EEWeb Pulse - Issue 72

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EEWeb PULSE INTERVIEW

EEWebIssue 72

November 13, 2012

Electrical Engineering Community eeweb.com

Auto-calibrationCapacitiveSensors

TECHNICAL ARTICLE

Fiber Optics forWind Turbines

TECHNICAL ARTICLE

Chairman & CEOZigBee

BobHeile

http://bit.ly/kDYHm7

EEWeb PULSE TABLE OF CONTENTS


Bob Heile ZIGBEE ALLIANCE

Interview with Bob Heile - Chairman and CEO

How NXP is taking a new approach to capacitive sensors that lets the sensor adjust itself continuously to its environment.

RTZ - Return to Zero Comic

Featured Products

BY EMMANUEL T. NANA WITH NXP SEMICONDUCTORS

4

11

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20

Capacitive Sensors with Auto-Callibration

Fiber Optic Products for Wind Turbine

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Applications

For Human Touch Interfaces

4


EEWeb | Electrical Engineering Community

BobZigBeeHeile



BobZigBeeHeile

ZigBee Alliance offers green and global wire-less standards that contribute to the ever-ex-panding internet of things. We spoke with the CEO and Chairman, Bob Heile, about imple-menting a standard, the growing global eco-system using the standards and the future of the wireless sensor industry.

6



How did you get into engineering?I have been active in the data communications field since when modems were considered state-of-the-art. I ran the modem business for Motorola Codex throughout the 1980s and grew that business up from what was basically a hardware thing up into the modern age of signal processing and all of the things we take for granted in our PCs today. I got into wireless at the same time because wireless local area networking was a very interesting new area. It wasn’t until the late 80s, when there were unlicensed ISM (Industrial, Scientific, Medical) bands, that they were even practical to consider. I launched that with a group and we started the company Wireless Area Local Networking.

The initial findings wound up being one of the founding members of 802.11 in 1990. At the end of the decade, I started doing the

got started with 802.15.4, which is the radio technology that was really adapted for sensor networks. I formed a joint venture with an industry group developing market requirements for sensor networks that was out there, looking at similar process from the marketing side. That joint venture is what morphed into the ZigBee alliance in 2002.

Tell us about the ZigBee Alliance. What are some of the goals and objectives you have?

The Alliance was formed ten years ago with a very simple mission. We had a core group of companies that were very interested and surveyed the landscape and what existed in terms of wireless standards. Those standards were ones that were near and dear to my heart because I was involved with their creation, mainly 802.11 and Bluetooth, but neither of those technologies were suitable for

global standards for wireless sensor networks. It was viewed then, and emerging to be the truth now, that it was going to be a very important paradigm moving forward. That was what we set out to do initially, but there was one more piece to that, which is a little different than the usual standards development organization. Usually you write the standard and you’re done with it, but we felt that it was very necessary to have a good, unbiased, 3rd party mechanism to do certification and authentication so that manufacturers could verify that their products could interoperate.

The whole point of a standard, especially in the case of wireless sensor networks, is achieving interoperability. We actually set up a certification program, validated at groups at certified test houses, either independent organization, so the company anonymity is preserved when you’re out there

same thing again, but low-power radio technology because of the impending opportunity, which is how 802.15 got launched. Back then, Bluetooth was just getting started, so I started a joint venture with Bluetooth and 802.15.1 was the IEEE standard version of BT. The more important stuff was when we

what today we’d call the “internet of things,” which could be networks of thousands of devices. 802.11 is a great WLAN. Bluetooth is a great peer-to-peer wireless headset, but that’s not what the mainstream problem is for sensor networks. The mission was to establish an organization that could create

certifying products. That’s been very successful. Today, we’re over 425 companies worldwide. Over half of the organization’s members are outside North America, so when I say it’s a global organization, I mean it. With all of the efforts and activities, we’re starting to see some real market take-up. We

“Like I said, [the standard] has successfully solved a lot of the unique problems of sensor

networking, which is the ability to scale to large sizes, the ability to be self-organized and solving

security issues and battery power efficiency.”


EEWeb PULSE INTERVIEW are declared as having cross the chasm in 2010 and we’ve have seen certified products growing since that time at a rate of 4.3% over the last 11 months, so it’s now over 540 certified products. We have the go-to standard for smart-metering and home area networking. Like I said, it has successfully solved a lot of the unique problems of sensor networking, which is the ability to scale to large sizes, the ability to be self-organized and solving security issues and battery power efficiency.

We are a Standard Development Organization (SDO). We’re organized as a 501c6, just like IEEE.

need to attend to. The alliance is there to create standards and my role is to create an organization that allows companies to do that in an effective way and to manage those standards and to evolve them and improve them over time.

I also try to educate the community and marketplace whenever I can about what they need and what’s happening. If you have a good set of standards and people like them, then the rest follows—I get more and more involved. We aren’t necessarily going after members, we are going after the mission of creating global standards for wireless sensor

We legally exist to help companies get together and develop open, public standards. We have no other mission and no other product aside from global standards.

