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Articles from 2004 In November


New Products for Packaging Machinery

New Products for Packaging Machinery

Packaging is a booming technology, and new motion control products are continually being introduced to make it easier for design engineers to get the performance they want on packaging lines. Among the latest product introductions: a new gear motor, a new bipolar driver/controller, and a new drive nut.

Midwest Motion Products (www.midwestmotion.com) introduced a 12-volt DC gear motor for packaging applications. It's 2.8 inches in diameter and 5.6 inches long, with an 80 mm-square gearbox. The output shaft is 10 mm in diameter.

The motor has an 18:1 gear ratio and shaft output speed of 160 rpm. It's rated for 26 in lbs of continuous torque at 3.9 amps of current, and is capable of 70 in lbs of peak torque.

Meanwhile, RMS Technologies (www.rmsmotion.com) unveiled the R101 bipolar driver/controller. Itg's capable of output current from 0.2 to 2.5 amps/phase, with step resolution from full, .50, .25, and 1/8.

And, Amacoil (www.amacoil.com) announced the Model RS4 drive nut for backlash-free linear motion. The drive nut is available in seven sizes, and the nut can be used in vertical or horizontal applications. The shaft rotational speeds can be up to 10,000 rpm. Linear travel speeds range from 0.5 ft/second up to 4.0 ft/second. Axial thrust ranges from 22 lbs to 449 lbs.

The company installs Uhing rolling-ring bearings under pressure in the drive. There is a constant single point of contact between bearings and drive shaft. The result, the company says, is zero play when the shaft rotates.

Midwest Motion's 12V DC gear Motor is rated for 26 in lbs of continuous torque at 3.9A.

High-flow air valves simplify router design

High-flow air valves simplify router design

Precision PCB Products used the VM10 valves to simplify the design and reduces costs on its new Final Touch 101 printed circuit board router.

Using a compact, high-flow pneumatic valve manifold, engineers have simplified the design of a new printed circuit board routing machine. The machine, designed by engineers at Precision PCB Products (San Clemente, CA), used pneumatics instead of electric motors as a means of holding printed circuit boards in place during the so-called "de-panelization" process, in which small circuit boards are cut from large electronic panels. By doing so, engineers said the OEM was able to deliver a smaller, tidier machine.

"We were able to put all the pneumatics in a very small package," notes Mike Gibbons, district sales manager for Norgren, Inc. (Los Angeles, CA), which supplied the pneumatic components. "The valve stack that we used weighs only four or five pounds." Gibbons adds that the six-valve stack measures a mere 5.25 inches long, making it more than 20 percent shorter than a comparable stack using a more traditional design.

In the routing application, OEM engineers employed the compact valve stack as a means of controlling and delivering pressurized air to tiny air cylinders that hold the printed circuit boards in place during the routing process. They say that the ability to eliminate inches in applications such as those, as well as in other tightly packaged applications, such as end-of-arm robotics and pick-and-place machinery, is critical.

The company claims that the key to the creation of the smaller, lighter stack is twofold: Norgren engineers incorporated small, high-flow valves; and they employed a unique manifold design that combines the so-called "sub-base" with the valves in a single block.

"Traditionally, you'd have a pneumatic sub-base and an electrical sub-base, and you'd screw the valves on top," says Brady Webb, valves business development manager for Norgren, Inc. (Elk Grove Village, IL). "But by combining the sub-base and the valve into a single block, we cleaned up the flow path and maximized air flow through the valve." Indeed, Norgren's 10-mm-wide VM10 valves used in the application offer a Cv of 0.440 (440 liters/min), approximately two to three times more than that of competing pneumatic valves of similar size.

Norgren engineers attribute the higher flow capabilities to a hinged design that connects the sub-base to the valves. The hinge, they say, eliminates the need for tie rods, which reportedly take up space and contort the flow path, which in turn lowers the flow rate. In contrast, Norgren engineers say that by eliminating the tie rods, they've cleaned up the valve's internal configuration.

"The internal pathways that go to the pressure ports and outlet ports on this valve are very wide open," Gibbons says. "It's a direct shot through the valve, so you don't get the turbulence and other issues that can cause flow to drop off."

