I promised in my last blog to give you the run down on the SPS show. Well, first there’s Nurnberg. Nurnberg is an old city that’s about an hour train ride north of Munich, which I think still counts as Southern Germany (Bavaria), though I could be wrong.

Nurnberg seems to be an odd place for this show. Northern Germany is the heart of German Industrial might. While Nurnberg is centrally located, it doesn’t have the manufacturers you would find in Stuttgart or Hannover. I’m glad the show is there though, as it doesn’t have the distractions of Munich and is much prettier than the northern German cities.

Here are my top takeaways from the show:

IT’S HUGE

The first thing about this show is that it is huge. There are twelve halls. Three I think are dedicated to anything and everything having to do with Motion Control. From Motors to systems, if you can’t find it at SPS, no one makes it. But the really weird thing is the shape of the halls. They’re not rectangles. Not even pentagons or octagons. One is a triangle with rounded corners. Another is sort of a rectangle with a ball on the end, and so on. Not only that, but it’s really hard to walk through them because the aisles go in all sorts of odd directions.

THE FOOD

If you like to eat, you’ll love this show. Vendors here aren’t into the logo’d up pen or luggage tag type of giveaways. Here, you eat (and drink). At the high end, the Siemens, Phoenix Contact, and Wago’s of the world have essentially complete restaurants in their booths. You can get sausage dinners or Wiener schnitzel with beer, wine, and cocktails. At the next level, you can get sandwiches, pretzels and some German bakery. At the lowest level, everyone has cookies and candy. Some companies were even handing out Schnapps and other liqueurs.

THE LANGUAGE BARRIER

Lots of attendees didn’t speak English. Maybe I’m an Anglophile but I pretty much believed that if you are an Engineer anywhere in the world you have a pretty good command of English. Well, that’s not the case. Lot’s of people moving through our booth were not English speakers. They recognized DeviceNet, EtherNet/IP, Modbus TCP but that’s about it.

WIRELESS

I didn’t see anywhere near the amount of wireless I expected. Maybe because I am working on wireless everyday now I am more sensitive to it, but it just wasn’t there. I’m not talking about the 803.11 Wireless Ethernet routers and gateways. Everybody has those - it’s old hat. But I barely saw any cellular, Zigbee or other sensor networking, even in the “wireless area” which wasn’t more than two small booths.

STUDENTS

Germans are big into Engineering education. There were many teachers taking students on tours, so a large portion of attendees were much younger than you would see in the US.

WOMEN

This is short. There weren’t any. Almost no women working in booths. A few companies used them to accessorize their booths but they were mostly the typical German style women (I won’t comment further). 98% of the wait staff doing food duty were women, but that was about it. Engineering is a very male dominated profession in the US, but in Germany it appears to be even more so. However, there was one very popular, nearly naked woman for some company in Hall 6 - I’ll post a picture if I get some requests.

EUROPE SALES BARRIERS

Distributor after distributor explained to me how hard it is to sell in Europe across country lines and even within a country. In Switzerland for example if you’re from Lucerne (German part) you have a really tough time selling in Geneva (French part). In France, you have to be French. In Belgium, Holland and other places it’s the same way. If you’re not like me, I don’t buy. I was totally unaware of this problem before the show.

It was a great show, our booth was a success and I am glad I got to experience it - sinus infection and all.

We’ve been talking in previous articles about features and characteristics of 802.15.4, the level 2 ISO radio interface defined by the IEEE. This article will focus on more of the low level radio characteristics of the standard:

But before that let’s review what 802.15.4 is and isn’t:

·       It is a short range communication standard for ISM (Instrument, Scientific and Medical) applications. Depending on the specific frequencies used it can go as far as several kilometers but usually 15.4 nodes are found within 10 to 100 meters of each other.

·       It isn’t a Bluetooth replacement – 15.4 has no capability to transfer voice communications.

·       It is a low cost standard designed to add radio communications to small, stand alone, often battery powered sensors and actuators.

