Tuesday, April 25, 2017

Auto-Negotiation Testing Procedure


The purpose of this guide is to determine a device’s auto-negotiation abilities using an oscilloscope.

Equipment used in this test:
  1. RIGOL DS1054Z - 4 Channel Oscilloscope
  2. Siemon MODAPT- 8pin “banjo”

Connecting the Oscilloscope
  1. De-energize the device under test.
  2. Connect a copper patch cable (Cat5e or better) to the device under test.
  3. Using a “banjo” as shown above connect probe to pin 1 and ground to pin 2.
    1. If no bajo is available a patch cable with a standard RJ-45 Male connector on one end terminated using TIA-568B can be used. Strip back the other end of the cable exposing the 4 pairs of conductors. Strip back 1” of insulation on the wh/orange and orange conductors. Connect the probe to the wh/orange and ground clip to the orange conductor.
  4. Energize the device under test

Setting up the Oscilloscope

Initial settings:
5ms/div
2V/div
Trigger-2V (auto on most scopes will work best)
This will show the Auto-negotiation pulses also known as Fast Link Pules (FLP). This is shown in the screenshot above.


Analyzing FLP
After capturing a set of FLP’s, change the settings on the oscilloscope.
200us/div
2V/div

Note the 17 clock pulses. The time between each clock pulse is 125µs +/-14µs. These will be accompanied by 16 data pulses. These 16 data pulses represent one 16-bit word. The presence of the data bit represents a binary 1. The lack of data pulse
represents a binary 0.  We can analyze the data bits to see what the device under test is advertising as it’s abilities. The screenshot above represents a device that is capable of 100Mbs Full-duplex.

Auto-negotiation uses the greatest common denominator between each side of the link to establish the best possible connection.

If you have any questions, please contact:

Shawn White - Shawn@teamtech1.com

Tuesday, March 14, 2017

PROFINET: Good, Bad, or Ugly?

Is PROFINET right for your application?

Image result for good bad ugly

The short answer, maybe. There are so many options out there right now, it's hard to choose the right communications protocol. Hopefully, this article will help shed some light on to PROFINET, and whether it could be a good fit for your applications.

There are 3 main criteria that must be considered when choosing or designing an industrial communication network; performance, installation, and availability/support. All items that you may want to consider can be boiled down to one of these items. Let's start from the top and work our way down.

Performance

The performance of any network is important, but in an industrial application, it can be extremely important. The requirements may vary greatly. If you are only wanting to turn on or off a light indicating the status of a device, speed of the network may not be all that important. Latency of 300-500ms probably won't be an issue. However, if you are performing precision motion control 300ms is unacceptable. One of the great things about PROFINET is that it has several different ways to accomplish communication depending on the requirements. If you need precise and ultra-fast communications PROFINET is for you. With some of the best update times available, PROFINET offers it's Isochronous Real-Time (IRT) protocol that can be seen in this video from Siemens.  I'll spare you the exact details (although if you are interested, feel free to email me here), but the idea is that it uses a time-sync feature and skips multiple layers in the OSI model to speed up transmissions. From simple motor control to complex syncing operations PROFINET has the flexibility you need.

Installation

Let's face it if it's hard to install you probably don't want it. PROFINET, like it's predecessor PROFIBUS, is extremely easy to install. Quick and efficient installation of industrial communications networks is essential. PROFINET fits the bill. From the easy to install hardened connectors (seen here) to the robustness of the cable, PROFINET is designed with the installer in mind. Installation guidelines must be followed, however, to ensure proper performance. It's never a good idea to run communication cabling with unshielded VFD cabling (I've seen it done!) With support for Fiber and copper, PROFINET can be easily implemented.

Availability & Support

Image result for support Possibly the most important factor of any installation in an industrial setting is the support and maintenance of the network. PROFINET is believed to make up approximately 8-9% of the overall field control networks which equates to 23% of the industrial ethernet networks currently installed according to IEN. What's this mean for you? As one of the most common industrial networks used, devices and components are readily available. Also, PI (Profibus and Profinet International) established a strict guideline required for certification of devices. This certification process is mandatory for any PROFINET device carrying the PROFINET name. Certification of devices ensures that the device has been tested and works according to the specifications set forth by PI. This helps make the task of choosing devices easier, knowing that if it carries the PROFINET certification it will work with your PROFINET network. PI also offers a network of certified engineers and installers to make support and troubleshooting an existing network as simple as possible.

The Bottom Line

For most applications, PROFINET is a great choice, but it's important to look at the criteria you require for your network. If you find yourself with questions regarding PROFINET capabilities or compatibility, please feel free to reach out to our team here. We are dedicated to providing your facility with the most reliable, secure, and profitable network possible. We understand the challenges faced by many industrial environments and are certified by PROFINET, Hirschmann, Panduit, & Belden, and have a BICSI RCDD on staff. We offer emergency services and FREE consultations. You deserve more up-time and we GUARANTEE it!