To come close to the 440-liter/min flow rate with a more traditional pneumatic valve design, Norgren engineers say they would have needed 18-mm-wide valves, instead of the 10-mm-wide versions that they used.
Moreover, the configuration simplified assembly of the PCB routing machine because it allowed the valves to simply snap onto a standard DIN (Deutsches Insitut fur Normung eV) rail, thereby speeding manufacturing.

The high flow rate of Norgren's V10 valves, enabled engineers to employ 10-mm-wide valves, instead of 18-mm designs.

During operation of the routing machine, the VM10 valves deliver air at three different pressures: 15 psi for normal operation of the "pressure feet" that hold the PC boards in place; 60 psi for situations calling for tighter pressure-foot clamping; and 80 psi for other pneumatic functions, such as opening and closing the chuck inside the router's spindle.

By choosing pneumatics over electrics to accomplish all that, Norgren engineers claim they helped make the machine smaller and less costly. "If you do this electrically, then you're dealing with power amplifiers and linear motors or lead screws, which add up in cost," Gibbons concludes. "Pneumatics are the most economical way to go for a project like this."

Electrically Actuated Workstations Relieve Muscle Strain

Electrically Actuated Workstations Relieve Muscle Strain

Fresh research from a prominent ergonomics expert verifies what most of us instinctively knew: changing positions relieves the strains of cubicle life.

Professor Alan Hedge of Cornell University's Human Factors and Ergonomics Research Laboratory studied 53 office professionals who spend most of their day in front of computers, including Intel design engineers in Santa Clara, CA, and CNA insurance workers in Chicago. Participants were asked to compare their experiences working at least one month at a fixed-height workstation with a similar period at electric height-adjustable workstations. Among the chief findings:

* Participants reported nearly 20 percent less musculosketal discomfort with the electric stations, which allowed them to raise work surfaces from a sitting position to a standing position in a few seconds.

* In terms of the perceived impact of workstations on productivity, nearly 58 percent of the workers said the adjustable stations were a clear plus, compared to only 20 percent citing productivity gains with fixed-height stations.

* And in terms of overall satisfaction, nearly two thirds stated a definite preference for the electric stations. Only one individual favored the fixed station.

Stated one worker: "As soon as I started to get any pain, I adjusted the table height, and the pain went away."

And from another participant: "The varying heights definitely helped avoid repetitive stress in a big way."

Three of the Intel engineers were so happy with being able to work sitting or standing that they refused to relinquish their adjustable stations at the end of the study.

Playing Catch-Up: Professor Alan Hedge of Cornell says the U.S. lags behind Europe and Australia in introducing adjustable workstations.

Consistent with past research
The results did not surprise Professor Hedge, who cites a history of ergonomic studies showing that "the best position is the next position." But he adds that it is very difficult to vary positions at work when you can't adjust the height of the workstation. Moreover, the study showed that the employees preferred to stand while working 20 percent of the day.

However, adjustable stations that rely on hand cranks don't do the job, says Hedge. "They aren't as easy to use," he told Design News, "plus the loads can be quite heavy, especially with the large monitors that many engineers use."

Earnest Ray, the site ergonomist at Intel's Santa Clara headquarters, adds that being able to stand and work caters to the habits of engineering teams, who frequently meet for impromptu sessions during the day to review each other's designs. "Our cubes are small-about 8 ft by 9 ft-and it can be uncomfortable when two or three engineers must lean over to view a design on a monitor."

The adjustable workstations used in the Cornell study are manufactured by WorkRite Ergonomics. Petaluma, CA (www.workriteergo.com) and incorporate Desklift DB4 electric actuators from LINAK (www.linak-us.com), a Danish company with U.S. Offices in Louisville, Ky.

Derek Manz, a technical services manager for LINAK, notes that the actuator is compact-just 22 inches when installed-yet raises a work surface a total distance of 26.6 inches in as little as 15 seconds. Key components include: a quiet, 18V DC electric motor and a dual-sprocket chain drive system. In workstation setups where more than one actuator is used to lift larger surfaces, LINAK's CBD4 control box automatically aligns each desk column's height to provide an even work surface, based on positioning feedback from hall sensors attached to the actuator motors.

"The LINAK actuators give us the quality we need at the right price point," says Todd Hauge, WorkRite president, who sees growing demand for electric adjustable workstations, despite the 25-percent price premium such stations demand versus hand-cranked adjustable stations and the 40-percent premium versus fixed stations. "Engineers are part of the creative class who create the value in our economy, and it makes sense for companies to invest in their productivity," says Hauge.