·       It isn’t a LAN replacement – At the low data rates it offers (115Kb) you’d be very unhappy connecting your laptop to a server over 15.4. But if you wanted a temperature update from a thermometer every 5 minutes, that’s a perfect low data rate 15.4 applications.

·       It is a low power, low duty cycle technology. Nodes using 15.4 sleep most of the day and when they transmit, it’s in short bursts with tiny amounts of energy.

·       It isn’t a high speed network. Best case data transfer is only 250Kb/sec.

·       It is an intermittent connection network where nodes are expected to come and go and constant connections are unusual.

·       MOST OF ALL IT ISN’T a NETWORK OR APPLICATIONS STANDARD. There is nothing in the 802.15.4 standard concerning routing data or anything that defines the contents of messages. Higher level protocols like Wireless Hart or Zigbee do that. 802.15.4 is just a mechanism to move some amorphous data from one node to another through the air.

There are certain key attributes of 802.15.4 radios:

PHYSICAL CHARACTERISTICS – The 802.15.4 standard defines three frequency spectrums, 868MHz (Europe), 915Mhz (North America, Australia) and 2.4GHz (Most of the world). Within these frequencies, one or more channels are defined. A wireless communication channel is a transmission path from one node to another. The more communication paths or channels that are available, the more simultaneous conversations that can occur. 802.15.4 Defines a single channel for 868MHz, 10 channels for 915MHz and 16 channels for 2.4Ghz operation.

BANDWIDTH – 15.4 is a low bandwidth network solution. At 2.4Ghz you can get 250Kb/s. It’s even less for 868Mhz (20Kb/s) and 915MHz (40Kb/s).

POWER – 15.4 devices transmit a very low power signal compared to 802.11 (WiFi) and 802.3 (Bluetooth). Typical power for a 15.4 transmission is 1mw. That’s about 30 times less than your cell phone.

LOW DUTY CYCLE OPERATION – 802.15.4 is a network designed for device applications that require infrequent data transmission. A lot of 15.4 applications require so little power that batteries can be used in devices with an expected lifetime of ten years or more.

SPREAD SPECTRUM – All 15.4 radios incorporate spread spectrum modulation techniques spread the data signal across the frequency spectrum. This improves the signal to noise ratio and improves it’s immunity to interference.

ENERGY DETECTION & LINK QUALITY – All 15.4 radios are required to incorporate Energy detection & Link Quality assessment.

OPEN CHANNEL ASSESSMENT – When multiple channels are available a 15.4 radio will use the Energy Detection & Link Quality circuitry to assess the relative chance of communicating on a particular channel and select the optimum channel.

There is, of course, a lot more that could be described about 15.4 radios. There are things like how it uses orthogonal signaling to trade off bandwidth to recover sensitivity and the settling times on power up but that gets really geeky and it beyond the needs of anyone who’s not designing CMOS radio circuits.

What’s pretty interesting though is that data receiving is a lot more power hungry operation than transmitting. It’s much more power efficient to blindly transmit than to blindly receive for the same amount of time. It turns out that there are a lot more filters active on receive than on transmit so receiving consumes vastly more power. This becomes very important if you’re planning on using a 15.4 radio in a battery powered application.

In the next segment of this series we’ll discuss the how 15.4 defines access to the channels provided by the radio.

Personal Area Networks (PAN) – A Simple Primer

The previous two articles in this series described the IEEE specifications for radios commonly used in Industrial and Building Automation (IA and BA) applications. We compared these radios to Ethernet. Instead of wire, the transceivers and media access software used in radios sends data over the air instead of through wire.

From that broad overview on radio technology discussed in the previous articles we are going to focus more closely on 802.15.4, also called Personal Area Networking but often confused with Mesh, Zigbee, Wireless Hart and other technologies. For the most part, those technologies are software built on the basic infrastructure known as 802.15.4.

So why is 802.15.4 the base technology for all these wireless systems when there is a plethora of technologies that could be used? The reason is that 802.15.4 has the right features for many applications we find in building, home and building automation.

