Appliance Design October 2011

October 2011

REACHING OEM DESIGN ENGINEERS ACROSS CONSUMER AND COMMERCIAL MARKETS WORLDWIDE

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SHHHH HEY APPLIANCE...

INSIDE 14 Motors 16 Prototyping 20 Electronics 24 Controls & Sensors

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CONTENTS OCTOBER 2011 volume 59, no. 10 REACHING OEM DESIGN ENGINEERS ACROSS CONSUMER AND COMMERCIAL MARKETS WORLDWIDE

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DEPARTMENTS 4 Editorial: Is Nanotech an Environmental Concern? 6 Shipments/Forecasts 8 News Watch 28 New Products

16

31 Advertiser’s Index 32 Association Report: AHRI

14

FEATURES MOTORS 14 Whatever the domestic appliance, choosing the right bearing mount solution can pay rich dividends for those manufacturers who look to the finer details. Tolerance rings are a key component for reducing noise and vibration in electric motors.

PROTOTYPING 16 A description of the key factors – functionality, life cycle, durability, usability, and workmanship – that should define your product testing parameters.

appliance DESIGN ONLINE WEB EXTRAS WEB EXTRAS

New, Easy, Inexpensive – A Winner? AirFloss has a simple idea that should appeal to anyone who’s ever used a water-based flosser.

Energy Star Label and Smart Grid Catch a sneak peek of AD’s November article by Amanda Stevens of EPA’s ENERGY STAR program, who claims the program is keying on Smart Grid tech as the future of its label. Tax Incentives for Insulation Several U.S. lawmakers have put forth a bill that would incentivize the use of mechanical insulation to prevent energy loss in equipment such as boilers, HVAC, duct work, and hot/ cold water piping.

BLOGS

ELECTRONICS 20 By understanding how capacitive sensors work and how they can be designed to selftune themselves to compensate for noise, developers can build robust systems that make their appliances more reliable, costeffective, and easier to use.

CONTROLS & SENSORS 24 An introduction to and discussion of reed switches, versatile, low-cost sensing elements frequently used as non-contact proximity sensors.

Paul’s European Perspective

SOCIAL MEDIA Connect with appliance DESIGN on:

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COVER The motor is the key element in designing a washer that’s both energy efficient and quiet. Image: Saint Gobain Performance Plastics. www.applianceDESIGN.com

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EDITORIAL ®

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Is NanoTech an Environmental Concern?

T

he rule in technology is everything always gets smaller. The rule in appliances is the smaller the better. Some devices today are about the size of the original’s smallest parts. Yet as designers experiment with nano-sized materials, environmental regulators are starting to fear what happens if, say, workers, neighbors, or end users accidentally do things like breathe our components. A little more than a year ago EPA issued significant new use rules under the Toxic Substances Control Act for chemical substances dubbed, in the language of government alphabet soup, “MWCNT” and “SWCNT.” To you and me these are multiwalled and single-walled carbon nanotubes. The action required “persons who intend to manufacture, import, or process either of these two chemical substances for a use that is designated as a significant new use by this final rule to notify the EPA at least 90 days before commencing that activity.” It’s nanotubes: everything’s a new use. If you work in displays you’re already well aware of their amazing capabilities. CNTs are electrically conductive, and thus can be used as field emitters in FEDs; think of a microscopic cathode ray tube. Coatings manufacturers are experimenting with CNTs to add various magical abilities, from turning the thing it’s covering invisible to filtering the surrounding air. Although industry experts see great potential for nanotechnology in our industry, there is also great potential for various nano-goods to present a whole new range of dangers to the environment if they’re

publishing staff Darrell Dal Pozzo Group Publisher

simply released into the wild. Speculation that nanomaterials will be regulated has been rampant since at least 2005, when these technologies began hitting the market en force. This was the first rule the agency has finalized regarding actual controls of nano-materials. The agency is currently finalizing a rule to require testing for certain nanoscale materials that are already in commerce. They also have agreements in place through ISO and other organizations to facilitate coordinated controls with other nations. Industry might be one step ahead of them, not just protecting people from nanoscale infections, but treating them. IBM researchers this summer announced they have figured out how to create polymers from nanomaterials that magnetically attract skin cells affected by a nasty, heretofore untreatable skin infection called MRSA. Nanotechnology offers incredibly exciting opportunities for OEMs; in 20 years there may not be a thing with a plug that doesn’t have some sort of nanoparticle in its engineering. Just remember as you play that we’re all likely to be held responsible for cleaning up afterwards. 

(847) 405-4044 [email protected]

Seth Fisher Editor-in-Chief

(248) 244-6248 [email protected]

Daryl Delano Economics Editor

(508) 746-7986 [email protected]

Paul Roggema Kevin Henry New Media Contributors

[email protected]

Lindsay Nagy Production Manager

(248) 244-6438 [email protected]

MaTT Britcher Art Director

(480) 334-0286 [email protected]

circulation Rita Foumia Corporate Strategy Director Christina Roth Audience Development Coordinator

(248) 786-1687 [email protected] (248) 244-6435 [email protected]

Alison Illes Multimedia Specialist

(248) 244-1730 [email protected]

Catherine M. Ronan Corporate Audience Audit Manager

[email protected]

(248) 244-8259

Kevin Collopy List Manager

(800) 223-2194 x684 [email protected]

Michael Costantino

(800) 223-2194 x748 [email protected]

marketing Michele Raska Marketing Coordinator

(248) 786-1694 [email protected]

Chelsie Taylor Events Marketing Assistant

(248) 244-6249 [email protected]

editorial advisory board Bob Brown Vice President, Marketing & Sales, North America, Emerson Industrial Automation John Davis

Business Development Manager, Traulsen

Kevin Henry

Seth M. Fisher, Editor-in-Chief E-mail: [email protected] Twitter: @aplncdsgn

President, Group42

Joseph McGuire

President, Association of Home Appliance Manufacturers (AHAM)

Richard Watson

Founding Partner, Essential

Stephen Yurek, JD President, Air-Conditioning, Heating and Refrigeration Institute (AHRI)

| HVAC | Majors | Water Processing | Housewares | Commercial Appliances | Vending | Medical | Lab | | Test & Measurement | Lawn & Garden | Electronics | Computers | Communications | Business Equipment | APPLIANCE DESIGN (ISSN 1552-5938) is published 12 times annually, monthly, by BNP Media, 2401 W. Big Beaver Rd., Suite 700, Troy, MI 48084-3333. Telephone: (248) 362-3700, Fax: (248) 362-0317. No charge for subscriptions to qualified individuals. Annual rate for subscriptions to nonqualified individuals in the U.S.A.: $178.00 USD. Annual rate for subscriptions to nonqualified individuals in Canada: $216.00 USD (includes GST & postage); all other countries: $228.00 (int’l mail) payable in U.S. funds. Printed in the U.S.A. Copyright 2011, by BNP Media. All rights reserved. The contents of this publication may not be reproduced in whole or in part without the consent of the publisher. The publisher is not responsible for product claims and representations. Periodicals Postage Paid at Troy, MI and at additional mailing offices. POSTMASTER: Send address changes to: APPLIANCE DESIGN, P.O. Box 2148, Skokie, IL 60076. Canada Post: Publications Mail Agreement #40612608. GST account: 131263923. Send returns (Canada) to Pitney Bowes, P.O. Box 25542, London, ON, N6C 6B2. Change of address: Send old address label along with new address to APPLIANCE DESIGN, P.O. Box 2148, Skokie, IL 60076. For single copies or back issues: contact Ann Kalb at (248) 244-6499 or [email protected]

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Intelligent fans for smart savings.