Manz agrees that large companies in particular-especially those building new facilities--increasingly choose electric adjustable workstations. At his location, notes Intel ergonomist Ray, engineers are issued these workstations on a case-by-case basis, typically related to health and productivity reasons. But given the proven benefits of the electric stations, Rays adds: "I usually support their requests."

CPLDs Move to Chip Scale Packaging

CPLDs Move to Chip Scale Packaging

Space Trimmed: CoolRunner CPLDs measure 5 x 5 mm to 7 x 7 mm, taking little board space, not consuming much power.

Consumer demand for small equipment with long battery life seems unquenchable, so the need for compact, low-power devices continues unabated. Xilinx Inc. is responding with low-power CPLDs that provide chip scale packaging that trims space requirements while matching the prices of larger quad flat packs.

The San Jose, CA, supplier of complex programmable logic devices is expanding its CoolRunner-II family with chips that have an extra I/O bank that can be used to support voltage level translation and device interfacing.

Two new chips, the XC2C32A and XC2C64Aa, offer smaller packaging than discrete logic devices now used for level shifting, while also providing the potential to implement additional logic functions using extra programmable gates.

The parts employ micro lead frame packaging, which provides the size of chip scale packaging at lower costs than discrete parts. The 32-cell version comes in a 32-pin version that measures 5 x 5 mm, while the 48-lead, 64-cell part measures 7 x 7 mm. The 32 and 64 macrocell parts offer 21 and 37 I/O lines respectively.

The CoolRunner line is designed for low-power applications, using the company's proprietary RealDigital technology. The parts draw only 14 muA in the standby mode.

Voltage shifting can be implemented using standard I/O pin configurations, so programming files don't have to be altered. If these translations don't require all the programmable cells that are available, cells can be used for additional functions. Though voltage translation is a key target application, the parts can be used as extensions of standard products or ASICs. A clock doubler and clock divider enable the chips to run in many systems.

The digital cores run at up to 385 MHz. Pricing for the parts, which are available in lead-free packages, start at 85 cents. The parts can be programmed with the company's ISE software. Additional members of the line have up to 256 macrocells.

Xilinx Inc. http://rbi.ims.ca/3859-576

Blood Test

Blood Test

Present Position: Professor of Chemistry, Worcester Polytechnic Institute

Degrees: B.Sc., M.Sc., Chemistry, Brock Univ.; Ph.D., Chemistry, Queen's Univ.

How are you developing optical sensors for whole blood analysis? We design a molecule that will bind to a particular analyte, or blood component, without attracting other components. We next carry out detailed computational analysis called molecular modeling and molecular dynamics, and then devise schemes for synthesizing the molecule. We test its response to analytes, and incorporate it into a sensor.

How is the blood then analyzed? Some of that molecule can emit fluorescence when it is probed with UV light. Under conditions when the analyte is not bound to the molecule, the fluorescence emission is switched off by a process called electron transfer. When the ion is bound to the molecule, its electrostatic field disrupts the electron transfer quenching and the fluorescence is switched on. Essentially, we create an 'off-on' fluorescence switch.

How is whole blood currently analyzed? An electrochemical approach uses ion selective electrodes (ISE) to provide a nearly instantaneous potentiometric response to the analyte ion.

Why switch to optical sensors then? The downside to electrochemical sensors is that there are a lot of calibration steps that need to be performed for each sample. Bulk optical sensors are potentially cheaper to manufacture and use, though the measurement is longer (at least 30 sec).

Any other applications? Military and homeland security; many chemicals are similar in structure to chemical warfare structures but are completely harmless, so we need sensors that will respond only where appropriate.

For more info on this research, visit http://rbi.ims.ca/3859-533 ; and for McGimpsey's further research into untethered healthcare, visit http://rbi.ims.ca/3859-534 . Contact McGimpsey at [email protected] .