What is your position at the ZigBee Alliance?

My position is Chairman of the ZigBee Alliance and Chief Executive Officer. Basically, my mission is to make sure things are going smoothly and people are tending to what they

networks and we’ve been very successful at that and we have a very large community of interest out there as a result—420 member companies are now participating in the standards process. It’s a very lively global ecosystem.

In what ways do work with companies in the Alliance?

A function the Alliance performs on behalf of its members is talking about the capabilities and the

mission with other companies. We also engage in trade shows and technology events and set things up where we sometimes have a booth or a speaking position. These events really become an opportunity for the companies to gain visibility. We talk to users as well, because they understand what is there and what is capable so that they can go back and ask their suppliers for the appropriate product because it will solve the specific problem that they face. It’s not sales, but things

“Over half of the organization’s members are outside North

America, so when I say it’s a global

organization, I mean it.”

8



that drive understanding of the products. We bring various OEMs together to share their development experiences with people who are just starting out. It allows people to get a good understanding and also gets people acquainted with design tricks and stuff to help people along. The attitude in the market is, in part, understanding what other people have done and what decisions have been made so that they can make intelligent decisions.

What do you see as the biggest challenges for large, mass adoption?

It varies. Even though a wireless sensor network is very generic in architecture and character, we’re not out there building a grand internet of things from the bottom up. We think about home automation and about commercial building automation. What this

means is that we not only design a standard networking capability, but an application that allows for interoperability. We’re seeing, for instance, home automation and smart energy have been growing the fastest because, in the case of energy management, we know we have shortages of electricity, we know we need to do residential demand response. Building the smart-grid is strategically important to a lot of nations. The challenges for smart energy is making people comfortable in the early market phase, that this technology is not just a flash in the pan, but it will be around for years to come, because that’s the lifetime of these designs.

Do you have tools that help hardware developers integrating into the standards?

Absolutely. We have seven of the world’s top ten companies

in the Alliance and we have a number of fabless semiconductor companies—so it’s a very rich ecosystem. On the ZigBee website, there’s a “Products” page and all of the silicon providers all have training and development kits to help with designs and to see the network performance. There’s a lot of good stuff you can pick from and a lot of good companies that can help you do it.

What is the future of the ZigBee Alliance? What are some of your goals?

It’s pretty much what it has been in the past, except now we are in the mode of where the standards now are in very wide deployment around the world, particularly in the smart energy arena, which is not a static arena. The way the wireless sensor networks has been unfolding, eventually there will be enough



market vertical that they will knit together in sort of a seamless internet of things, but that’s not the case now. It’s been easier for the marketplace to work at home automation, remote controls, retail and energy, so now we have ten of those verticals and there’s more coming. It’s a very active area as companies look at how they can benefit from growing a particular segment, by having a common application as well as a common network. That job is not done, and we’ll continue at that for quite some time. Meanwhile, as we

“The challenges for smart energy is making people comfortable in the early market phase, that this technology is not just a flash in the pan, but it will be around for years

to come, because that’s the lifetime of these designs.”

gain more and more experience, there’s additional features and additional capabilities that we want, and we’ve just added one called ZigBee Light Link, which is really aimed at the do-it-yourself or general purpose consumer marketplace. It has very integrated communications inside and you’ll be able to create very simple in-home lighting networks with no computer required. Over the next several years, we’ll see expansion of these systems and they’ll gradually merge into a seamless and completely

ubiquitous internet of things, but it’s going to take a lot of work and additional standards, gateways and bridges before we get the systems worked out.

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EEWeb PULSE TECH ARTICLE

12 EEWeb | Electrical Engineering Community

Emmanuel T. NanaNXP Semiconductors

CapacitiveSensorswith Auto-Calibrationfor Human TouchInterfaces



Emmanuel T. NanaNXP Semiconductors

CapacitiveSensorswith Auto-Calibrationfor Human TouchInterfaces

One popular way to use capacitive sensors is to replace mechanical switches. There are fewer parts involved, which saves cost and increases reliability, and the novelty of proximity/touch interfaces can make the end product more desirable. For example, the proximity feature can be used in cell phones and anti-tampering devices, to detect when the equipment is close to an object or not. Touch-free operation is also useful in environments that use hazardous or explosive materials, since no contact is required, and in medical applications, because the user can still control the system while

wearing surgical gloves, and thus maintain a sanitary environment. Proximity sensing

also benefits hermetically sealed applications, since the sensor works

with dielectric material sandwiched between two electrodes.

One drawback of proximity sensors, however, is the trouble they have compensating for changes in the environment over time. Changes in humidity, for example, dirt collecting on the

sensor area, or a change in the moving object can impact sensitivity

and reduce performance.

