles, described a method to introduce 42V functionality without the need to retrofit existing 14V power systems. At the heart of his dual-voltage scheme: high-current MOSFETs, digitally-controlled motion modules, and two 14V ultracapacitors.

In the same session, David Torrey of Advanced Energy Conversion presented his idea for a belt-driven starter/alternator system, based on switched reluctance technology, to save fuel in cars. Professor Tom Jahns of the University of Wisconsin also provided a glimpse of his futuristic projects: giant magnetoresistive field detectors that integrate sensors into power modules, as well as planar interconnect power modules that do away with wire bonds.

"Integration is the overriding theme in developing new power modules that will boost performance, lower cost, and improve reliability," said Jahns, who envisions smart motors that will combine all power electronics and controls within the motor frame.

Key enabling technologies

Other webcasts assessed the essential building blocks for motion control advances, particularly microelectronics and software. In the session on "The Latest Buzz on Digital-Based Motion Control," Kedar Godbole of Texas Instruments discussed the rapid increase in digital signal processors (DSPs) for motion control. That trend, he believes, allows engineers to better differentiate their products and build in more features.

With the price of DSPs dropping from a range of $2 to $15 per unit, Muhammed Mubeen of Motion Tech Trends agrees that this technology is not just for high-end applications. His engineering services company has included DSPs in designs as diverse as sump pumps, microwave ovens, and commercial paint sprayers. "It's getting to be that your application is obsolete if it doesn't have a DSP," said Mubeen.

Beyond digital-based motion control, Rahul Kulkarni of National Instruments sees a progression toward using software to create custom motion controllers, with the engineer choosing the processor and I/O based on price and performance requirements. For example, using the NI SoftMotion module for LabVIEW, engineers can build a reconfigurable motion controller on a PC or other platform, using a data acquisition device or Compact FieldPoint with servo updates up to 200 kHz per axis.

Among the new applications discussed in the "Understanding Soft Motion Control" webcast are projects that Professor Wayne Book is supervising at the Intelligent Machine Dynamics Laboratory at Georgia Tech. These include systems that provide "haptic" or tactile feedback sensations to simulate the control of heavy equipment .

Making the right choice

Other E2E webcasts tackled the tradeoffs involved when engineers choose control systems and motors for their projects. In the session on "Selection Guidelines for Central and Distributed Motion Control," Galil senior application engineer Todd Shearer gave examples of how flexible distributed control can provide the tight motion coordination of a central-control scheme-while saving money on wiring costs.

Similarly, in the "Basics of Motor Selection" webcast, Larry Roberts of Besie Die Handling explained how his company doubled throughput on a pick-and-place machine for semiconductor assembly by shifting from a stepper motor to a direct-drive servo motor.

Noting the increasing options that engineers have for motors, Todd Clark, founder of the Axis New England engineering firm, gave advice that may well apply to the entire fast-moving field of motion control: "There is a lot of innovation out there, so keep an open mind."

Faster I/O, More Memory

Faster I/O, More Memory

Rapid I/O: The XMC mezzanine cards have high bandwidth with memory for buffers.

The RapidIO interface is continuing to gain support, providing high-speed I/O for demanding applications. Switch fabric mezzanine cards from Mercury Computer Systems Inc. offer RapidIO interface support, providing bandwidth and memory needed for high-speed signal and image processing applications.

A growing number of systems are using Serial RapidIO to link multiple boxes into a single, cohesive system that communicates over fiber-optic links. The Mercury modules bring switch fabric interconnects to the existing PCI bus interface, supporting high-speed differential signals for fabric communication.

Mercury's XMC family consists of the Sensor I/O card, which provides a direct interface into a RapidIO switch fabric for sensor input. A pair of memory daughtercards buffer the data streams. These XMC modules augment a communication board that is already being used in multi-chassis RapidIO systems.

The Sensor I/O XMC daughtercard enables low-latency processing of data streaming input directly from sensors. It implements the Serial Front Panel Data Port protocol, offering two full-duplex channels that run at 2.5 Gbit/sec over fiber-optic cables. Each channel can be programmed for data distribution without host intervention, freeing the CPU for other tasks. The interface can sense input data stream signals that indicate sensor mode changes, routing data appropriately to different processors or endpoints on the RapidIO fabric.

The memory cards house either 2 or 4 Gbytes of DDR, offering a large input or output buffer to optimize data streaming. The 266 MHz DDR memory provides full-duplex data rates up to 622 Mbyte/sec in Mercury's processing systems.

The RapidIO interface includes a DMA engine for broadcast, command chaining, and corner turning. Pricing for the multi-chassis Serial RapidIO systems, which are shipping now, starts at $14,500 for the RapidIO XMC cards.

Mercury Computer Systems

How to Backlight an LCD

How to Backlight an LCD

Power Trip: Power requirements for proper operation of the cold cathode fluorescent (CCF) tube that backlights a liquid crystal display (LCD).