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The engineer’s choice

SHIPMENTS Product

FORECASTS July-11

July-10

%Chg 5 Mo. 2011 5 Mo. 2010

%Chg

MAJOR APPLIANCES (Thousands of Units) Total

4,237.10

4,434.00

-4.40%

37,849.40

38,035.50

-0.50%

Cooking-Total Electric Cooking - Total Electric Ranges Electric Ovens Surface Cooking Units Gas Cooking - Total Gas Ranges Gas Ovens Surface Cooking Units Microwave Ovens

1,137.00 275.1 213.8 38.5 22.8 158.9 136.3 2.1 20.5 703

1,239.10 303.1 235.8 44.9 22.4 196.4 172 2.4 22 739.6

-8.20% -9.20% -9.30% -14.20% 1.70% -19.10% -20.70% -14.50% -6.80% -4.90%

9,272.20 2,406.60 1,896.90 317.8 192 1,420.90 1,231.20 21.3 168.4 5,444.60

9,392.10 2,529.10 1,985.40 342.9 200.8 1,546.90 1,336.90 23.5 186.5 5,316.20

-1.30% -4.80% -4.50% -7.30% -4.40% -8.10% -7.90% -9.20% -9.70% 2.40%

Home Laundry - Total Automatic Washers Dryers - total Electric Gas

800.2 457.3 342.8 273.7 69.2

892.5 506.1 386.3 303.7 82.7

-10.30% -9.60% -11.30% -9.90% -16.30%

7,814.30 4,343.00 3,471.30 2,795.50 675.8

8,318.10 4,570.20 3,747.90 3,022.70 725.2

-6.10% -5.00% -7.40% -7.50% -6.80%

Kitchen Clean Up - Total Disposers Dishwashers - Total Built-In Portable Compactors

791 424.5 363.7 360.5 3.2 2.8

827.2 450.5 373.8 370 3.8 2.9

-4.40% -5.80% -2.70% -2.60% -15.20% -5.00%

6,277.60 3,104.70 3,150.00 3,111.60 38.4 22.9

6,389.70 3,073.70 3,291.00 3,251.80 39.2 25.1

-1.80% 1.00% -4.30% -4.30% -2.00% -8.70%

Food Preservation - Total Refrigerators 6.5 & Over Freezers - Total Chest Upright

908.8 751.7 157.1 86.9 70.2

987.6 819.8 167.8 93.5 74.3

-8.00% -8.30% -6.40% -7.00% -5.60%

6,295.60 5,191.70 1,103.90 653.8 450.1

6,690.20 5,572.20 1,118.00 665.2 452.8

-5.90% -6.80% -1.30% -1.70% -0.60%

Home Comfort - Total Room Air Conditioners Dehumidifiers

600.1 480.4 119.8

487.6 394.5 93.1

23.10% 21.80% 28.60%

8,189.70 7,169.60 1,020.10

7,245.20 5,932.50 1,312.70

13.00% 20.90% -22.30%

Note: Figures (in units) include shipments for the U.S. market whether imported or domestically produced. Export shipments are not included. Source: Association of Home Appliance Manufacturers (AHAM).

HVAC - Shipment figures for unitary air conditioners, heat pumps, furnaces, and water heaters can be found at www.ahrinet.org.

36>*6:;=HYPHISL:WLLK*VU[YVSZ -VY-HUZ)SV^LYZ/\TPKPÄLYZ:[V]LZ/LH[LYZ >OVSL/V\ZL=LU[PSH[VYZ9HUNL/VVKZ3HTWZ DIAL-A-TEMP Plug-In 2.5 Amps-120VAC.

KBWC-Wall Box Mount 2.5, 5.0, 6.0, 8.0, 10.0, 12.0 & 15.0 Amp models, 120 & 240VAC, 50/60Hz.

KBMC-Panel Mount 2.5, 3.0 & 4.0 Amp models, 120 & 240VAC, 50/60Hz.

Designed for Shaded Pole, AC/DC and Permanent Split Capacitor (PSC) Motors. Send for complete literature. If it’s not in our catalog, let KB engineers design a custom control for your application.

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 5> [O:[YLL[‹*VYHS:WYPUNZ-3  ‹-H_! ‹6\[ZPKL-3 ^^^RILSLJ[YVUPJZJVT‹,THPS!PUMV'RILSLJ[YVUPJZJVT

DVD PLAYERS/RECORDERS – Shipments (Thousands of Units) Qtr: 1 2 3 4

2010 5884.4 8376.2 8433.8 10,495.0

2011 5406.5 5872.7 7716.9 11,187.7

2012 5509.2 6324.9 7601.2 11,433.8

For 2011, a 9.1% decline to 30.184 million units For 2012, a 2.3% increase to 30.869 million units Data Source: CEA Forecast Source: Delano Data Insights

ELECTRIC RANGES & OVENS – Shipments (Thousands of Units) Qtr: 1 2 3 4

2010 1078.2 1147.8 1049.8 1172.9

2011 1104.7 1026.8 1088.6 1182.3

2012 1136.7 1099.7 1137.6 1234.3

For 2011, a 1.0% decline to 4.402 million units For 2012, a 4.7% increase to 4.608 million units Data Source: AHAM Forecast Source: Delano Data Insights

RESIDENTIAL GAS WATER HEATERS – Shipments (Thousands of Units) Qtr: 1 2 3 4

2010 1086.9 1033.0 884.0 914.3

2011 1085.5 999.4 893.8 949.0

2012 1119.2 1040.3 933.1 994.6

For 2011, a 0.2% increase to 3.928 million units For 2012, a 4.1% increase to 4.087 million units Data Source: AHRI Forecast Source: Delano Data Insights

UNITARY AIR CONDITIONERS & HEAT PUMPS – Shipments (Thousands of Units) Qtr: 1 2 3 4

2010 1031.3 1917.8 1334.0 884.3

2011 1202.9 2086.8 1460.8 922.3

2012 1195.7 2178.6 1533.8 976.7

For 2011, a 9.8% increase to 5.672 million units For 2012, a 3.7% increase to 5.884 million units Data Source: AHRI Forecast Source: Delano Data Insights