NXP Semiconductors is taking a new approach that lets the sensor adjust

itself continuously to the environment. NXP’s PCF8883, PCA8885, PCF8885, and PCA8886 capacitive sensors use a patented auto-calibration technology to detect changes in capacitance. The devices digitally filter out very slow and very quick changes in capacitance at the input. As a result, the performance of the NXP devices is less affected by conditions that can impair or prevent correct functions in other devices. With auto-calibration, such things as dirt, humidity, freezing temperatures, or damage to the electrode do not affect the device function.



Theory of Operation

The device has two resistor-capacitor (RC) timing circuits. The first is connected to the IN pin, which connects to the external sensing plate, and the sec-ond is used as a reference. The discharge time (tdch) of the input RC timing circuit is co pared to the discharge time (tdch(ref)) of the reference RC timing circuit. Both RC timing circuits are periodi-cally charged from VDD(INTREGD) via identical synchronized switches and then discharged via a resistor to ground (VSS).

The charge-discharge cycle is governed by the sampling rate (fs). If the voltage of one of the RC timing circuits falls below the internal reference voltage Vref, the respective comparator output will become LOW. The logic following the comparators determines which comparator switches first. If the upper (reference) comparator switches first, then a pulse is given on CUP to count up. If the lower (in-put) comparator switches first, then a pulse is giv-en on CDN to count down. The pulses control the charge on the external capacitor, CCPC, on CPC pin. Every time a pulse is given on CUP, CCPC capacitor is charged from VDD(INTREGD) for a fixed time, causing the vol age on CCPC to rise. Likewise, when a pulse occurs on CDN, CCPC ca-pacitor is connected to a current sink to ground for a fixed time, causing the voltage on CCPC to fall.

If the capacitance on the IN pin increases, the tdch discharge time increases and it will take longer for the voltage on the corresponding comparator to drop below Vref. Only once this happens does the comparator output become LOW, with the re-sult that a pulse on CDN slightly discharges the ex-ternal CCPC capacitor. Thus most pulses will now be given by CUP. Without further action, CCPC capacitor would then fully charge. However, the auto-calibration mechanism, which is based on a voltagecontrolled sink current (Isink) connected to the IN pin, attempts to equalize the tdch discharge time with the tdch(ref) internal reference discharge time.

The current source is controlled by the voltage on CCPC, which causes the capacitance on the IN pin to be discharged more quickly in the case that

the voltage on CCPC is rising, thereby compensat-ing for the increase in capacitance on the IN pin. This arrangement constitutes a closed-loop control system that constantly attempts to equalize tdch with tdch(ref). This allows compensating for slow changes in capacitance on the IN pin. Fast chang-es, due to an approaching hand, for example, will not be compensated. In the equilibrium state, the discharge times are equal and the pulses alternate between CUP and CDN.

From this also follows that an increase in capaci-tor value CCPC results in a smaller voltage change per pulse CUP or CDN. As a result, the compensa-tion due to internal Isink current is slower, and the sensitivity of the sensor will increase. Similarly, a decrease in CCPC capacitor will result in a lower sensitivity. Following the sensor logic depicted in Figure 1, the counter counts the pulses of CUP or CDN respectively. The device only switches its output when the capacitance changes more than 63 times consecutively in one direction. Very slow changes are neutralized. and extremely quick changes don’t register because the device never reaches the required number of changes for a switch. The counter is reset every time the pulse sequence changes from CUP to CDN or vice versa.

Sample Application

The sensing plate is connected to a coaxial cable, which is in turn connected to the IN pin. (The sens-

Figure 1: Functional diagram of capacitive sensor PCF8883



ing plate can also be connected directly to the IN pin.) An internal low-pass filter is used to reduce RF interference. For added RF immunity, an addi-tional low-pass filter, consisting of a resistor RF and a capacitor CF, can be added to the input. Resistor RC reduces the discharge time such that the inter-nal timing requirements are fulfilled by assisting the internal current sink. RC is only required for larger sensor capacitances.

Sensitivity and response time are the two primary items to take into account when fine-tuning switch performance. In this next section, we look at these two factors and make recommendations for opti-mizing the design.

Sensitivity

If the sensitivity is increased, the possibility of in-correct switching due to interference from electri-cal fields also increases. This has a strong influ-ence on the switching characteristics and may be compensated by reducing the sensor area. On the other hand, increasing the sensitivity lets the sen-sor react at a longer distance, and improves the range through materials with different permittivity.

Approach speed and dynamics

The sensor compensates for changes in static or slowly changing capacitance. As mentioned above, the autocalibration feature means that the sensor

requires more than 63 consecutive increases (or decreases) in capacitance over a fixed period to cause a switch at the output. The first switch occurs when the sensor can no longer compensate the change in capacitance. A triggering object, moving at a constant speed, will cause a greater change in capacitance as it approaches the sensing plate. As the approach speed increases, the required dis-tance from the switch increases as well. If the dis-tance between the sensor plate and the triggering object is larger than the sensor plate area, then a certain amount of fine-tuning may be required.

Area of the sensor plate

The size and form of the sensor plate can be varied to obtain optimal switching behavior or to conform to the size constraints of the application. Oval and round areas are usually best, since they present the fewest edge effects, but there is considerable flex-ibility in sensor design.