Electronics

Electronics

SENSORS

For off-road mobile machines

The company's family of inductive proximity sensors reportedly feature 316 stainless steel housings and are rated IP69K to ensure a high level of protection against liquid ingress. With an operating range of -40 to 185F, the products are designed for mobile machines used in off-road applications. They can tolerate harsh outdoor conditions and extreme temperature fluctuation, according to the company. Families include 12-, 18-, and 30-mm diameter sensors, flush and non-flush mountable. ifm efectorhttp://rbi.ims.ca/3859-577

PLUG CONNECTORS

For industrial uses

The Heavycon-Advance rectangular plug connector housing, suitable for applications in which the connector will be plugged and unplugged, is now available with bayonet locking. Constructed from aluminum die cast, the housings are available in three finishes: standard, which is good for rugged requirements like automotive and machine industries; corrosion-resistant, which is good for applications where chemicals are involved; and EMC, which is good for shielding protection. The Heavycon-Advance housings provide more wiring space than Heavycon housings, according to the company. Phoenix Contacthttp://rbi.ims.ca/3859-578

RELAYS

Solid-state

Designed for switching medium- to high-power dc loads, the Series S20DC30 and Series S20DC100 commercial dc solid-state relays reportedly feature the latest-generation MOSFET technology and an innovative isolated driver to ensure fast power turn-on and turn-off. The S20DC30 offers output to 30A at 200V dc, while the Series S20DC100 offers output to 100A at 200V dc. Both can also be used in an H-Bridge configuration for reversing, according to the company. Other suitable applications also include heating control, motor control, UPS, automotive, back-up power systems, and stepper motor drivers, among others. Teledyne Relayshttp://rbi.ims.ca/3859-579

E8 POWER PROBE

Handheld

The Comet 1K Power Probe, a handheld laser power measurement probe designed to measure low to medium laser power, is accurate, economical, and easy to use. The probe can be used to measure laser power from 20W to 1 KW and it has a highly sophisticated algorithm to correct for the starting temperature of the puck so that an accurate reading is obtained every time. Additional features include a swivel mount that rotates more or less than 90 degrees, a two-by-eight character LCD, and the ability to store the history of the last three readings. Ophir Optronics Inc.http://rbi.ims.ca/3859-580

LEVER SWITCH

Toggle can be locked

The 100 series K locking lever switch reportedly allows the toggle to be locked in any of three positions to prevent unintentional actuation. It is designed for rugged environments, and the panel-mounted switch is intended for wide application in instrumentation, test circuits, and industrial control equipment. It features plated brass and stainless steel construction, and has a minimum electrical and mechanical life of 40,000 cycles. E-Switchhttp://rbi.ims.ca/3859-581

CABINETS

Earthquake-proof

The company's range of customizable seismic Zone 4 cabinets is designed to offer high protection against shock and vibration. They are comprised of a rugged, cold roll steel frame with reinforced structural steel corner angles. They are reportedly suitable for heavy duty, indoor applications in the telecom, security, and defense industries. Schroffhttp://rbi.ims.ca/3859-582

RECTIFIER

High-voltage, high-current

Combining 100V reverse voltage and 60A forward current capabilities, the MBR6010CT rectifiers present in the TO-220AB package are intended for secondary rectification of ac-to-dc and dc-to-dc converters, and for freewheeling and polarity protection in power supplies. These power supplies can be found in desktop and notebook PCs, servers, telecommunications exchanges, HDTV equipment, and other systems incorporating high-power switchmode power supplies. Good for 100 to 300W applications, the rectifiers feature a low forward voltage of 0.64V, according to the company. Vishay Intertechnology Inc.http://rbi.ims.ca/3859-583

TOUCH PROBE

Compact in size

Intended for machines that are carrying out repeated setup and inspection procedures, and have limited working space, the TS 440 model of 3D touch trigger probes from HEIDENHAIN is extremely small and is offered in as small a size as 0.49 x 63 mm. Offering 360 degrees of transmission, the TS 440 can be used on the iTNC 530 control and higher in conjunction with HEIDENHAIN's transceivers. The 3D touch probes are suitable for quick workpiece alignment as well as for automated workpiece measurement on the machine. Heidenhainhttp://rbi.ims.ca/3859-584

TRANSDUCERS

Meet audio alert requirements

Models TRIE-23xx and TRIE-26xx transducers reportedly provide audio alerts that meet the new medical equipment requirements. The TRIE-26xx audio alert is offered in rated voltages of 6, 12, and 24V dc at 40 mA for each rated voltage. The TRIE-23xx EM buzzer is offered in both panel and PC mount in rated voltages of 1.5, 3, 6, 9, 12, and 24V dc at 25 mA. Transducers USAhttp://rbi.ims.ca/3859-585