DISPOSERS – Shipments (Thousands of Units) Qtr: 1 2 3 4

2010 1317.3 1305.9 1408.3 1288.8

2011 1333.5 1346.7 1440.7 1328.8

2012 1369.5 1385.8 1486.8 1387.2

For 2011, a 2.4% increase to 5.450 million units For 2012, a 3.3% increase to 5.629 million units Data Source: AHAM Forecast Source: Delano Data Insights

REFRIGERATORS – Shipments (Thousands of Units) Qtr: 1 2 3 4

2010 1953.9 2798.5 2540.0 2076.5

2011 1960.2 2479.8 2611.1 2116.0

2012 2015.1 2670.7 2710.3 2219.6

For 2011, a 2.2% decline to 9.167 million units For 2012, a 4.9% increase to 9.616 million units Data Source: AHAM Forecast Source: Delano Data Insights Note: All forecasts begin in Q3/2011

6 applianceDESIGN October 2011

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NEWS WATCH

ENERGY STAR Moves the Bar n late August the EPA released new eligibility requirements and revised specifications for a number of home appliances, including residential refrigerators, home freezers, dishwashers and room air conditioners to attain or retain ENERGY STAR labeling rights. Incorporating Smart Grid Technology: The agency said it is still evaluating how best to address and encourage Smart Grid functionality in ENERGY STAR specifications such as refrigerators and room air conditioning units. The EPA is currently reviewing various ways that the ENERGY STAR Program could accelerate the adoption of smart grid functionality in the product categories it covers. Two options that are most recently under consideration are an allowance against ENERGY STAR limits and extra recognition for smart grid functionality, for example designating those models as Smart Grid Capable on the ENERGY STAR qualified product lists. Residential Dishwashers will have revised energy and water performance standards as of January 2012. Eligible dishwashers must be 11-percent more energy efficient and 16-percent more water efficient than conventional models. The new dishwashers will be 8 percent more efficient than dishwashers that previously met the ENERGY STAR requirements. According to the agency, 240 models already meet the new levels. Residential Refrigerators & Freezers: The EPA is considering significant changes to re-

O

Image courtesy of Sustainable Chicago

TAX INCENTIVE FOR INSULATING

Several U.S. lawmakers have put forth a bill that would incentivize the use of mechanical insulation to prevent energy loss in equipment such as boilers, HVAC, duct work, and hot/cold water piping. Reps. Don Manzullo, R-Ill., and Tim Ryan, DOhio, and Senators Kirsten Gillibrand, 8 applianceDESIGN October 2011

frigerator specifications that will enable consumers to more easily identify the top performers. On July 11, the agency released a Framework Document for the Version 5.0 specification revision. This Framework presented a reassessment of the current criteria and discussed possible changes under consideration. The agency hopes its changes will allow large models with high absolute energy consumption to still qualify for the ENERGY STAR label. The EPA is also considering proposals around foam-blowing agents and smart grid functionality, after the agency’s research indicated that significant GHG emissions savings may be obtained through the adoption of low Global Warming Potential (GWP) foam-blowing agents. The final specification will be finished in early 2012. Room Air Conditioners: The EPA s proposing a number of different changes as part of the V2.0 specification revision to improve the overall efficiency of room air conditioners. These changes include revising the energy efficiency performance standards, requiring an air filter reminder in all ENERGY STAR qualified models, and an “Energy Saver Mode” that is set as the default operating mode. As noted above, Smart Grid functionality may also be incorporated into room air conditioner units along with the revised specifications to give consumers additional value. These revisions are expected to be completed in late 2011 and will likely take effect in October 2012. 

D-N.Y., and Mike Johanns, R-Neb. in September introduced the Mechanical Insulation Installation Incentive Act of 2011 in both federal legislative houses. The bill would create up to a 30-percent tax deduction to encourage commercial and industrial entities to go beyond minimum mechanical insulation requirements in new construction and retrofit projects and increase their maintenance activities. The incentives essentially add insulation to existing legislation that gives tax breaks for green walls, roofing, windows and lighting.

ELECTRONICS UP DESPITE GRIM CONSUMER CONFIDENCE

Consumer confidence in technology improved in August, according to the latest

CEA Index released in September by the Consumer Electronics Association (CEA). However confidence in the overall economy dropped to its lowest level of the year. Consumer confidence in the overall economy dropped for the fourth straight month. The CEA Index of Consumer Expectations (ICE), which measures consumer sentiment about the broader economy, dropped 0.3 points to 158.8. That’s the lowest level since reaching an all-time low of 157.8 in August of 2010. However consumer expectations for technology spending rose more than four points according to the association’s Index of Consumer Technology Spending (ICTE). The index in August reached 84.4, an increase of 4.6 points. The ICTE, which measures consumer expectations about www.applianceDESIGN.com

NEWS WATCH technology spending, is at its highest level since January and up 4.6 points from this time last year. “Consumers continue to show interest in spending on technology despite an uncertain economic outlook,” said Shawn DuBravac, CEA’s chief economist and director of research. “As consumers pull back spending in other categories, technology continues to benefit.”

ter and explain in part the performance of the market.” The association summarizes market results in both its quarterly tracking reports and trend analysis reports. These reports examine orders and shipments by major product category quarterly and annually with both tables and color graphics. Growth rates and book to bill

ratios are provided for each product category. MCA also provides an economic indicator report, which enables report users to interpret quarterly statistics from the standpoint of macro-economic indicators by individual manufacturing industry, as identified by the North American Industry Classification System (NAICS).

MOTION CONTROL MARKET MAKES 2ND Q COMEBACK

The growth has slowed somewhat, but it has been a good year so far for the motion control market. Orders in second quarter 2011 were up 23.8 percent yearover-year for all product markets monitored by the Motion Control Association. According to the association’s figures, orders were up across the board for the following categories: motion controllers, electronic and AC drives, motors, actuators and mechanical systems, sensors, other ancillary components, and support & services. Compared to first quarter 2011, the market was slightly down in second quarter 2011 and is largely consistent with measures of manufacturing sector performance for the period. Compared to first quarter 2011, second quarter 2011 market results registered an improvement with shipments growing 4.0 percent. Growth was evident across most product categories. “The results of the second quarter strongly suggest that the motion control market recovery has not lost its vigor” noted Paul Kellett, the association’s director of market analysis. “Despite a decline in real gross domestic product, indicators of manufacturing performance have remained strong through the second quarwww.applianceDESIGN.com

applianceDESIGN October 2011 9

NEWS WATCH

MANUFACTURING TECH ORDERS DOUBLING 2010 LEVELS

July U.S. manufacturing technology orders totaled $506.97 million according to the Association for Manufacturing Technology (AMT) and the American Machine Tool Distributors’ Association (AMTDA). This total, as reported by companies participating in the USMTO program, was up 7.3 percent from June and up 92.7 percent when compared with the total of $263.14 million reported for July 2010. With a year-to-date total of $2,975.10 million, 2011 is up 102.9 percent compared with 2010. The United States Manufacturing Technology Orders (USMTO) report, jointly compiled by the two trade associations representing the production and distribution of manufacturing technology, provides regional and national U.S. orders data of domestic and imported machine tools and related equipment. Analysis of manufacturing technology orders provides a reliable leading economic indicator as manufacturing industries invest in capital metalworking equipment to increase capacity and improve productivity. U.S. manufacturing technology orders are also reported on a regional basis for five geographic breakdowns of the United States:

AMT and AMTDA also announced that the two associations are exploring ways to integrate their products and services. The associations have formed a committee made up of staff and board members from both organizations, which will meet and discuss strategic partnerships and a joint approach to important manufacturing issues, as well as consolidated services. The committee will begin its work in the next several weeks and is expected to re-

port back to both organizations by year’s end, according to an AMT press release. “It has always been my goal to find better ways to serve the manufacturing industry,” said AMT president Douglas K. Woods. “This exploration, which we expect will lead to a very close cooperation with AMTDA, is a natural partnership that will help both organizations as they seek to advance manufacturing in the United States.”

COMPANY NEWS HITACHI WINS AWARD FOR LCDS

Hitachi Display Products Group has been voted best LCD supplier and manufacturer by Assodel, the Italian association of electronic component suppliers and distributors. Hitachi was presented with the prestigious award at the annual Assodel gala dinner held in Milan, Italy. HONEYWELL EXPANDING COPPER & TIN REFINING TO MEET SEMICONDUCTOR DEMAND

Honeywell Electronic Materials announced on Sept. 15 it will more than double its refining and casting capacity for high-purity copper and tin at its Spokane, Wash., facility in response to rising demand in the semiconductor industry. Demand for the copper material has been steadily growing as new advanced chip designs continue to require high-purity copper. Additional industry growth has come as memory manufacturers transition from aluminum to copper, according to company representatives. The first phase of the capacity expansion will be complete in the first quarter of 2012; the second phase is expected to be completed by the middle of the year. HOW OLD IS YOUR REGULATOR?

SOURCE: AMT/AMTDA press releases Northeast: $58.38 M 17.9% vs. June 11.3% vs. July 2010 63.6% YTD

Central: $106.98 M 15.2% vs. June 75.7% vs. July 2010 103.6% YTD

Southern: $75.03 M 13.4% vs. June 191.3% vs. July 2010 79.6% YTD

Western: $107.31 M 108.2% vs. June 252.6% vs. July 2010 102.3% YTD

Midwest: $159.26 M 1.0% vs. June 70.2% vs. July 2010 138.5% YTD 10 applianceDESIGN October 2011

To commemorate its 65th anniversary, Maxitrol Co., Southfield, Mich., announced a ‘65 Years & Still Regulating’ contest to find the oldest Maxitrol regulator still in service. The contest runs through Nov. 22, 2011. For contest details go to www.maxitrol.com. MERGERS & ACQUISITIONS:

A. O. Smith, Milwaukee, has completed its acquisition of Lochinvar Corp., and details were finally disclosed. The purchase price of the acquisition was approximately $418 million which was funded from A. O. Smith’s cash and revolving credit facility. The transaction had been on hold pending an FTC waiting period, which the commission terminated in September. Bruker announced on Sept. 12, the signing of an agreement to acquire Center for Tribology Inc. Bruker intends to continue to operate CETR in Silicon Valley and to operate it as a separate Tribology and Indenting business, joining the current AFM (atomic force microscope) and SOM (stylus and optical metrology) businesses in the Bruker Nano Surfaces division. Swedish appliance maker Electrolux AB has completed the acquisition of Olympic Group and intends to delist the Egyptian appliance manufacturer’s shares from the Egyptian stock exchange no later than the first quarter of 2012. www.applianceDESIGN.com

NEWS WATCH LIFE CYCLE COST CALCULATOR FOR FOODSERVICE

A new tool developed by NAFEM and ASTM International defines a standard method for foodservice equipment manufacturers to measure and report the environmental impact of products. ASTM F26.5 Committee on Foodservice Equipment Total Life Cycle Cost and Sustainability NAFEM Technical Liaison Committee Sustainability Calculator for Foodservice Equipment Summary Sheet Manufacturers enter information in light green cells. Outputs and intermediate calculations are in light blue cell. Manufacturer Plant Location Model Number Product Description Date reviewed LifeCyclePhase PointsAwarded PointsPossible PhaseWeight PhaseScore Manufacturing 0 35 25% 0.0 Packaging #DIV/0! 10 25% #DIV/0! Use 0 7 25% 0.0 Disposal 0 15 25% 0.0 Total #DIV/0! Thisscoreisbestusedtocompareequipmentofthesametype.Itisnotanabsolutesustainableratingfortheequipment. EnergyConsumptionTestResults(SeeUsePhaseTab) Results TestStandard IdleEnergyRate UseEnergyRate Other:

WaterConsumptionTestResults(SeeUsePhaseTab) Results TestStandard WaterUseRate

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The Sustainability Calculator is an Excel spreadsheet that provides a standard method for foodservice equipment manufacturers to measure and report the environmental impact of products. It identifies specific environmental factors, awards points to the corresponding factors and calculates a total score. The scores are intended to help clarify environmental impact factors, and provide data for product comparisons that may be used to prepare LEED submittals. The tool is offered as a companion piece to NAFEM’s Life Cycle/Total Cost of Ownership Model. Both tools are available for free at www.nafem.org.

vironmental standards, job creation in the United States, and promotion of American-made products. The nominees are evaluated by three criteria: quality, competiveness and impact. Cliff Chewning, Regional Manager for Customer Service in the Western and Pacific States for Whirlpool Corporation, attended the awards dinner earlier this month. “Whirlpool Corporation has become the largest home appliance company in the world with more than 23,000 U.S. employees. Yet our business was started in the United States in 1911, and we continue to invest in the U.S. to the level of $1 billion over the current five years,” says Chewning. Whirlpool will join the Made in the USA Hall of Fame ranks with other Americanmade companies including Ford Motor Company, Caterpillar, Thorlo Socks and Zippo. Visit madeusafdn.org.

IT BLOGS REPORTING TI SALE RUMORS

Several sources on the Internet are

claiming Texas Instruments’ OMAP business unit is up for sale. The unit produces TI’s ARM chips, which are the processors most commonly used in smart phones. Chipmaker Intel, which doesn’t produce ARM chips, seems the most likely buyer for that reason, but the company denies any interest.