It’s obvious that no technology can meet the requirements of every application. Remote data collection in the Sahara or the Arctic requires satellite. High data throughput or long range data applications are usually cellular. But for the majority of IA and BA applications 802.15.4 provides the best combination of features that makes it nearly ideal for these applications. These same features also make it close to ideal for Medical, Gaming, Home Automation and other applications. Here are some of the reasons why:

COST – Target applications for 15.4 devices are thermostats, level sensors, medical sensors and a host of low data rate devices. Most if not all of these devices are single point. Making a cost effective radio solution that is viable for single point analog or discrete signals was a major focus for the 15.4 technology definition team.

POWER – 802.15.4 are pretty low power systems making them excellent for low data rate applications. A 15.4 radio might use just 3 Milliwatts of power where your cell phone uses a whopping 3 Watts. And unlink your cell phone 15.4 radios aren’t on all the time. They’re on only when necessary making them almost ideal for battery powered applications that transmit data sporadically. An 802.15.4 node can spend most of its day snoozing. That’s perfect for your conference thermostat but not very good for I/O on your high speed conveyor line.

SHORT RANGE – 802.15.4 is designated as a PAN, a Personal Area Network. That means devices within 10-75 meters which is similar to your home WiFi (10-100m) but considerably more than your Bluetooth headset (10m).

LOW DATA RATES – 15.4 is designed for those applications that don’t send a lot of data therefore it doesn’t need a lot of speed. In fact, the highest data rate for 15.4 is for is only 250Kb (2.4Ghz operation). And the data rates are less for other frequencies; 20Kb for 868Mhz and 40Kb for 915Mhz. These data rates, though small, are entirely satisfactory for the majority of sensor devices in building and industrial automation.

In our next article we’ll explore the 802.15.4 Physical interface. How does data get on the air and what are the important electrical characteristics of an 802.15.4 radio?

John Rinaldi is the Technical Sales Manager for Real Time Automation in Brookfield, Wisconsin. RTA specializes in industrial and building automation software, hardware, systems and specialty controllers. He can be reached on 262-439-4999 or through the RTA website, http://www.rtaautomation.com/forms/contactus.html.

The IEEE (Institute of Electrical and Electronic Engineers) defines the standards for radio just as it does for Ethernet and many other things. In Ethernet the standard is known as 802.3. The 802 is the set of standards that talks about local area networks and something called Metropolitan Area Networks. If you want to get specific for a second, the 802 standard covers variable packet size networks and subset 3 (802.3) within the standard defines the Ethernet we all know and love.

If we talk about Ethernet for a moment, the 802.3 standard defines the physical network and how devices access that physical network. The physical network is the electrical properties of the bits on the wire. It defines the voltage levels, the duration of a bit, the speeds that are used; anything and everything about the electrical characteristics of the signals on the wire. The media access part defines the how and when of messaging on the network. It defines the lowest level message structure, how collisions are handled, how messages are validated and, most importantly, when messages can be inserted onto the network.

One of the most important parts of the media access is collision processing. In Ethernet, collisions are really bad news. If two nodes try to transmit at the same time, there’s a collision, the message is lost and, more importantly, that message slot goes unused. Both nodes try again at some random later time. As more and more nodes try to use the network, the number of collisions increases, there’s more unused message slots and the throughput drops. This protocol for detecting and managing collisions is known as CSMA (Carrier Sense Multiple Access).

The IEEE has specified similar kinds of characteristics for wireless networks. These characteristics define the physical and media access for each of the different kinds of wireless networking. There are a bunch of these standards. Here are a few that are important to industrial and building automation:

802.11 – Wireless LAN, the standards for Local Area Networks, the kinds of networks we use in Homes, Airports and Offices. This is our everyday, long range, high speed, high throughput, power intensive wireless.

802.15 – Wireless PAN, the standards for Personal Area Networks. The original standard covered small numbers of nearby devices typically within 10 meters of each other. These radios are now advanced to the point where the practical range for some of them is up to a mile and advances in routing technology are now making networks of tens of thousands of devices possible. Though the range and count have expanded, low power is still a key factor for devices on PAN networks.

There are two important PAN substandards:

802.15.1 – Bluetooth (True PAN since it is in your immediate area), the radios in our cell phones linking our cell phones to our ears.