LIGHT PIPE

For board-mounted push-button switches

Designed to operate with board-mounted push-button switches, the PBLP Series of light pipe reportedly allows non-lighted switch models to perform the same function as similarly mounted lighted push-button switch types when used in conjunction with surface-mounted LED chip sets. The product reportedly offers an integral prism design within the light pipe, directing the surface-mounted LED light down the center of the light pipe. Applications include medical devices, professional recording consoles, and test and measurement instruments. Bivar Inc.http://rbi.ims.ca/3859-586

MICROPHONE

Polarized pressure

Model 377A51, a .25-inch, externally polarized pressure microphone for extremely high-level decibel measurements, has a flat pressure-frequency response from 10 Hz to 20 kHz. Made of stainless steel, the microphone measures sound pressure levels up to 192 dB, and meets IEC and ANSI standards. Applications include acoustic testing of airbags, aircraft and rockets, gun blast, and other high decibel uses. The microphone operates via a 200V power supply. PCB Piezoelectronicshttp://rbi.ims.ca/3859-587

PUSH-BUTTON SWITCH

Right-angle, illuminated

Designed to eliminate the need for separate LED and light pipe on the PC board, the right-angle C&K ELUM(TM) illuminated push-button switch from ITT industries, Cannon, has an LED built right into its actuator. The switches also feature a 6 mm profile and are available in through-hole and surface-mount configurations. The SPDT contact can withstand 20 mV to 50V dc. The switch has a robust design, which makes panel building, instrumentation, and other applications easier to implement. Colored LED colors and customized caps are also available. ITT Industries, Cannonhttp://rbi.ims.ca/3859-588

Stop Burning Money: Forget Prevailing Wisdom

Stop Burning Money: Forget Prevailing Wisdom

Integrated circuit (IC) technology provides added features and improvements with each advancement in processing and design methodology. Since available board space can be costly and, in some instances, non-existent in next generation designs, taking advantage of the higher integration in the latest ICs to eliminate components is normally an excellent design strategy. A potential downside comes when all the features of the IC are not required for an application. Each added feature normally requires more pinouts, which in turn means a larger, more expensive package.

An IC with just the right amount of integration can use a package with fewer pins and provide a significant reduction in cost for both the product and a significant savings in board space. An example of this approach is a microcontroller (MCU) that fits into a six-pin SOT-23-a semiconductor package initially developed for a single discrete transistor. Microcontroller packaging has been reduced from14 pins to eight pins for the more cost-effective, limited function MCUs and the eight-pin packages have continuously shrunk during the past decade. A SOT-23 six-pin MCU such as one from Microchip's Pic10F family is packaged in a 2.8 x 2.95 mm package that occupies only 28 percent of the footprint of a 6.01 x 4.89-mm SOIC-8 package that was state of the art just a few years ago. The MCU still provides functions such as:

  • Eight special function hardware registers

  • 4 MHz precision internal oscillator

  • 3 I/O pins with individual direction control, one input-only pin

  • High-current sink/source for direct LED drive

  • 8-bit real-time clock/counter (TMR0) with 8-bit programmable prescaler

  • One comparator

Among other possibilities, these functions allow the chip to provide a soft-start controller for switching power supplies with only two additional components-a hefty cost savings.

Getting the heat out of power MOSFETs frequently involves a heatsink attached to a back-plate. To stop the baseplate from getting electrically hot, an electrical isolation pad with good thermal conductance, such as Bergquist's Sil-Pad, is used between the MOSFETs and the heatsink. The problem with this approach is that attaching the leaded TO-220 power MOSFETs to a printed circuit (pc) board requires hand soldering of the leads-a processing cost adder that can be significant.

An alternative solution uses a metal-backed board, such as Bergquist's Thermal Clad Insulated Metal Substrate (IMS) material mounted to the back plate and stand-offs to connect to the printed circuit board. (See the comparison in the brown box at left.)

The thermal performance of both methods is about the same. The MOSFET is the same as the initial case, but in a surface mount version. By automating the assembly process, an estimated cost savings of $0.50 labor per heatsink assembly is expected. For units with several heatsink assemblies there is a significant payoff. For example, with six of these units in a brushless dc motor and an annual volume of 10,000 units, the cost savings can be $0.50 x 6 x 10,000 =$30,000. The tradeoff for this approach is the standoffs also carry high current. If this isn't a problem, take the money and run with this one.