Fuad Abazovi, editor of the IT blog Fudzilla, reported in September that he keeps hearing rumors of TI or its ARM chip market are for sale. Abazovi also noted the company is backing away from Windows 8 development to focus on future Android builds. He doesn’t believe that Intel is the

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MADE IN THE USA

Whirlpool Corp of Benton Harbor, Mich., has been inducted into the Made in the USA Foundation’s Hall of Fame at an awards dinner on July 2, 2011, in Santa Monica, Calif. Whirlpool was the winner of the Large Kitchen Appliances Category. At the foundation’s second annual Hall of Fame celebration, 22 winners were announced from 76 nominees. The foundation was established in 2010 to honor and celebrate companies who contribute to American manufacturing, labor and en-

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www.towermfg.com applianceDESIGN October 2011 11

NEWS WATCH

LG GETS ENERGY STAR GOLD Last month the EPA added a new designation for “Most Efficient” to its ENERGY STAR labeling program, and LG Electronics is immediately snatching up available stickers. The company’s home appliances and consumer electronics have achieved the new designation more than any other manufacturer. The company boasts the first two refrigerators in the industry to meet the rigorous qualifications, eight LED HDTVs and five clothes washers that now carry the label, which recognizes approximately the top 5 percent of green products in their respective categories. “Energy efficiency is a core consideration across the board when LG designs new products, from washing machines and refrigerators to HDTVs and desktop moni-

buyer: “For all we know Nvidia or AMD could be potential customers and the big difference is that AMD might have a hard time raising enough cash to buy the fellow Texan chipmaker. Intel has repeatedly said that it doesn’t need ARM to maintain its lead despite the general opinion that thinks otherwise.” However Aharon Etengoff, managing editor of the blog TG Daily, passed on a rumor from the market research group Forward Concepts that claims Intel is among the interested parties. Etengoff did note Intel’s firm denial that it is considering any ARM architecture.

ILLINOIS GOV VETOES SMART GRID BILL

Illinois Governor Pat Quinn has vetoed a bill that would have allowed the state’s utilities, specifically top utility ComEd, to increase rates in order to pay for implementing smart grid technology across its network. The Energy Infrastructure Modernization Act would have allowed ComEd et al. to raise consumer rates in order to install new digital meters and switches along the grid to better help identify problems. The $2.6 billion project would have increased rates an average of $3.00 per month according to ComEd’s environmental consultant firm Black & Veatch. The firm said the system would essentially pay for itself in consumer savings over the 20-year lifespan of the

12 applianceDESIGN October 2011

tors,” said Wayne Park, president and CEO of LG Electronics USA. “We’re proud that LG is among the first with products to be designated as ENERGY STAR Most Efficient in 2011 and we’re pleased that we have 15 products qualified under this new program. We look forward to more of our products achieving this distinction soon.” The 2011 qualifying refrigerators are the LG French Door Models LFC25776 and LFC21776. Both refrigerators feature a redesigned compressor to maximize energy efficiency. Typically, the compressor is either running at full power or off completely, but the Linear Compressor can vary output depending on need, saving energy by 8 to 17 percent compared to previous models. Other ENERGY STAR products receiving this distinc-

MEETINGS October GPEC: GLOBAL PLASTICS ENVIRONMENTAL CONFERENCE 2011 Oct 17-19 / Atlanta Website: www.sperecycling.org CANADIAN MANUFACTURING TECHNOLOGY SHOW Oct 17-20 / Toronto Website: http://cmts.ca

November MD&M MINNEAPOLIS Nov 2-3 / Minnesapols Hosted by UBM Canon Website: www.mdmminn.com 2011 AHRI ANNUAL MEETING Nov 13-15 / Bonita Springs, Fla. Website: www.ahrinet.org

December BIOMEDEVICE, AN MD&M EVENT Dec 6-7 / San Jose, Calif. Hosted by UBM Canon Website: www.biomedeviceshow.com MD&M ONLINE Dec 13-14 / Online Event Hosted by UBM Canon Website: www.mdmonlineevent.com

January AHR EXPO Jan 23-25 Website: www.ahrexpo.com THERMOSET CONFERENCE & EXPO Jan 24-25 / San Antonio Hosted by Society of Plastics Engineers Website: www.spetopcon.com

ADHESIVE & SEALANT FALL CONFERENCE + EXPO Oct 16-18, 2011/ Indianapolis The Adhesive and Sealant Council (ASC) is a North American trade association comprised of 114 adhesive and sealant manufacturers, raw material and equipment suppliers, distributors and industry consultants, representing more than 75 percent of the U.S. industry with operations around the world. The Adhesive and Sealant Council 2011 Fall EXPO is intended for all suppliers, manufacturers and service providers for the adhesive and sealant industry. The Expo will be held in Junior Ballroom E-F at the JW Marriott Indianapolis Hotel on Monday, Oct. 17, from 4:00 to 7:00 p.m. Website: www.ascouncil.org 

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NEWS WATCH

tion from the company are eight LED HDTVs (Models 42LV3700, 47LV5500, 47LW5700, 55LW5700, 47LW5600, 55LW5600, 47LW6500, and 55LW6500), some of which are 3D TVs and Smart TVs, and five most-efficient washing machines (LG Models WM3550H, WM3150H and WM3360H, plus two OEM models). The models incorporate energy-efficient technology including LED lighting in televisions and the Direct Drive motor and ColdWash option in washers 

LG CEO Wayne Park shows off the grand opening of the company’s newest project: a laundromat opened in early September in New York City’s Harlem district. The energy and water efficiency of the ENERGY STAR-labeled machines is expected to make the facility hyper-competitive due to significantly reduced overhead.

smart meters. Much of that would be up to consumers, who could use the Smart Grid’s 30-minute (as opposed to its current 30-day) readings to better manage their energy use. An overturn is possible, however it

would need to gain votes from nine more senators than supported the bill when it passed—the 59-member chamber voted 31-24 (with four abstentions) to pass the bill in May. It seems that would be an up-

hill battle, as ComEd’s savings estimates are coming under question even by representatives who voted for the initial bill. A vote on an override would take place in October. 

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applianceDESIGN October 2011 13

MOTORS

MESSAGE TO APPLIANCES:

SSSSSH! Reducing noise and vibration in electric motors with tolerance rings

by stuart kelly Stuart Kelly, Market Manager, Appliance and Electric Motors, Saint-Gobain Performance Plastics 14 applianceDESIGN October 2011

O

ne quick glance around a typical household reveals the ubiquity of fractional horsepower motors (FHPs). From refrigerators to vacuum cleaners, washing machines to coffee machines, low output electric motors drive the appliances that we use every day. Indeed, it is only in the automotive sector that FHPs are more commonly found. Despite their varied uses and applications, the FHPs in homes share one common feature: they make noise. The excessive motor vibrations produced by these appliances form an unwanted backdrop to domestic lives, potentially damaging health and creating irritating and disturbing noise pollution. This is no trifling matter. Excessive noise and vibration have a proven negative impact on stress levels and mood, as well as hearing. They place unnecessary strain on the body and mind. For example, the average vacuum cleaner produces volumes equivalent to a tractor at a 15-meter distance, and has to be endured in a confined space, sometimes for prolonged periods – a potentially harmful noise dose. It is with this in mind that manufacturers of FHPs are increasingly focusing on compliance with noise, vibration and harshness (NVH) standards. Alongside cost-competitiveness and efficiency, the reduction of NVH is one of the foremost concerns across all industries that utilize FHPs, presenting a real challenge to engineers.