802.15.4 – Mesh Networking. This standard covers radios designated for ISM (Instrument, Scientific and Medical) uses. Applications for 15.4 radios are growing at an exponential rate in all these areas.

802.16 – Wireless Broadband MAN, standards for Metropolitan Area Networks.

802.20 – Wireless Mobile Networking

IEEE 802.11 is the standard that is used for most of the PC wireless connections we work with every day. All our home wireless, office wireless and hotspots we use all follow the 802.11 standard. 802.11 devices are great but don’t really fit a lot of wireless automation needs. 802.11 offers an incredibly high data rate but that’s not necessary for a lot of automation applications. For example, most temperature sensors don’t need to report very often and when they do, there is only a tiny bit of data to report.

802.11 devices also require quite a bit of power and that’s something that we don’t have in a many remote devices. In fact we want these remote devices battery powered so we don’t have to run power lines. 802.11 devices are really designed to support applications where the devices are constantly connected not devices that sleep 99% of the time and wake occasionally to transmit a tiny bit of data.

For all these reasons and more, automation applications use 802.15.4 as the basis for most industrial and building wireless. In our next article we’ll take a close look at 802.15.4.

Wireless Radios – A Simple Primer

Wireless technology is on the march. Wireless is showing up in everything from street lights to power cables. This is the first in an ongoing series explaining the various components and key technologies that comprise Wireless PAN Technology.

If you want to really know what all those wireless buzz words like Zigbee, WPAN, Wireless Hart and what they really mean, be prepared to spend some time on it. It is a very complicated area, and one that few people really understand.

It’s an important area right now. The whole wireless area for people working in Industrial, Scientific or Medical (ISM) fields is exploding with new applications. New standards, smaller, inexpensive devices and long lasting batteries are making product opportunities and solutions available that were unheard of just a few years ago.

But if you really want to know wireless then the radio is the place to start. It’s the core of all these solutions and determines how suitable a specific device is for a particular end user application.

If your device uses a 900 MHz radio for example, it’s going to blast through a lot of walls and other structures to make a connection. Great, you say? Well, not so fast. 900 MHz is pretty much a standard around here, in North and South America. If you want to use that same application in Europe, well now you’re out of luck. They have a different frequency spectrum and they prohibit that 900 MHz radio. They use 868 MHz and 2.4 Ghz. And if you replace your 900 MHz radio with a 2.4 Ghz radio, well then you’ve limited both your maximum range and how well you can penetrate any structures that are in the way. And that may be important in some of your applications.

There are lots of factors that go into industrial radio development and they all influence what applications you can do, where you can deploy it and how well it is going to work in those applications. Before we get to those we should make a comparison. In wired systems, we have…ready for this…wire. There are different kinds of wire, there’s twisted pair for RS232 and RS485 and there’s CAT5 (and CAT6) for Ethernet. There are other specific types of wire for Profibus, CAN and ControlNet. Each one of those has a specific MAC (Media Access Controller) and PHY (Electrical Interface).

In RS232, the UART (1 byte to 11 bit frame) can be thought of as the MAC part of the communications while the RS232 driver (15v bit levels) is the Physical Interface (PHY). In CAN and Ethernet, there is a similar MAC usually embedded in a microprocessor and a PHY that does the conversion of microprocessor data bit to data bit on the wire. For RS232 the data bit on the wire is 15 volts. For RS485, it’s 5 volts and for CAN it can be up to 33 Volts. There’s a specific PHY for every specific media.

Now in wireless, we have a single transmission medium, air, but different radios, or transceivers (transmitter/receiver), with different MACs and PHYs for sending messages through that medium. There are transceivers for cellular, satellite, Bluetooth, mesh and many other types of radios. Each type can be described by a key set of features:

Licensing – Does the radio use a licensed or unlicensed radio band? All radios are licensed. You really can’t transmit much of anything with out an authorization from the federal government of whatever country you’re in. Currently, most of what we transmit is in the unlicensed band. That means that the person transmitting doesn’t have to hold a license but the manufacturer has one. Opposite of unlicensed transmission is licensed band transmission. That’s for those applications where every transmitter site must be licensed. Think of your over the air TV and radio. Those stations have a license for every transmitter and are strictly regulated as to power output and frequency.