In keyboards, the keys typically have a relatively small surface area. In this case, the sensor area needs to be roughly comparable to the size of a fin-gertip, and the switch must be fine-tuned such that neighboring switches don’t react in error.

The capacitance is proportional to the cross-sec-tional area of the sensing plate. In most cases, simply increasing the sensing area will lead to an

Figure 2: Typical connections for a general application



improvement in sensitivity. When the sensing area is limited by the application, the value of CCPC ca-pacitor has to be increased to increase the sensitiv-ity.

Using a bigger triggering object can also increasesensitivity. This may prove useful in certain applica-tions, such as when switching through a thick layer of material where the material itself influences the sensitivity.

Thickness and nature of the dielectric

The dielectric encompasses everything between the sensing area and the triggering object area. The thickness and nature of each dielectric influ-ences the strength and flux of the electrical field passing through. The electrical field will be refract-ed, diffracted, reflected, or diminished depending on the exact materials used, and on the thickness of the construction.

Materials having higher relative permittivity sup-port higher sensitivity because the electrical field strength is proportional to the relative permittivity, and inverse proportional to the thickness. An ex-ample is a sensor area mounted behind 10 mm of glass, a 0.3 mm air gap, and 2 mm of plastic. The air gap is an issue, since its relative permittivity is low compared to the plastic and glass. Therefore, air gaps should be minimized and the thickness of the material should be reduced to a minimum. By placing conductive foam between the sensor plate and the glass, the air gap can be avoided com-pletely.

Plate (electrode) orientation

The more field lines that the triggering object cuts, the larger the generated capacitance change will be. For instance, an approaching palm area trig-gers a switch faster than the side of the hand. For this reason, it’s important to position the sensing plate in a way that makes it easy for the user’s natu-ral touch or proximity motion to trigger a change.

Response Time

The value of the CCLIN capacitance connected on the CLIN pin determines the internal sam-

pling frequency and therefore the reaction time of the switch. Figure 5 shows that smaller values of CCLIN correspond to faster reaction times.

The sensor reacts more quickly when the frequency is increased, since the necessary number of com-parisons is reached in less time. This also means that the sensor self-calibrates to new environments more quickly, with the result that a slow-moving hand will no longer cause the sensor to switch. That is, the sensor calibrates itself to the new envi-ronment (with the hand present) more quickly than it detects the changes caused by the approaching hand. Another consequence of increasing the sam-pling frequency is that the sensor reacts to quick changes at a distance with higher sensitivity. This effect can be enhanced by increasing CCPC or the sensing area.

To get the proper dimension of CCLIN, it’s impor-tant to know the normal approach speed of the trig-gering object. For example, a machine may move faster than a human does, and a single finger can often move more quickly than an entire hand.

It’s important to keep in mind that increasing the response time (and thereby reducing the switching frequency) reduces power consumption. As shown in figure 6, the higher sampling frequencies associ-ated with shorter reaction times lead to increased current consumption, and that uses more energy. Depending on the application, the designer has to find the best trade-off between speed and power consumption.

Other Considerations for Power Con-sumption

The capacitive sensors from NXP offer very low power consumption. The single-channel PCF8883 consumes less than 5 μA, even under worst-case conditions.

Supply voltage and temperature also have an im-pact on power consumption. NXP’s devices sup-port a wide range of supply voltages (from 2.8 to 9 V), and offer low current consumption at lower supply voltages (see Figure 7).



Figure 8 shows that more power is required to drivethe devices at low temperatures.

Conclusion

By enabling human interfaces that can be con-trolled by proximity or touch, capacitive sensors have the ability to transform the way we interact with electronic systems. Until now, a limiting fac-tor has been reliability, since environmental factors such as humidity, dirt, freezing temperatures, and changes in the moving object can have a negative impact on sensitivity and responsiveness.

NXP Semiconductors, with its PCF8883, PCA8885, PCF8885, and PCA8886 capacitive sensors, takesadvantage of a patented auto-calibration feature that improves reliability. Designing with auto-calibration requires a certain amount of fine-tuning, since the switch has to be optimized for typical application requirements, but once the initial configuration is set, the sensor offers enhanced performance and longevity. As a result, these auto-calibrating devic-es are expanding the reach of capacitive sensors, and bringing a new level of user friendliness to a wider range of applications.

Figure 5: Switching time (tsw) with respect to capacitor on pin CLIN (CCLIN)

Figure 6: IDD with respect to sampling frequency (fs)

Figure 7: IDD with respect to VDD (PCF8883)

Figure 8: IDD with respect to temperature (PCF8883)

Low Voltage ORing FET ControllerISL6146The ISL6146 represents a family of ORing MOSFET controllers capable of ORing voltages from 1V to 18V. Together with suitably sized N-channel power MOSFETs, the ISL6146 increases power distribution efficiency when replacing a power ORing diode in high current applications. It provides gate drive voltage for the MOSFET(s) with a fully integrated charge pump.