Hard choices When looking to reduce NVH, an effective starting point is with bearing mount

solutions. The bearing mount has a large impact on NVH in motorized applications that belies its small size. Manufacturers have three primary options when it comes to fixing a bearing in the correct position within FHP motors: press fit, adhesive solutions or tolerance rings. All three options take a different approach toward noise and vibration reduction, with varying degrees of success. Press fit and adhesive solutions, the most common bearing mounts found in FHP motors, are alike in their reliance upon rigidity to fasten the bearing. Press fit, or interference fit as it is often referred to, literally presses the mating components together to create friction, so that one is interfering in the other’s space. Not as robust as soldered or adhesive fittings, compression fittings work very well in industrial devices that face tough environmental conditions, or those which need to be taken apart or modified/ cleaned from time to time. They’re not so great in devices that will experience a lot of turbulence. Adhesive mounting is a considerably less expensive option, using solvents to achieve the same join. Adhesives can vary in quality and stability; today’s high-quality resins can make a hard and seamless joint at the expense of some cost efficiency. Both joins create a stiff mount, and this inflexibility can generate a lot of NVH. This is because the hard mounts cause all vibrations from the motor to be passed www.applianceDESIGN.com

MOTORS

through the assembly. NVH levels, caused by energy in the system or misalignments, are not dampened. Excessive vibration causes energy wastage, unpleasant noise and increased wear, hastening the product’s deterioration.

Tolerance rings Tolerance rings are high-quality steel, radially sprung, engineered fasteners that allow for an optimal join between mating components. The key feature of a tolerance ring is the radial protrusions that run around its circumference, which effectively absorb more of the vibration energy produced by the FHP motor. The principles of tolerance ring design rely on parameters such as assembly force, radial load capacity, spring compression, and slip torque. Tolerance rings are not as rigid, affecting both transmissibility and structure modification to reduce noise and vibration. Not a new technology, improved load generating designs since the early 2000s have made the rings viable in more applications. However the trade-off hasn’t changed: if maximum torque for the design is exceeded, they slip. In a study comparing press fit bearing mounts with tolerance rings using the electric motor from a vacuum cleaner

made possible by tolerance rings combine to create a unique selling point, especially for appliances incorporating AC (alternating current) and brush DC (direct current) motors, which have the biggest challenges with NVH. Particularly in the European Union, products are required to display technical information that specifies performance in energy efficiency and consumption, running costs and noise output - the most efficient products even carry the energy saving recommended logo. Tolerance rings can help manufacturers to achieve this sought-after status.

(turbine removed), tolerance rings consistently produced less total noise (75.3 dB at high end operating range compared to 84.2 dB for press fit mounts).Tolerance rings also performed better in regards to total vibration at all but low end operating ranges (153 dB at high end operating range compared to 160 dB for press fit). Tolerance rings are able to disrupt the path of vibration by acting as spring, thereby reducing transmissibility. To affect modification, engineers are able to alter and tailor the stiffness and dampening characteristics of the tolerance ring bearing mount within a FHP-powered application. However the alterations can only go so far before affecting the rings’ tolerances. Care must be taken in design, especially when tailoring the stiffness and dampening of the ring, to stay well within load conditions, considering worst-case demands during startup, rapid shut-off, or impact loading and overloads. The spring-like qualities of the ring, and the ability to perfect the thickness of material and geometry, allow manufacturers to alter the stiffness of the bearing mount to realise their optimum transmissibility ratio (ratios greater than one lead to amplification while ratios less than one conclude in effective isolation). Through this fine-tuning, manufacturers decrease the ratio of vibration output to input in the system. Housing manufacturing tolerances can be relaxed for reduced manufacturing costs. The noise reduction and energy efficiency

Bearing the brunt Whatever the domestic appliance, choosing the right bearing mount solution can pay rich dividends for those manufacturers who look to the finer details. As consumers pay more attention to the reduction of NVH, manufacturers must seek to confront a hazard the World Health Organization has deemed the principal environmental nuisance in industrial nations.  For more information, visit: www.bearings.saint-gobain.com

About the Author Stuart Kelly is Marketing Manager for Appliances and Electric Motors for the Bearings and Tolerance Rings Business Unit of Saint-Gobain Performance Plastics. He has a degree in HND Production Engineering from the University of West England and a Project Management Diploma from Lancaster University. He can be contacted at +44-1179381700 or [email protected]. Visit www.bearings.saint-gobain.com. Total Vibration

Total Noise

86 82

 Press Fit  Tolerance Ring

80 78 76

76.3

76.1

75.3

74.9

74 72 70

Low End (30k - 31k)

Mid Range (35.5k - 37.5k)

Operating Range (RPM)

www.applianceDESIGN.com

High End (41k - 42k)

Amplitude (dB/1μm/s^2)

Amplitude (dB/20μPa)

84.2

83.7

84

162 160 158 156 154 152 150 148 146 144 142

160

 Press Fit  Tolerance Ring 153

153

150 149 148

Low End (30k - 31k)

Mid Range (35.5k - 37.5k)

High End (41k - 42k)

Operating Range (RPM)

applianceDESIGN

October 2011 15

PROTOTYPING

Testing for Performance

Rigorous performance testing for white goods demonstrates workmanship and usability, specifically as it relates to energy efficiency.

The quality of a quality test depends on whether performance parameters include the ‘how’ as well as the ‘if.’

by steve hartquist Steve Hartquist is the General Manager of the Appliance Energy Efficiency Group for Intertek. He has been involved in various aspects of product energy efficiency testing and regulatory compliance for 24 years, and participated on standards committees of DOE, UL, NFPA and IEC. 16 applianceDESIGN October 2011

“What are you doing daddy?” “I’m working on our washing machine, son.” “What’s wrong with it?” “It’s making a lot of noise.” “Why?” “Because the motor’s not perfectly straight.” “Why isn’t it straight?” “Because it’s old and some of the parts might be out of alignment.” “Why?” “Because it’s been shaking for a long time.” “Why?” ... rustrated yet? You shouldn’t be; these are some of the key questions that the pros ask when defining performance parameters. And like the child who just learned his interrogatives, while technical answers may vary, the performance of any product is revealed by discovering how a product performs: how fast, how much, how many, etc. Although prefaced by seemingly simple questions, the true definition of performance is far more complex and undefined. And there is no one, simple answer.