Cold cathode fluorescent (CCF) tubes, the light sources used for backlighting the latest liquid crystal display (LCD) modules, require careful engineering to provide the performance and service life users expect. The power requirements for the LCDs themselves-which are used for flat panel TVs, computers, medical equipment, aircraft instrumentation, and even gas pumps-are reasonably straightforward since they use standard dc supply voltages, such as 5 or 12V. But the LCDs are transmissive and require a built-in light source transmitted from the rear of the display to read them.

Most LCDs use cold cathode fluorescent (CCF) tubes to backlight the display. These tubes are not unlike the fluorescent tubes used for office building lighting, just smaller in size. These narrow-diameter tubes are very bright and can be configured as single, double, or L-shaped edge lights.

Matching Power Matters

The CCF tube ultimately determines the readability of the display. Matching the power of the inverter to the tube is essential to a successful design, as mismatching can reduce life and even cause a catastrophic failure "The whole reliability is really dependent upon how long and how well that tube lasts," says John Peterson, president, Endicott Research Group, a maker of dc-ac inverters for powering backlit flat panel displays.

The starting or applied ac voltage required to ignite the gas in the tube is a shocking specification. A fluorescent tube may require 1,500V ac to start and then 700V ac to operate. If the minimum starting voltage is not provided, the tube will not start. The dc-ac inverter is a constant current source so an excess voltage cannot occur. With most of today's electronic designs, engineers work with low dc voltages. Packaging, creepage, and clearance distances are among the design considerations.

The minimum starting voltage can change under various circumstances with starting temperature being one of the more critical factors. "Old and cold" are critical terms, according to Bryon Cole, ERG's regional sales manager who has worked on many customer applications. When the lamp is new it may take considerably less voltage to start, but with age the voltage requirements can increase producing a worst-case scenario.

The inverter must have sufficient voltage to handle the voltage drop that could occur between the inverter and the tube. This is not trivial, since the operating frequency of the lamps is 40 to 50 kHz, and stray capacitance at these frequencies can significantly reduce the voltage from the inverter.

The impedance of a typical 2.5W, 6-inch CCF tube is 50,000 to 70,000V. Both voltmeters and oscilloscopes can load the output if they were used without considering their effect on the measurement. This means that a detailed analysis must be performed to avoid unexpected voltage drops. Sufficient margin is factored into the inverter's design under normal circumstances but also requires consideration by the user to avoid extreme cases. In many instances a bit of help from the high voltage supply experts is required to validate the layout of the boards in the application.

Engineers at ERG treat any problem in the design stage as an application issue. They identify stray capacitance as a cause of early failures 90 percent of the time. The capacitance can be from misplaced metal, wires too long, and, in general, problems for high voltage that are not problems for low-voltage designs.

Constant Current: Endicott Research Group's DMA dc-ac inverter provides up to 12W for powering two CCF tubes. The two-transistor inverter is essentially a constant current ac source.

Efficiency Expert: An external pulse width modulated (PWM) control signal to the inverter (usually less than 1 kHz) controls the brightness of the CCF tube and provides efficient operation under dimming conditions.

Effeciency is Also the Key

Efficiency is another issue requiring the output current to precisely match the display's specification. Overdriving the display can produce very good image in the short term but the overall life is compromised. In some cases this meets the overall design objectives but in most cases reduced operating life is not acceptable.

For example, a Sharp 10.4-inch display specification provides a minimum life of 50,000 hrs with 6 mA but this drops to only 30,000 hrs if the current is 7 mA-just 1 mA higher. Complicating the issue, the current and frequencies measurements are very difficult since most customers do not have equipment to measure 5 mArms at 40 kHz. Using specially designed current probes and D-A converters, ERG validates that a particular inverter is a good match for a specific CCF tube.

No Strays: Testing the dc-ac inverter's no-load starting voltage requires minimizing stray capacitance and any external loading that would reduce the inverter's output.

Their test uses a non-contact current probe where the wiring is run through a transformer in the primary. The transformer generates a small voltage that is read by an oscilloscope, the signal is chopped into 512 pieces, a D-A conversion is performed, and the rms value is calculated. This allows current measurements without contacting the device since the contact would add stray capacitance and distort the reading. The inverter's circuit is designed to produce 5 mA so the measurement validates that this is performing properly in the application.

Another important design factor is observing that the waveform's distortion to minimize electromagnetic interference (EMI). The dc-ac inverter produces a pure sine wave but distortion occurs due to dynamics in the CCF tube. The current measurement also identifies if unacceptable distortion is present. Analyzing the pieces for the waveform has improved as the PC's performance has improved. Today ERG can compare point by point to a perfect sine wave at the appropriate frequency and generate a distortion factor so customers know in advance that their inverter matches the CCF tube requirements in their display.

Analyze This: The waveform (typical shown) and analysis of the output of the dc-ac inverter reveals both the critical current rating and the potential distortion.

Reach Contributing Editor Randy Frank at [email protected].