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TABLE 1. KEY DIFFERENCES BETWEEN PARTS IN FAMILY

PART NUMBER KEY DIFFERENCES

ISL6146A Separate BIAS and VIN with Active High Enable

ISL6146B Separate BIAS and VIN with Active Low Enable

ISL6146C VIN with OVP/UVLO Inputs

ISL6146D ISL6146A wo Conduction Monitor & Reporting

ISL6146E ISL6146B wo Conduction Monitor & Reporting

FIGURE 1. TYPICAL APPLICATION FIGURE 2. ISL6146 GATE HIGH CURRENT PULL-DOWN

VIN GATE VOUT

GND

ADJ

+

-

+

VOUT

+

-

+ COMMONPOWERBUS

Q1

ISL6146BFLT

BIAS

VOLTAGE

DC/DCVOLTAGE

DC/DC

EN

(3V - 20V)

(3V - 20V)

Q2

COMMONPOWERBUS

VIN GATE VOUT

GND

ADJISL6146B

FLT

BIAS

EN

GATE FAST OFF, ~200ns FALL TIME~70ns FROM 20V TO 12.6V ACROSS 57nFGATE OUTPUT SINKING ~ 6A

October 5, 2012FN7667.3

Intersil (and design) is a registered trademark of Intersil Americas Inc. Copyright Intersil Americas Inc. 2011, 2012All Rights Reserved. All other trademarks mentioned are the property of their respective owners.

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for Wind Turbine Applications

Fiber Optic Products



outstanding performance in high insulation voltage and high immunity to EMI, these products can be installed to operate in close proximity to power-carrying conduits which emit disruptive electrical interference. As the demand for renewable energy grows globally, wind turbine designs are becoming larger and larger. Avago Technologies’ industrial fi ber products off er a wide range of data-rate and link lengths for many applications in this power generation market.

Key applications for industrial fi ber optic components in a wind turbine system include:

• Power electronic gate driver for rectifi ers and inverters

• Control and communication boards

• Turbine control units

• Condition monitoring systems

• Wind farm networking

Alek IndraAvago Technologies

for Wind Turbine Applications

Fiber Optic Products

Global warming and climate changes from CO2 emissions of traditional energy sources, such as those powered by fossil fuels, have created huge markets for alternative power generation. Wind turbine energy has become a popular alternative to meet the fast growing energy demand. Unlike fossil fuels, which are a limited and diminishing resource, wind energy is limitless and readily available.

Conversion of wind energy into utility grade AC power requires power electronics, such as rectifiers and inverters. In a high power generation system, galvanic insulation becomes very important to ensure the quality and reliability of the power generation. Fiber optic components offer protection by providing insulation from high-voltage glitches and unwanted signals in power electronic devices.

Avago Technologies offers highly reliable industrial fiber optic components for data-acquisition/control and isolation in the power generation market. Featuring



Wind turbine power is used to convert kinetic energy into electrical energy through the use of a generator. As wind conditions vary, the electrical energy created from the generator needs to be converted for usability. A rectifier, inverter, transformer and fi lter are needed within the wind turbine for utility-grade AC power to be transmitted over long distances (Figure 1).

A transformer is usually installed at the bottom of the tower to provide voltage conversion from the low voltage generated by the wind turbine, to medium/high voltage for transmission.

Rectifier and Inverter

The rectifi er and inverter are key components in the wind turbine system. The rectifi er converts noisy AC power to DC power, while the inverter converts DC power to clean and reliable AC power. The switching of these devices is usually controlled by a DSP-embedded controller via a fiber optic link, to provide effi cient and reliable switching control with high galvanic isolation capability.

There are numerous rectifier and inverter control switches available:

• Insulated Gate Bipolar Transistor (IGBT)

• Gate Turn Off Thyristor (GTO)

• Integrated Gate Commutated Thyristor (IGCT)

• Symmetrical Gate Commutated Thyristor (SGCT)

• Emitter Turn Off Thyristor (ETO)

Fiber optic components are commonly used to control a high voltage and current switching device, with reliable control and feedback signals (Figures 2 and 3).

Condition Monitoring System

Most modern wind turbines have intelligent features to monitor and control the system to accommodate varying wind conditions. For example, atmospheric sensors detect wind speed and direction. Other sensors monitor

Industrial Fiber Optic Products for Wind Turbine and Wind Farm Applications

White Paper

Introduction

Global warming and climate changes from CO2 emissions of traditional energy sources, such as those powered by fossil fuels, have created huge markets for alternative power generation. Wind turbine energy has become a popular alternative to meet the fast growing energy demand. Unlike fossil fuels, which are a limited and di-minishing resource, wind energy is limitless and readily available.

Conversion of wind energy into utility grade AC power requires power electronics, such as rectifi ers and inverters. In a high power generation system, galvanic insulation becomes very important to ensure the quality and reliability of the power generation. Fiber optic com-ponents off er protection by providing insulation from high-voltage glitches and unwanted signals in power electronic devices.