F

Tech Talk In product testing, performance falls into a few, basic categories. Making its way to the top of the list – from engineers to manufacturers to consumers – is the need to understand how well the product performs its primary function. Once people fully grasp product’s intended use (function), then several other questions arise: How long will it function? How well will it function? Under what conditions will it operate; How easy is it to use? How well is it put together? These questions represent a set of five critical categories that define product performance: Functionality Life Cycle Durability Usability Workmanship

Functionality At face value, functionality is the basis for performance testing. All products must perform at a reasonable level relative to the functions at which the product was designed to perform (e.g. normal use). If consumers www.applianceDESIGN.com

PROTOTYPING

Residential and commercial clothes washers are evaluated in order to meet required specifications at individual test stations. At the same time, calibrated instruments record water consumption, energy consumption, and “cleanability” performance.

purchase your product and it does not work well, that is a direct reflection of functionality. For example, if we examine a residential clothes washer, the appliance usually has a set of controls that are set for various functions to clean wash and wear cottons, whites, delicates, along with a whole host of other combinations. But how well does the product work from the consumer’s point of view? From a cleaning perspective, washing your delicates in the cotton or extra wash cycles will certainly whiten garments, but the material could deteriorate as a result of agitations and durations associated with a heavy wash cycle. However, if the garment is washed on the delicate cycle, the gentle action of this speed will perform as intended, allowing for the delicate material to last longer. But what about temperature? Some garments require a warmer wash cycle as a result of the material used. If this is the case and garments are washing in extra hot water, they may come out clean, but more energy was required to heat the water. A good example of this is defined in the performance test requirements of the Saudi Arabian Standards Organization (SASO) for selling products into the Kingdom of Saudi Arabia. SASO standard 2693 has several performance test criteria that relate to cleanability and severity of action. These requirements are some of the most stringent requirements

to meet. Why? The attributes required to maximize each test are in direct conflict of one another. When developing a new product, a responsible manufacturer will attempt to design products with predetermined use cycles that utilize the best performance design characteristics of the appliance. These “use cycles” also should be in alignment with the perceived needs of the consumer. This meld of technology and consumer experience more exactly defines a functional appliance. For the washing machine example, most appliance designs dictate dedicated, selectable wash cycles which are predetermined and have maximized the performance capabilities of the washer. Again, functionality is a combination of performance of certain attributes. Manufacturers are aware of the energy efficiency requirements as set forth by the US Code of Federal Regulations and knowledgeable of the technical subtleties associated with the test procedures that support these regulations. However the business-savvy manufacturer should not sacrifice a good consumer experience just to meet the minimum performance requirements set by the Environmental Protection Agency. At the end of the day, functionality is the best balance of multiple performance attributes that provide the best consumer experience.

Life Cycle In the consumer electronics world, the life of a product is a game of obsolescence. In the early days of computers, building a tower that would last 10 years was futile, as yearly revisions to software, operating platforms, memory and processor speed requirements would lead to outdated hardware. However, in the case of white goods, consumers usually gauge reliability on how many years they have owned a particular product. Many performance tests are recognized by international and national standards, but some standards need to be customized for the unique attributes or goals of the product. Performance tests serve two key components: Demonstrate a minimum, or Measure an actual value For example, an engineer may have a set a goal for their product to function for five years. To ensure this goal is met, the product will undergo performance testing, which is designed to demonstrate that the product performs for more than five years. This test is done by exposing the product to an equivalent of five years of life, usually through accelerated operational cycles and test exposures. However measuring the product’s actual life requires a different test by which that product is exposed to accelerated conditions and periodically assessed to see at what point in its life cycle it eventually

Usability (the ease of use) is enhanced by providing more options to customize the customers’ experience. Greater control over a stereo’s sound setting increases usability and functionality.

www.applianceDESIGN.com

applianceDESIGN

October 2011 17

PROTOTYPING fails. This second type of performance test takes considerably more time and resources.

Durability Similar to life cycle, durability evaluates the range of conditions a product can handle and continue to function throughout its projected life span. A television can have the best picture quality and the most pleasing attributes, but if the speakers are not durable and turn to static during the first few months of the life of the set, then the product is not durable. Durability testing is usually conducted by setting parameters beyond the expected or designed functional requirements of the product. Testing is then performed to see if the product can function at the end of the duration. This type of performance testing sets levels of durability.

Usability Frequently deemed the highest regarded attribute of a product, usability is all about the customer experience across all functions of a product, both designed and perceived. Consumers have an expectation of how a product should perform. When you buy a gas range stove top for the kitchen, everyone expects the

18 applianceDESIGN October 2011

burners to ignite and the high setting to boil water. Yet if the gas control valve has infinite settings, allowing the owner to adjust the cooking heat by even the slightest variation, now the product is very usable and offers a high level of satisfaction for the consumer. Performance testing for usability encompasses the technical attributes of a product and grades the results on ease-of-use, allowing the highest levels of quality to be achieved. In addition to the technical attributes of a product, usability combines ergonomics, simplicity, automation and consumer appeal into the equation. Many publications make a good living on rating the new products on a schedule basis, and consumers yearn for this comparative information to make buying decisions. Using independent testing to verify the claim prior to making an economic decision is a logical step. After all, would you buy a house without an appraisal?

Workmanship Workmanship is historically equivalent to quality, but it is actually the fit and function of a device. Does the product feel right for the job? Is it robust enough for the task? Is it a quality device that will perform its intended function?

Performance testing will answer these questions. Did you know some manufacturers add weight to a product, for no reason at all but to give the consumer the impression of superior quality? The workmanship and quality of a heavy table-top lamp is frequently valued higher than that of an equally functional, yet lighter, twin. Again, consumer perception wins.

Know By Test Performance testing is the mechanism to gather the data and results that will establish and compare all the performance testing attributes mentioned in this article. The only way to know if these products perform against certain attributes is to physically test them to an established standard or test protocol. Then, and only then, do you have proven data that can be compared in order to establish a good, better, best rating of a product. Delivering quality product performance is dependant on meeting the five key attributes of performance testing. In a sense, the results of these tests are what the client is buying. By meeting the five levels of performance, a company can increase consumer appeal, brand trust and its bottom line.  For more information, visit: www.intertek.com

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ELECTRONICS

THE RIGHT TOUCH Designing reliable touch interfaces for white goods

C

apacitive technology is affected by environmental noise and other factors which can cause systems to not respond to finger touches or to trigger false touches. Unless developers tune sensors, accuracy and reliability can be severely reduced. By understanding how capacitive sensors work and how they can be designed to self-tune themselves to compensate for noise, developers can build robust systems that make their appliances more reliable, cost-effective, and easier to use.