Connection: Using a standoff to electrically connect the surface-mount MOSFETs on an IMS board to the rest of the circuitry on the PC board reduces cost for both the components and assembly.
Smaller, smaller, smaller: Microcontroller packages shrink with each new silicon process improvement, allowing the same or more functionality to be available in increasingly smaller footprints. Eliminating two pins does require sacrificing some performance, but for many designs there is still more than enough MCU capability. Those applications are ideal candidates for cost savings.
T-Clad $3.11
Total $3.11
MOSFETs on Heatsink
Heatsink $1.55
Screws (2) @ $0.05 $0.10
Spring clip $0.05
Sil-Pad 10 pcs @ $0.21 $2.10
Total $3.80

Ready or Not, Here Comes Digital

Ready or Not, Here Comes Digital

Good Hybrid: A reference design for powering a fluorescent light using Fairchild Semiconductor's FMS7401 requires only three ICs and provides medium to high performance with programmability and a high degree of flexibility.

The first Digital Power Forum (DPF), Sept. 13-15 in San Jose, CA, created a compelling event to announce new products for companies that had been working on digital power control. At the DPF, Primarion, a mixed signal IC company that is addressing the transition from analog power to digital power, announced a digital control chipset for core power regulation in high-performance computing, graphics, and networking applications. The processors in these systems have operating voltages between 1.1 and 1.3V, and require supply regulation of 40 mV. With increasingly lower voltages and higher currents forecast for high-performance Intel and AMD processors, new design approaches using digital technology are expected to play a critical role for providing power for these logic chips.

Versatile integration

Primarion's PX3535 digital multiphase controller manages two to six phases, and the PX3536 handles from two to four phases. The multiphase approach is also used in analog designs to distribute the total current and minimize stress on individual components, such as MOSFETs and inductors. Integrated analog-to-digital converters (ADC) in the PX3535 and PX3536 transition voltage, current, and temperature to the digital domain for improved control. All of the internal registers for the digital controller are accessible through an industry standard I2C serial bus for customizing the protection features.

Operating at frequencies up to 1 MHz, the PX3520 power stage portion of the chipset integrates the low- and high-side MOSFET drivers and a control (P-Channel) MOSFET into a chip scale package delivering up to 30A per phase. Process and temperature independent loss less current sensing designed in the chip allows accurate loadlines and overcurrent protection. Integrated temperature sensing works in conjunction with the PX3535 controller, providing accurate programmable thermal shutdown protection.

The chipset has demonstrated 85 percent efficiency at 120A load current (four-phase) in a 1U (1 x 4 inches) voltage regulator module using a 2,000 muF capacitor. At 105A, the peak-to-peak ripple voltage was only 14.4 mV. The combination reportedly produces the highest power density for server and workstation buck regulators.

"These are some of the first announcements," says Jeff Shepard, president of Darnell Group and organizer of the DPF. "Those companies that did not see digital power coming are starting to feel they could be left behind."

The digital multiphase power ICs that are made by Primarion are second-sourced by Intersil to accelerate acceptance and adoption of the digital multiphase architecture. Intersil's products are the ISL6591 digital multiphase controller and ISL6597 integrated power stage.

More digital power solutions

Other companies showing digital power solutions at the DPF included Texas Instruments (TI), ST Microelectronics (STM), Fairchild Semiconductor, and Power-One.

TI showed several digital solutions including a digitally assisted power supply design made possible by an advanced analog controller that is not yet introduced. This approach, dubbed a DPPA interface for digital power partitioning architecture, combines the microcontroller (MCU) and a digital-compatible analog controller that adds enhanced control features. The analog controller drives the power stage and receives bias feedback information from the power stage for the MCU. The MCU receives temperature voltage and current limit flag information, and communicates with external circuitry while clocking the analog controller. Using an SMBus for communication, digital aspects that can be implemented include programming, configuration, adjustments, test and calibration, and remote status reporting and polling.

STM presented a monolithic IC design using asynchronous pulse width modulated (PWM) logic for digitally controlling voltage regulator modules. The design avoids the digital PWM approach that typically requires high sampling frequency and high resolution in both analog-to-digital and digital-to-analog converters to reduce quantization effects that include noise and higher output ripple. Instead, a PWM signal is generated by comparing the load current, Il, and output voltage, Vout, with two reference levels. The reference levels are generated by the digital controller and managed by a control algorithm. Integral digital to analog converters (DACs) provide analog voltage and current levels for the integrated comparators.