Avago Technologies off ers highly reliable industrial fi ber optic components for data-acquisition/control and

isolation in the power generation market. Featuring out-standing performance in high insulation voltage and high immunity to EMI, these products can be installed to operate in close proximity to power-carrying conduits which emit disruptive electrical interference. As the demand for renewable energy grows globally, wind turbine designs are becoming larger and larger. Avago Technologies’ industrial fi ber products off er a wide range of data-rate and link lengths for many applications in this power generation market.







Wind Turbine Power Generation

Figure 1. Wind Turbine Power Generation Block Diagram

Wind Turbine Blade UtilityGrade AC

Power

Fiber Optic Fiber Optic

Fiber Optic

Generator3 Phase Line

Filter andTransformer

InverterDC–AC

Recti-erAC–DC

DCLink

Control Board andCommunication

Turbine ControlUnit (TCU)

By Alek Indra

2

Wind turbine power is used to convert kinetic energy into electrical energy through the use of a generator. As wind conditions vary, the electrical energy created from the generator needs to be converted for usability. A rectifi er, inverter, transformer and fi lter are needed within the wind turbine for utility-grade AC power to be trans-mitted over long distances (Figure 1).


Rectifi er and Inverter

The rectifi er and inverter are key components in the wind turbine system. The rectifi er converts noisy AC power to DC power, while the inverter converts DC power to clean

and reliable AC power. The switching of these devices is usually controlled by a DSP-embedded controller via a fi ber optic link, to provide effi cient and reliable switching control with high galvanic isolation capability.

There are numerous rectifi er and inverter control switches available:







Figure 2. IGBT Gate Driver Block Diagram

Figure 3. ETO Two-Level Voltage Source Converter Phase Leg Block Diagram

Gate Driver

Driver

Control Board

Versatile LinkHFBR-0500Z series


POF

C

GIGBT

Driver Logicand

Protection Functions

E

Rg

GateDriver

Over CurrentProtection

PWMCommand

CurrentControl

Controller

GateDriver

Versatile LinkHFBR-0500Z series Versatile Link

HFBR-0500Z series

POF

V+

V–

Dp

Dn

ETOp

ETOn

2

Wind turbine power is used to convert kinetic energy into electrical energy through the use of a generator. As wind conditions vary, the electrical energy created from the generator needs to be converted for usability. A rectifi er, inverter, transformer and fi lter are needed within the wind turbine for utility-grade AC power to be trans-mitted over long distances (Figure 1).


Rectifi er and Inverter

The rectifi er and inverter are key components in the wind turbine system. The rectifi er converts noisy AC power to DC power, while the inverter converts DC power to clean

and reliable AC power. The switching of these devices is usually controlled by a DSP-embedded controller via a fi ber optic link, to provide effi cient and reliable switching control with high galvanic isolation capability.

There are numerous rectifi er and inverter control switches available:







Figure 2. IGBT Gate Driver Block Diagram

Figure 3. ETO Two-Level Voltage Source Converter Phase Leg Block Diagram

Gate Driver

Driver

Control Board



POF

C

GIGBT

Driver Logicand

Protection Functions

E

Rg

GateDriver

Over CurrentProtection

PWMCommand

CurrentControl

Controller

GateDriver

Versatile LinkHFBR-0500Z series Versatile Link

HFBR-0500Z series

POF

V+

V–

Dp

Dn

ETOp

ETOn



Industrial Fiber Optic Products for Wind Turbine and Wind Farm Applications

White Paper

Introduction

Global warming and climate changes from CO2 emissions of traditional energy sources, such as those powered by fossil fuels, have created huge markets for alternative power generation. Wind turbine energy has become a popular alternative to meet the fast growing energy demand. Unlike fossil fuels, which are a limited and di-minishing resource, wind energy is limitless and readily available.

Conversion of wind energy into utility grade AC power requires power electronics, such as rectifi ers and inverters. In a high power generation system, galvanic insulation becomes very important to ensure the quality and reliability of the power generation. Fiber optic com-ponents off er protection by providing insulation from high-voltage glitches and unwanted signals in power electronic devices.

Avago Technologies off ers highly reliable industrial fi ber optic components for data-acquisition/control and

isolation in the power generation market. Featuring out-standing performance in high insulation voltage and high immunity to EMI, these products can be installed to operate in close proximity to power-carrying conduits which emit disruptive electrical interference. As the demand for renewable energy grows globally, wind turbine designs are becoming larger and larger. Avago Technologies’ industrial fi ber products off er a wide range of data-rate and link lengths for many applications in this power generation market.







Wind Turbine Power Generation

Figure 1. Wind Turbine Power Generation Block Diagram

Wind Turbine Blade UtilityGrade AC

Power

Fiber Optic Fiber Optic

Fiber Optic

Generator3 Phase Line

Filter andTransformer

InverterDC–AC

Recti-erAC–DC

DCLink

Control Board andCommunication

Turbine ControlUnit (TCU)

By Alek Indra

the condition and strength of the turbine’s parts to avoid run-to-failure.