To sense the presence of a finger, a capacitive sensing system must first know the sensor capacitance in the absence of a finger (see Figure 2a), also known as the parasitic capacitance (Cp). When a finger approaches or touches the sensor (see Figure 2b), the sensor capacitance will change, resulting in another capacitance called the finger capacitance (Cf ) in parallel to the Cp. In the presence of a finger, the total sensor capacitance (Cx) is given by Equation 1: Cx = Cp +_ Cf Ground Plane

Sensor

Capacitive Sensing To understand the challenges behind designing a robust user interface, it helps to first take a brief look at the technology behind a capacitive measurement system. Figure 1 shows a cross-sectional view of a capacitive sensor board.

Cp

Figure 2(a): Sensor capacitance in the absence of finger. Finger

CF

by sachin gupta, prakhar goyal and kurian polachan Sachin Gupta, Prakhar Goyal and Kurian Figure 1: Cross sectional view of a capacitive Polachan of Cypress Semiconductor sensing board 20 applianceDESIGN October 2011

Cp

Figure 2(b): Sensor capacitance in the presence of finger

To be able to analyze the sensor capacitance using a microcontroller, the sensor capacitance (Cx) needs to be converted into www.applianceDESIGN.com

ELECTRONICS Clock

Control Logic

IDAC

+ Comp Cx Cmod

Vref

Bit stream

-

Figure 3: Pre-processing circuit for capacitance measurement

Feasibility Study

Schematics Design

PCB Design Review

F/W Development

Mechanical Design

Device Configuration

System Integration

Production Fine Tuning (process variation, vendor change)

Tuning

Design Validation

Mass Production

Figure 4: Touch sense interface design flow

a digital value. Figure 3 shows the block diagram of one of the capacitive sensing preprocessing circuit. (Note: There are several methods for measuring sensor capacitance.) This system uses a switched capacitor block that emulates the sensor capacitance Cx using a resistance Req, a programmable current source (Idac), an external capacitor (Cmod), and a precision analog comparator.

The Idac charges Cmod continuously until the voltage on Cmod crosses Vref and the comparator output is high. The Idac is then disconnected and Cmod discharges through Req until the voltage on Cmod drops below Vref. The comparator output is now low until Cmod charges to Vref again. Cx will be greater in the presence of a finger and the emulated Req will be less according to

Figure 5: Raw sensor data is comprised of finger response and noise. Finger response, also called signal strength, is the difference in raw counts seen by the sensing system when a finger is placed on the sensor. www.applianceDESIGN.com

Equation 2: Req = 1/FsCx …where Fs is the switching frequency of the switched capacitor block. Thus, when a finger is present, Cmod discharges faster and the comparator output stays high for a shorter time. This means that a higher capacitance value corresponds to a shorter high time for the comparator. The resulting bit stream as shown in Figure 1 can be fed to a counter for a fixed amount of time. This counter value or “raw counts” provides an indication of the magnitude of Cx. The fixed amount of time for which the counter counts also determines the number of raw counts and can be referred to as the resolution. When the resolution is increased, the counter counts for a longer period of time and this increases the raw counts. Put another way, resolution is also the highest number of raw counts possible.

Tuning Figure 4 shows the design flow for a capacitive sensor touch interface. However, capacitive sensors must operate in the real world where variations in components, environmental operating conditions, and noise can impact sensor performance and reliability. Tuning is a critical process for ensuring that a sensor functions correctly and consistently. This is achieved by identifying and determining optimum values for a set of sensor parameters to maintain a sufficient signal-to-noise ratio (SNR) and finger threshold. In general, a 5:1 SNR is the minimum requirement for a robust sensor design (see Figure 5). To avoid false triggering caused by changes in capacitive due to atmospheric changes, a finger threshold of between 65-80% of the signal strength is recommended to ensure reliable finger detection. While sensor controller manufacturers provide guidelines to aid engineers in the tuning process, achieve the ideal tuning parameters for the system involves an iterative process. For a sensor controller with a capacitive sensing algorithm implemented similar to the one shown in Figure 3, the tuning procedure will follow the steps shown in Figure 6. Developers can implement tuning parameters either by writing code specific to the operation of the sensors in firmware, through external components, or by configuring the controller. With a firmware approach, developers have flexibility; however, whenever tuning parameters need to be changed, the firmware also needs to be modified and updated. Alternatively, designers can simplify applianceDESIGN

October 2011 21

ELECTRONICS system firmware development by utilizing a fixed-function/non-programmable capacitive sensor controller. Tuning parameters, in this case, must either be implemented using external components on the board or by sending configuration data over a communication interface such as I2C. With this approach, whenever tuning parameters need to be changed, either the user interface board need to be reworked or configuration data needs to be updated. Developers need to be aware that tuning can be time-consuming, especially if the PCB or overlay needs to be changed between iterations.

Production Tuning Capacitive sensor performance is highly dependent on physical property/characteristics of the sensor board and environmental/ operating conditions. For example, sensor performance is affected by sensor capacitance changes due to PCB manufacturing process variations, whenever overlay material or thickness changes, or the PCB vendor changes. The challenges do not stop here. Parasitic capacitance also varies with environmental conditions (noise floor) such as temperature and humidity. Thus, a board tuned in the Alps may not work in the hot and humid climate of Hong Kong, resulting in more time and labor to tune the board again. To minimize yield losses due to process variation or vendor change, tuning needs to take into expected differences based on statistical analysis. There may also be reasons when the board layout needs to be redone, such as changing a button size, moving traces on the PCB to incorporate minor changes in the schematic, resizing the PCB to address different EMC/ EMI issues, and so on. All of these modifications require that sensors be tuned again. Moreover, the tuning process needs a communication protocol and a host-side application to observe and analyze the raw sensor data. Extra I/O will be needed since tuning must be done after the final board has been made, creating potential issues for systems with pin constraints. It is clear that tuning is not an easy job to do, requiring significant expertise and experience with the chips involved and an understanding of capacitive sensing effects at very low signal levels. When coupled the time-tomarket constraints of the appliance market, tuning can impose significant delays and increases to system cost. To cost-effectively handling design constraints and market needs, tuning is most efficiently implemented to be handled by the

22 applianceDESIGN October 2011

Start Set the default value to all tuning parameters Get raw count using some communication interface

Increase Resolution or decrease scan speed

Obtain the signal count by touching the sensor and calculate SNR

SNR >=5 ? Choose the sensor with higehest raw count Calculate the parasitic capacitance (Cp) of that sensor Based upon Cp, calculate the clock to make sure that sensor charges and discharges completely

Decrease Resolution or increase scan speed of sensor whose SNR is highest

Set the IDAC value to get the raw count in the range of 65% to 80% of maximum count

Total Scan Time