Frequency – this is how fast a transmitter sends a complete cycle, usually measured in Hertz. In the US, you’ll typically find 2.4 Giga Hertz and 915 Mega Hertz. Europe also uses 2.4 but also had an 868 MHz standard. And there’s new standards emerging for China, India, Russia and other places.

Power Output – This is the amount of power output generated by the radio. The power output is directly related to the range of the radio and somewhat related to how well the radio can penetrate obstacles. A typical industrial radio might put out 30 milliwatts while your cell phone emits a whopping 3 watts.

Spread Spectrum – To avoid narrow band interference (interference from point sources on a single channel) many industrial radios incorporate spread spectrum. This means that the narrow band radio signal is spread out over a much wider bandwidth. There are two types of spread spectrum systems, direct and frequency hopping. In direct sequence, the radio signal is multiplied by a predetermined pseudo random bit sequence. In random spread spectrum, the bit sequence is used to move the signal around in a random fashion.

Data Rate – This is the number of bits that can be transferred over the air by the radio. It is usually expressed in kbps (thousand bits per second). For the kinds of radios we’re discussing, WPAN (Wireless Personal Area Network) Radios, it’s a fairly slow medium. Some radios are only 9600 baud, less than what a lot of RS232 interfaces use. Others use 250 Kbps, still slow compared to the 10 or 100 Mbps of wired Ethernet systems.

In our next article we’ll take a look at all the standards that govern industrial wireless.

John Rinaldi is the Technical Sales Manager for Real Time Automation in Brookfield, Wisconsin. RTA specializes in industrial and building automation software, hardware, systems and specialty controllers. He can be reached on 262-439-4999 or through the RTA website, http://www.rtaautomation.com/forms/contactus.html.

The IEEE (Institute of Electrical and Electronic Engineers) defines the standards for radio just as it does for Ethernet and many other things. In Ethernet the standard is known as 802.3. The 802 is the set of standards that talks about local area networks and something called Metropolitan Area Networks. In general the 802 standard is for variable packet size networks and subset 3 (802.3) is Ethernet.

In 802.3 the IEEE defines the physical network and the media access for Ethernet. The physical network is the electrical properties of the bits on the wire. It defines the voltage levels, the duration of a bit, the speeds that are used; anything and everything that defines the electrical characteristics of the signals on the wire. The media access part defines how and when messages can be inserted into the network. It defines the basic message structure, how collisions are handled, how messages are validated and, most importantly, when messages can be inserted onto the network.

One of the most important parts of the media access is collision processing. In Ethernet, collisions are really bad news. If two nodes try to transmit at the same time, there’s a collision, the message is lost and, more importantly, that message slot goes unused. Both nodes try again at some random later time. As more and more nodes try to use the network, the number of collisions increases, there’s more unused message slots and the throughput drops.

The IEEE has specified similar kinds of characteristics for wireless networks. These characteristics define the physical and media access for each of the different kinds of wireless networking. There are a bunch of these standards. Here are a few that are important to industrial and building automation:

802.11 – Wireless LAN, the standards for Local Area Networks, the kinds of networks we use in Homes, Airports and Offices .

802.15 – Wireless PAN, the standards for Personal Area Networks. The idea behind PAN  is that they are smaller networks but the technology has changed such that Mesh neworks can now have hundreds and thousands of nodes . There are two important PAN substandards:

802.15.1 – Bluetooth (True PAN since it is in your immediate area)

802.15.4 – Mesh Networking

802.16 – Wireless Broadband MAN, standards for Metropolitan Area Networks.

802.20 – Wireless Mobile Networking

802.11 is the standard that is used for most of the PC wireless connections we work with every day. All our home wireless, office wireless and hotspots we use are all 802.11. 802.11 devices are great but don’t really fit a lot of wireless automation needs. 802.11 has an incredibly high data rate but that’s sure not needed in most automation applications. For example, most devices that report temperatures don’t need to report them very often and when they do, there is only a tiny bit of data to report.