Some companies took advantage of the digital situation to reiterate previously introduced digital power solutions.

Multi-Approach: Primarion's digital power chip set that consists of a PX3535 digital multiphase controller and PX3520 power stage (top and back) can provide 30A per phase in a small form factor.

Fairchild discussed their FMS7401L, a hybrid digital power controller that integrates several analog functions with an 8-bit microcontroller core. The combination provides ease of analog interface with digital programmability. The FMS7401 has typical MCU peripherals including 1 kbyte of on-board code EEPROM, 64-byte data EEPROM, and 64-byte SRAM. Application-specific features for digital power control are a fast 12-bit PWM timer with dead time control and half-bridge output drive, and a 5-Ch 8-bit analog to digital converter. The analog portion of the hybrid includes an uncommitted amplifier, temperature sensors, auto-zero amplifier, and current source for interfacing to optocouplers for isolated power supplies. Fairchild's comparison of analog, digital (based on DSP technology), and the hybrid approach shows the hybrid to be a good compromise.

Power-One displayed and discussed their Z-One Digital Intermediate Bus Architecture (IBA) that provides a 50-percent reduction in printed circuit board (PCB) space, 20-percent cost savings, a 90-percent decrease in components, and reduced power-system development time.

The logistic and performance improvements from the digital IBA result from two companion chips: a Digital Power Manager (DPM) and a Z-POL converter. A Z-One Digital System has a special graphical user interface (GUI) to easily set Z-POL parameters including output voltage, sequencing, tracking, and protection type.

For those who want to see what happens next, the second Digital Power Forum is already scheduled for Oct. 3-5, 2005, in Boston.

Analog Digital Hybrid
Cost low high medium
Performance low-medium high medium-high
Flexibility low high high
Programmability low medium-high high
IBA with External Power Management Z-One Digital IBA
No. of components 200+ 9
No. of traces 6,000+ 76
PCB space (inch2) 10 4.4
Development time 2 weeks 2 days
Total cost $150+ $120
Power management Limited Unlimited


Power Control Resources
//For more information on the latest digital power offerings, visit the following websites//

Digital Power Forum:
http://rbi.ims.ca/3859-511
Primarion PX3535, PX3536, PX3520:
http://rbi.ims.ca/3859-512
Intersil ISL6591, ISL6597:
http://rbi.ims.ca/3859-513
Texas Instruments:
http://rbi.ims.ca/3859-514
ST Microelectronics:
http://rbi.ims.ca/3859-515
Fairchild Semiconductor:
http://rbi.ims.ca/3859-516
Power-One Z-One Digital IBA(TM):
http://rbi.ims.ca/3859-517

Report Card on Electrical Stimulation

Report Card on Electrical Stimulation

What are the basic technologies involved in functional electrical stimulation? Essentially, FES uses electrical stimulation to activate nerves and ultimately restore some function of the body that has been lost through injury or illness. For example, the Freehand system developed here at our FES Center uses an implanted electrical stimulator together with implanted electrodes to activate muscles in the hand and forearm. This enables paralyzed patients to grasp and release objects.

How is the field developing-in terms of adding new applications? Some researchers now make the distinction between neurostimulation, such as the example I just gave, and neuromodulation, which uses electrical stimulation to activate whole populations of cells. An example of the later would be deep brain stimulation, such as the implant developed by Medtronic to control tremors in Parkinson's patients.

What are some of your projects? If you go to our website (http://feswww.fes.cwru.edu), you'll see descriptions of more than 40 research and clinical programs. These include several to aid those who have suffered spinal cord injuries, such as systems that allow individuals to stand and take steps, or that relieve pressure sores, alleviate breathing problems, or control bowel or bladder functions. For the broader population, our research ranges from devices to counter sleep apnea to those that relieve shoulder pain in stroke victims or retrain muscles paralyzed as a result of stroke. Still another device under development seeks to improve vision in patients with involuntary eye movements, sometimes associated with multiple sclerosis.

Are you close to commercialization? We are constantly seeking commercial partners to bring these technologies forward. One of the big developments for our program over the past couple years has been funding assistance from the State of Ohio aimed at helping us bring more of our technology to the prototype stage where it would be of interest to commercial partners. These funds are focused particularly on systems aimed at four areas of concern: sleep apnea, pain relief, motor control in stroke victims, and urinary incontinence.