Wind turbines need to withstand extreme weather conditions, such as storms and lightning. In these conditions, it is important to ensure that the turbine’s monitoring system is designed to provide high voltage and current isolation. Fiber optics becomes a preferred choice of medium as it off ers much higher voltage and current isolation properties compared to optocouplers and other similar components.

In the nacelle of the wind turbine (Figure 4), short link distances

using fi ber optics can utilize POF (plastic optical fiber) and Avago Technologies’ HFBR-0500Z products. Designers can select from connectors with snap-in, latching, and screw-in designs. Avago Technologies’ versatile link sub-family allows fi eld connector capabilities for POF and the associated connectors, allowing for field repairs, maintenance, and installation.

Besides good isolation properties, these products provide excellent signal integrity as they are immune to electro-magnetic interference (EMI). They are an excellent solution for monitoring system communications over long distances with reliable data transmission in high voltage/current applications.

For greater ESD and EMI protection, Avago Technologies’ HFBR-0506AMZ series off ers a metalized packaging that provides excellent shielding. The SMA-styled connector also works well in areas with vibration and mechanical shocks.

3

Table 1. Common Avago Technologies’ Fiber Optic Components Part Numbers

Part Numbers Description Data RateDistance*

POF (1mm) HCS® (200μm)HFBR-1521ETZ 650 nm, Transmitter DC – 5 MBd 20 m

HFBR-2521ETZ 650 nm, Receiver

HFBR-1522ETZ 650 nm, Transmitter DC – 1 MBd 43 m


HFBR-1528Z 650 nm, Transmitter DC – 10 MBd 40 m 300 m

HFBR-2528Z 650 nm, Receiver

AFBR-1624Z, AFBR-1629Z 650 nm, Transmitter DC – 50 MBd 50 m

AFBR-2624Z, AFBR-2529Z 650 nm, Receiver* Optical link distance varies with operating data rate. Lower data rate allows longer optical link distance.HCS is a registered trademark of OFS


Most modern wind turbines have intelligent features to monitor and control the system to accommodate varying wind conditions. For example, atmospheric sensors detect wind speed and direction. Other sensors monitor the condition and strength of the turbine’s parts to avoid run-to-failure.

Wind turbines need to withstand extreme weather condi-tions, such as storms and lightning. In these conditions, it is important to ensure that the turbine’s monitoring system is designed to provide high voltage and current isolation. Fiber optics becomes a preferred choice of medium as it off ers much higher voltage and current isolation properties compared to optocouplers and other similar components.

In the nacelle of the wind turbine (Figure 4), short link distances using fi ber optics can utilize POF (plastic optical fi ber) and Avago Technologies’ HFBR-0500Z

products. Designers can select from connectors with snap-in, latching, and screw-in designs. Avago Technolo-gies’ versatile link sub-family allows fi eld connector capa-bilities for POF and the associated connectors, allowing for fi eld repairs, maintenance, and installation.

Besides good isolation properties, these products provide excellent signal integrity as they are immune to electro-magnetic interference (EMI). They are an excellent solution for monitoring system communica-tions over long distances with reliable data transmission in high voltage/current applications.


Figure 4. Elements within a Wind Turbine Nacelle Requiring Fiber CommunicationsWind Turbine Development: Location of Manufacturing Activity, S. George and S. Matt, “Renewable Energy Policy Project”, September 2004

3

Table 1. Common Avago Technologies’ Fiber Optic Components Part Numbers

Part Numbers Description Data RateDistance*

POF (1mm) HCS® (200μm)HFBR-1521ETZ 650 nm, Transmitter DC – 5 MBd 20 m


HFBR-1522ETZ 650 nm, Transmitter DC – 1 MBd 43 m


HFBR-1528Z 650 nm, Transmitter DC – 10 MBd 40 m 300 m

HFBR-2528Z 650 nm, Receiver

AFBR-1624Z, AFBR-1629Z 650 nm, Transmitter DC – 50 MBd 50 m

AFBR-2624Z, AFBR-2529Z 650 nm, Receiver* Optical link distance varies with operating data rate. Lower data rate allows longer optical link distance.HCS is a registered trademark of OFS


Most modern wind turbines have intelligent features to monitor and control the system to accommodate varying wind conditions. For example, atmospheric sensors detect wind speed and direction. Other sensors monitor the condition and strength of the turbine’s parts to avoid run-to-failure.

Wind turbines need to withstand extreme weather condi-tions, such as storms and lightning. In these conditions, it is important to ensure that the turbine’s monitoring system is designed to provide high voltage and current isolation. Fiber optics becomes a preferred choice of medium as it off ers much higher voltage and current isolation properties compared to optocouplers and other similar components.