Web Resources
//Check out the links below for more info on a comprehensive range of inverters for powering CCFL-backlit LCDs.//

Endicott Research Group's dc-ac converters
Applied Concept's AC 3 series low-profile inverters
Endicott Research Group's white paper titled Design Issues in the Selection of Backlight Inverters
JKL Components Corporation CCFL inverters at
Kyocera inverters
Taiyo Yuden's inverters with 5 to 20 Vdc input voltage handling a variety of starting voltages
TDK inverters and an extensive list of inverters from various manufacturers cross-referenced for displays
Microsemi Modules and ICs for CCFL

Ask the Search Engineer

Ask the Search Engineer

RF modems . . .Threaded modems . . .Braking mechanisms . . .

Dear Search Engineer: I'm required to transmit information using RF. The minimum and maximum frequency of the pulses are 3 Hz and 20 Hz. The distance between the transmitter and the receiver is a maximum of 1m. How should I go about it? -V.I. in U.K.

Dear V.I.: There are standard interfaces available that work as "RF modem" (i.e., can be connected to the RS232 port of the user's board). On the other side, there is a connection to the RF antenna, with the same arrangement at the other end. Such RF modems commonly use an SOC, such as SiRF ( In your application, you have a signal that equals pulses of 3-20 Hz, so you might build a simple circuit using a SiRF chip and an RF antenna.

Dear Search Engineer: We are looking for a process to make 2 x 3/4 inch through-hole x 3/16-inch thick rubber or urethane washers with metal impregnation for weight characteristics. We would prefer corrosion resistance of impregnating the metal. Is there such a process? -M.G., DN reader

Dear M.G.: To produce clean holes through metal-impregnated rubber urethane, try a water-jet cutter with a ruby orifice to restrict the stream and clean up the overspray. This will allow you to lay a sheet of the material on the platen and cut multiple units.

Dear Search Engineer: Often when repairing a piece of equipment, you run across a threaded fastener of unknown specification. You can get the measurements of it, but they may not match anything familiar. Is there some resource (website, printed table, book, etc.) that consolidates various thread specifications from around the world? The idea is that you could enter a thread parameter (pitch, major diameter, etc.) and get a list of matching available fasteners. -R.L., DN reader

Dear R.L.: There is a book that describes the threads of the world, called Guide to World Screw Threads, published by Industrial Press Inc. Check it out at

Dear Search Engineer: I am looking for a solution to this application: a machine runs fom 200 to 800 cycles per minute. When I press "stop," a braking mechanism comes in to stop the machine. The machine stops at a different position, depending on the speed; that means that at 200 cycles per minute, the machine stops at 1:00, and at 800 cycles per minute, it stops at 7:00. I can tabulate these various stopping positions at the various speeds. These stopping positions are consistent at the various speeds. I would like to stop the machine, regardless of the running speeds, at a fixed position for me to decide. Feedback is via a rotary encoder. -M.K., Singapore

Dear M.K.: Try inserting an adjustable time-delay relay or circuit between the "stop" button and the braking device. By adjustment of the time delay, you should be able to pre-set, or at least make adjustments on the fly to engage the defined stop point at various operating speeds.

Thermal System

Thermal System

Degree Controls Inc. ( has introduced the PRONTOflowTM line of off-the-shelf, programmable thermal controllers and fan trays for applications such as power and acoustics. The PRONTOflow controller is configured to accept 36 to 60V dc. It can provide regulated voltage to a system of up to nine fans. In addition, both I2C and RS232 protocols allow full communication to a host system. Other features include various choices of controller cards.

Electronics Catalog Gets New Look

Electronics Catalog Gets New Look

With the exception of Victoria's Secret, most catalog covers have all the allure of steam tables in compelling engineers to open them up. But Rob Birse, marketing manager for electronics catalog distributor Allied, wanted to change that "Okay, it's a catalog. I'll put it on the shelf until I need it" mentality. "Obviously our catalog is our main sales tool, and we felt we needed to create a bigger impact when it arrives on our customers' desks," he explains. By making the cover rich with detail, we felt we would achieve a higher degree of curiosity and get him or her into the catalog." When we interviewed Birse in August, before the new catalog was unveiled, he was being coy about any details on the cover design, only hinting that it would mimic a consumer magazine like Men's Health, which uses life-style photography to attract and inspire readers. He was also quick to point out that the cover isn't the only transformation of Allied's 2003/2004 catalog. In addition to more color photographs of product, he noted that the index has improved, claiming that it will now be ten times easier for an engineer to find the right product. The catalog also contains more data than in the past, which is only the start of what Birse promises to be an explosion in the amount of technical data Allied's catalog will feature.

CMOS Sensor

CMOS Sensor

OmniVision Technologies ( has unveiled its OV5610 CMOS image sensor with 5 megapixels and optical format (footprint) of 1 or 1.8 inches. Targeting the high-end camera market, OV5610 also features an on-chip 10-bit A/D converter capable of operating at up to four frames per second (fps) in full resolution.