What major improvements are needed in FES systems? Certainly, we need to engineer systems that can be produced more economically. These devices also need to be more transparent and user-friendly for patients. Take the Freehand system, for example. Older versions required the patient to wear a shoulder-mounted exterior positioning sensor, which obviously was difficult for someone with paralysis to put on every day. Our latest version employs an implanted sensor array in the forearm, which is both extremely reliable and more acceptable to patients. Beyond that, rather than design systems for just one or a few applications, we are trying to develop basic FES modules that can be used in several applications. Medtronic has done an excellent job of leveraging the same basic technology in applications for pain relief, urinary incontinence, and deep brain stimulation. Ideally, we want to develop systems that would have the power supply and all sensors inside the body.

Author Information

Peckham, a Ph.D. biomedical engineer, is a former Design News Engineer of the Year. He has pioneered technologies based on functional electrical stimulation for more than 30 years.

The Case of the Errant End-Loader

The Case of the Errant End-Loader

A southern coastal city was experiencing turmoil in its sanitation department. A large end-loader had "jumped into gear," crushing a worker. He suffered broken bones and internal injuries. His suit named the loader manufacturer, the parking brake and other loader component suppliers, and an outside service contractor. I was retained to inspect the loader and reconstruct the accident.

The loader had four tires and a front-mounted, 4-cubic-yard bucket. Diesel power came through a three-speed/forward-reverse, hydraulic transmission. Its output passed through a spring-applied, air-released, drum parking brake. The parking brake applied automatically with air supply loss, or by a control knob.

Evidence suggested this scenario: Unable to start the engine, the driver called the plaintiff, a maintenance man. The plaintiff brought a battery cart, squeezed in the space between the dead loader and another loader, and hooked up jumper cables. After starting the engine, the driver set both the parking brake and a hand-throttle to a fast idle to charge the battery. While disconnecting the battery cables, the loader jumped forward and pinched the plaintiff against the adjacent loader. Only the impact of bucket against bucket stopped the loader and prevented a fatality.

The usual cast of characters, including experts, lawyers and, yes, some loafing city workers, assembled for the inspection. The city sanitation department provided us with a mechanic. At my request, the mechanic turned the keyswitch to the start position and declared the machine unable to start. The regular loader driver who was watching the inspection, stepped over to tell us he always had to "jiggle" the shift lever to find the neutral position before starting. With this cue, the mechanic proceeded to fire the engine. He set the throttle for a fast idle and, after a few moments, the shift lever, a chunky steel bar that stuck out from the instrument panel, visibly vibrated and dropped downward, engaging forward speed and causing the loader engine to jump forward.

Service information and inspection revealed about a half-dozen linkage and pivot points between the shift lever and the transmission. With the neutral-start switch up on the shift lever, linkage wear-and-tear allowed the transmission shift spool to be moved out of its neutral detent while the driver fished around to find the neutral position on the maladjusted switch. Vibration from the fast-idling engine caused the heavy shift lever to drop, slipping the transmission into forward gear. Over time, the regular loader driver just accommodated this peculiarity and never reported it for repairs. So, okay, that explained the loader jumping into gear. But why did the loader move with parking brake applied?

The mechanic then tore down the parking brake. The spring unit was in good order, but we found a linkage pin in the drum brake assembly out of position. This left only one of the two internal brake shoes working. The brake could hold the loader in second and third speed, but allowed loader movement in first gear above idle speed. I deduced that the brake was never assembled correctly during manufacture as the friction lining on one brake shoe was virtually brand new.

My opinion report stated that the outside service contractor failed to follow procedures to check parking brake performance and make the necessary corrections. The manufacturer had failed to both install the parking brake correctly and to check its performance, and had produced a negligently designed gear-shift linkage and neutral-sensing system. The engineers who designed this loader failed to grasp the function of a neutral start switch-it must be designed to sense transmission neutral, not shift lever neutral.

Before trial, the service contractor and other component manufacturers settled with the plaintiff. Called to testify at an arbitration conference with the manufacturer, I used illustrations with transparent overlays to compare the existing linkage and neutral switch on the shift lever and its wear points to a neutral switch on the transmission spool. Settlement quickly followed this conference.

Reach Myron J. Boyajian, P.E., at [email protected]. Cases presented here are drawn from his actual files.