In the nacelle of the wind turbine (Figure 4), short link distances using fi ber optics can utilize POF (plastic optical fi ber) and Avago Technologies’ HFBR-0500Z

products. Designers can select from connectors with snap-in, latching, and screw-in designs. Avago Technolo-gies’ versatile link sub-family allows fi eld connector capa-bilities for POF and the associated connectors, allowing for fi eld repairs, maintenance, and installation.

Besides good isolation properties, these products provide excellent signal integrity as they are immune to electro-magnetic interference (EMI). They are an excellent solution for monitoring system communica-tions over long distances with reliable data transmission in high voltage/current applications.


Figure 4. Elements within a Wind Turbine Nacelle Requiring Fiber CommunicationsWind Turbine Development: Location of Manufacturing Activity, S. George and S. Matt, “Renewable Energy Policy Project”, September 2004



Wind Turbine and Wind Farm Networking

Data collected from the condition monitoring systems, with the use of short-link POF fi ber links in individual wind turbines, are typically multiplexed into HCS (hard-clad silica) or multi-mode fi ber cables. The longer link distances of HCS and multi-mode fi ber may be needed if wind turbine towers are greater than 100meters in height. Fiber cables are both robust, off er greater resis-tance to harsh environmental elements, and are light-weight. All of these are requirements for vertical cabling in wind turbine towers.

Industry standard connectors like the ST/ST-thread and SMA are all available from Avago Technologies. The HF-BR-0400Z series operates over both HCS and multi-mode fi ber, which off er greater bandwidth and link distance compared to the POF solution. These parts are commonly used in wind turbine towers and over long distance wind farm networks.

Avago Technologies has developed a series of fi ber optic transmitters, receivers, and transceivers for wind turbine monitoring systems and networking applications.

off ers parts from 650nm, 820nm, or 1300nm, which have data rates up to 160MBd to meet customer needs over various link distances.

Figure 5. Wind Farming Confi guration

Server ComputerSystem

SwitchCONTROL CENTRE

Controller

DataAcquisition

System

NetworkSwitch

Table 2. Common Avago Technologies Fiber Optic Components Part Numbers

Part Numbers Description Data Rate

Distance*

POF (1mm) HCS® (200μm) 62.5um/125umAFBR-1624Z, AFBR-1629Z 650 nm, Transmitter DC – 50 MBd 50 m -

AFBR-2624Z, AFBR-2529Z 650 nm, Receiver -

AFBR-5978Z 650 nm, Transceiver 125 MBd 50 m 100 m -

AFBR-5972Z 650 nm, Transceiver 125 MBd 50 m

HFBR-14X4Z 820 nm, Transmitter 160 MBd - - 500 m

HFBR-24X6Z 820 nm, Receiver

HFBR-1312TZ 1300 nm, Transmitter 160 MBd - - 2 km

HFBR-2316TZ 1300 nm, Receiver

HFBR-57E5APZ 1300 nm, Transceiver 125/155 MBd 2 km* Optical link distance varies with operating data rate. Lower data rate allows longer optical link distance.HCS is a registered trademark of OFS

For product information and a complete list of distributors, please go to our web site: www.avagotech.com

Avago, Avago Technologies, and the A logo are trademarks of Avago Technologies, Limited in the United States and other countries.Data subject to change. Copyright © 2007-2012 Avago Technologies Limited. All rights reserved. AV02-0732EN - July 26, 2012




Data collected from the condition monitoring systems, with the use of short-link POF fi ber links in individual wind turbines, are typically multiplexed into HCS (hardclad silica) or multi-mode fi ber cables. The longer link distances of HCS and multi-mode fi ber may be needed if wind turbine towers are greater than 100meters in height. Fiber cables are both robust, off er greater resistance to harsh environmental elements, and are lightweight. All of these are requirements for vertical cabling in wind turbine towers.

Industry standard connectors like the ST/ST-thread and SMA are all available from Avago Technologies. The HFBR-0400Z series operates over both HCS and multi-mode fiber, which off er greater bandwidth and link distance compared to the POF solution. These parts are commonly used in wind turbine towers and over long distance wind farm networks.

Avago Technologies has developed a series of fi ber optic transmitters, receivers, and transceivers for wind turbine monitoring systems and networking applications and offers parts from 650nm, 820nm, or 1300nm, which have data rates up to 160MBd to meet customer needs over various link distances.









Controller

DataAcquisition

System

NetworkSwitch



Distance*












For more information and a complete list of distributors, please go to Avago’s website:

www.avagotech.com









Controller

DataAcquisition

System

NetworkSwitch



Distance*












www.avagotech.com

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Thanks to a patented auto-calibration technology, the capacitive sensors can detect changes in capacitance and continually adjust to the environment. Things such as dirt, humidity, freezing temperatures, or damage to the electrode do not affect the device function. The rise of touch sensors in modern electronics has become a worldwide phenomenon, and with NXP’s low power capacitive sensors it’s never been easier to create the future.

Learn more at: touch.interfacechips.com

World’s lowest power capacitivesensors with auto-calibration

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EEWeb Pulse - Issue 72

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