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Cool Stuff: Fieldbus Finder by Sick Sensors

Sick sensors has a really cool web page showing their products sorted by supported fieldbus.  It’s simple:

  1. Find the fieldbus you’re interested in; choices include CANOpen, DeviceNet, EtherCAT, EtherNet/IP, HIPERFACE, IO-Link, Modbus TCP, Profibus DP, Profinet, PROFIsafe, and SSI.
  2. Find the component type you’re interested in.  What’s available varies with the fieldbus; for example, only measurement and feedback sensors are available for the SSI and HIPERFACE encoder buses.
    1. However, the major fieldbuses have a lot of available types, typically including absolute encoders, bar code scanners, 2D code readers (for Datamatrix and such), laser measurement, linear measurement, light curtains, network gateways, RFID, safety controllers, safety laser scanners, and hand-held scanners.
    2. Sometimes, adding fieldbus functionality requires a gateway module, or an external communications module.  From a glance, it appears most safety communications (e.g. to safety controller) and most EtherCAT communications require a gateway — and those gateways can be pricey.
    3. Still, Sick’s level of fieldbus support is impressive.
  3. Then a new tab appears with search results for the component type, already filtered by fieldbus type.

September 3, 2013   No Comments

Cool Components: ACS EtherCAT To Analog Drives

One complaint I have about most proprietary motion control field buses is that the I/O choices available are very limited.  Standard field buses such as CANOpen, Ethernet PowerLink, and EtherCAT have a much better selection of I/O modules as well as a wide selection of drives, but there’s one device that’s hard to find on most motion networks, proprietary as well as standard: an interface to analog servo drives.

Analog servo amps are still important because specialized equipment such as piezo motors can require you to use a custom servo amplifier, which typically has a +/- 10V analog input.  So if you want to use these devices on a network, you’re out of luck — unless you can get a network to analog drive.

The Logosol LDCN is the only proprietary motion network I know of that has drives with an analog output (they are the LS-160, LS-170F, and LS-180).

I’ve only found one company making analog output drives for a standard motion network: the ACS Motion EtherCAT intefaces.  ACS has various models.  The SPiiPlusUDI modules can control 2 or 4 analog servo amps.  The SPiiPlusPDM modules can control 2 or 4 step/dir input drives, including step/dir servo drives, stepper drives, or laser generators.

I think the UDI modules are more useful, but I’m sure the PDM modules can be handy.  For example, if you want to use a proprietary Asian servo motor that has to be used with a proprietary drive that takes step/dir input.

Important note: after I wrote this, I had a discussion with a local ACS distributor, and he said he was pretty sure that the ACS EtherCAT drives and modules will only work with ACS motion controllers (hardware or software).  So, if you’re interested in these modules but don’t want to go 100% ACS, please check first.

May 30, 2013   No Comments

Mixing Industrial Ethernet Protocols

Standard Ethernet is inherently not capable of real time communications, and thus industrial Ethernet protocols that can run on stock Ethernet hardware cannot be real time.  The best they can do is provide synchronization (for example, using hardware or software implementations of the IEEE-1588 Precise Time Protocol).

Of course, coordinated multi-axis motion using distributed Ethernet servo drives need real time communications, but the problem with real time industrial Ethernet networks is that they cannot use commercial switches and maintain good real time behavior.

One solution I’ve seen from several manufacturers is to put a motion controller in the middle.  Instead of directly connecting the Ethernet servo drives to the main industrial network, the drives are connected to a multi-axis motion controller, which then connects to the main industrial network using a different protocol.  The controller receives higher level motion commands, and sends out lower level motion commands over its own, private real time network to the distributed drives.

Similar motion controllers exist for CANOpen (Ethernet or other network in, coordinated CANOpen motion out), but I find the use of multiple Ethernet protocols interesting.  The result is potentially very good: appropriately using the strengths of the different protocols to make the overall automation system better.

I haven’t needed to use of any these yet, since I don’t have a requirement for Ethernet speed or advanced coordinated motion.  However, here are the controllers I’ve come across:

  • Parker ACR9000-EPL series motion controllers.  They can communicate with Ethernet/IP networks, and talk to servo drives using Ethernet PowerLink.
  • Omron NJ series controllers.  They can communicate with Ethernet/IP networks, and communicate with servo drives using EtherCAT.
  • Elmo Gold Maestro motion controllers.  They can communicate with Modbus/TCP networks, and communicate with servo drives using EtherCAT.
  • ACS SpiiPlus controllers (including the soft controller, I believe).  They can communicate with Ethernet/IP networks and talk with servo drives using EtherCAT.


July 25, 2012   No Comments

Fieldbus Book Wars

Notes 4/21/2011: I’ve updated the links and status (but not the chart); both CANOpen books are now available.  Sometime I’d like to revisit field bus books, but it’s not a high priority.

One way of judging programming language popularity is to compare book sales. So I decided to do something similar – see how many books in had the names of popular fieldbuses in their title. I excluded non-English books (German Profibus users get more choices) and standards documents.

Fieldbus In Print Out Of Print Total
CANOpen 0 2 2
Profibus 2 1 3
Profinet 1 0 1
Foundation Fieldbus 1 2 3
Devicenet 0 0 0
Ethernet/IP 0 0 0
EtherCAT 0 0 0
Ethernet PowerLink 0 0 0
Modbus 0 0 0
Modbus/TCP 0 0 0
CC-Link 0 0 0

I wouldn’t choose a fieldbus on the basis of books; for example, many of the fieldbuses have good information available on the web. But it’s interesting to look at the book titles and year of publication:

Apparently fieldbus books do sell: several recent books are already out of print (or otherwise unavailable).


February 20, 2008   3 Comments