802.11 devices also require quite a bit of power and that’s something that we don’t have in a remote device powered by a small battery. 802.11 devices are designed to support applications where the devices are constantly connected instead of devices that wake up, transmit some data and go dormant again.

For all these reasons and more, automation applications use 802.15.4 as the basis for most industrial and building wireless. We’ll look at 15.4 in more detail in the next installment of this series.

If you want to know more about how all these wireless systems really work be prepared to spend some time on it. It is a very complicated area and one that a lot of people know just a little about.

But if you really want to know industrial wireless then the radio is the place to start. It’s the guts of everything and for a large part determines how well your end user application is going to work. And where it is going to work.

If the device you make has a 900 Mhz radio for example, it’s going to blast through a lot of the walls in your customers building. Great, you say? Well, not so fast. 900 is pretty much a standard around here, in North and South America. If you want to sell your device in Europe, well now you’re out of luck. They have a different frequency spectrum and they prohibit 900 Mhz. They use 868 and 2.4 Ghz. And if you replace your 900 with a 2.4 Ghz radio, well then you can’t go very far through the walls of a building.

There are lots of factors that go into industrial radio development and they all influence what applications you can do, where you can deploy it and how well it is going to work in those applications.

Before we get to those we should make a comparison. In wired systems, we have…ready for this…wire. There are different kinds of wire, there’s twisted pair for RS232 and RS485 and there’s CAT5 (and CAT6) for Ethernet. There are other specific types of wire for Profibus, CAN and ControlNet. Each one of those has a specific MAC (Media Access Controller) and PHY (Electrical Interface).

In RS232, the UART is the MAC part of the physical communications while the RS232 driver is the Physical Interface (PHY). In CAN and Ethernet, there is a MAC usually embedded in a microprocessor and a PHY that does the conversion of microprocessor data bit to data bit on the wire. For RS232 the data bit on the wire is 15 volts. For RS485, it’s 5 volts and for CAN it can be up to 33 Volts.

Now in wireless, we have a single transmission medium, air, but different radios, or transceivers (transmitter/receiver), with different MACs and PHYs for sending messages through that medium. There are transceivers for cellular, satellite, mesh, Bluetooth and many other types of radios. Each type is usually described by a set of key features:

Licensing – Does the radio use a licensed or unlicensed radio band? All radios are licensed. You really can’t transmit much of anything with out an authorization from the federal government of whatever country you’re in. Now most of what we transmit is in the unlicensed band. That means that the person transmitting doesn’t have to hold a license but the manufacturer has one. Opposite of unlicensed transmission is licensed band transmission. That’s for those applications where every transmitter site must be licensed. Think of your radio and over the air TV. Those stations have a license for every transmitter and are strictly regulated as to power output and frequency.

Frequency – this is how fast a transmitter sends a complete cycle usually measured in Hertz. In the US, you’ll typically find 2.4 Giga Hertz and 900 Mega Hertz. Europe also uses 2.4 but also had an 868 MHz standard.

Power Output – This is the amount of power output generated by the radio. The power output is directly related to the range of the radio and somewhat related to how well the radio can penetrate obstacles. A typical industrial radio might put out 30 milliwatts while your cell phone emits a whopping 3 watts.

Spread Spectrum – To avoid narrow band interference (interference from point sources on a single channel) many industrial radios incorporate spread spectrum. This means that they continuously change frequencies. If there is interference on one frequency, it’s not a problem because the next message is sent on another frequency. There are two types of spread spectrum systems, direct and random. In direct, the radios use a table of frequencies to sequence through. In random spread spectrum, a random algorithm is used to determine the next frequency.

Data Rate – This is the number of bits that can be transferred over the air by the radio. It is usually expressed in kbps (thousand bits per second). For the time being, radio is a fairly slow medium. Some radios are only 9600 baud, less than what a lot of RS232 interfaces use. Others use 250 Kbps, still slow compared to the 10 or 100 Mbps of wired Ethernet systems.