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Got PoE in your Christmas stocking?

  
  

Dear Friend and Subscriber:

Another Christmas season has zoomed up to our doorstep. School plays, concerts and late night shopping consume the evenings -- and I’ve found a few things to keep me busy at the office as well. All the chaos will come together with a few days of family celebration.

Christmas is also a leading indicator that another Midwestern winter is settling in, with no global warming-induced relief in the forecast. I barely lasted a day into December before I escaped to the desert Southwest for some warm air and R&R. This winter I’m vowing to slip off to someplace warm and sunny every month. So, if you happen to be somewhere warm, I may very well be coming to see you. In Minnesota? When Spring’s just around the corner, call me then.

Did you feel a slight disturbance in the force last week? That was me. It may get me banned from some engineering circles, but last week I fully succumbed to the Apple eco-system. It started innocently enough, with a little iPod to accompany me on runs. Then an iPhone ousted my Blackberry. And now the conversion is complete, as I’ve traded in my aging Dell for a racy little MacBook.

Love ‘em or hate ‘em, every engineer can learn something about product design from the Apple guys. They sure know how to make things simple.

On the simple theme, I had a couple of calls last week that got me noodling about Power over Ethernet. PoE is a great example of a simple idea that can simplify your life, and it’s picking up momentum in more and more applications. But, like most commercial technologies, PoE wasn’t purpose-designed for rugged environments. I've put together a quick PoE video to highlight some of the PoE challenges that you might run into and show you how to solve them when you take PoE out of the IT closet.

Got six minutes to spare? Check out the video for yourself.

Or, want to jump right to a few great PoE solutions?

Ever need to install a PoE switch in a rugged location? Vibration, heat, cold and/or lots of noise-causing equipment or power cables nearby? You need the EIRP305-T. It’ll give you 5 PoE ports and has survived the engineering test gauntlet of snarky compliance tests for rugged environments.

Got heavy-duty networking requirements? Check out the 10-port managed PoE switch that also includes two Gigabit SFP ports for a backbone or ring connection.

Coming up short on power? Straight PoE pumps out about 15 watts per port. When that just won’t do, PoE+ ups the ante and gives you 25 watts of power per port. Enough for PTZ cameras, high power radios and all kinds of other devices that you may want to install in a location that doesn’t have access to AC power. The EIRHP305-T gives you 5 PoE+ Ethernet ports, each pumping out up to 25 Watts.

And what about power supplies? It’s always tweaked me that you have to feed most “industrial grade” PoE switches 48VDC. I don’t know about you, but I hardly ever see an installation that has an existing 48V rail. The EIRP305-24V-T solves that problem by supporting a 24VDC power input -- no need for a special 48V power supply.

What out-of-the-ordinary PoE applications have you run across? Talk back on the blog.

And, most importantly, have a very Merry Christmas!

Mike Fahrion

Comments

Mike, 
 
Thanks so much for your readable, funny, and technical notes each month. AND for wishing us all a Merry Christmas, rather then the PC Happy Holidays. 
 
 
 
Merry Christmas to you and your family.
Posted @ Tuesday, December 20, 2011 5:38 AM by Dan
Mike, 
 
First of all, thanks for the entertaining and intelligent emails. I just wanted to remind you that not everyone who operates in rugged environments uses 24v. As a telcom provider in rural Iowa- everything we use is -48VDC, and will continue to be for the foreseeable future. Please offer more -48v options! 
 
Regards, 
 
Jared
Posted @ Tuesday, December 20, 2011 9:25 AM by Jared
Great point Jared - you're right that 48V (and -48V) typically shows up anywhere you've got a battery backed system - Telco and Power Substations are two common ones. We've got lots of products that do support 48V, but not every 48V product is ok for -48V - if in doubt check with Tech Support to be sure the power ground is DC isolated from other ports and chassis ground.  
 
Fellow Iowa native, 
-Mike 
Posted @ Tuesday, December 20, 2011 2:12 PM by Mike Fahrion
Interesting about you succumbing to the Apple environment. I have been in that realm since 1985. However, it can have challenges when doing the kind of work you often do. It would be interesting for you to post in your blog the problems and challenges you encounter with the Apple environment and how you work through them. 
 
Happy Holidays!
Posted @ Tuesday, December 20, 2011 2:47 PM by Jim G.
Mike,  
Merry Christmas to you too. 
 
When you talk about PoE, I had an idea for you. Here in the industrial communications environment where I live, home-running Ethernet CAT 5 cables from each RJ-45 equipped device to a central switch gets to be a rat's nest. Especially when compared to legacy 485 protocols that let you daisy-chain one cable to all devices.  
 
What if you made a tiny 3-port PoE switch and built it so that it was lightweight enough to hang on the cable and create a tap to feed to an Ethernet device? I drew something of what I was thinking and put it here: http://pps2.com/files/bb/3P-PoE_switch.png  
 
If the switch was made small and lightweight enough that it just hung on the cable without supports (like a splice/tap), installation would be simplified. 
 
I figured that such a device would already exist, but maybe I just haven't searched enough. What I did find are lots of 3-port switches, but they need to be DIN rail mounted or are separately powered or they are too big to hang on a cable and so would need to be mounted. 
 
By looping the cable back to a switch that understood one of the fast spanning tree protocols out there, you could build a self healing loop that would be as easy to wire as the old twisted pair networks but with all the benefits of UTP based Ethernet. Our Ethernet devices (at least) don't have a ton of data and latency isn't an issue. In my world, it is more about pushing Ethernet closer to the device and reducing the need for gateways and protocol converters. 
 
Thoughts? 
 
Dave 
Posted @ Tuesday, December 20, 2011 3:16 PM by Dave
Dave - that makes a heap of sense to me. While it introduces potential failure points vs. home run or the simple days of 485 multi drop, the ring redundancy eliminates the risk of single point of failure taking everything down. Some cascading PoE concerns but the way that technology/power levels are progressing it's likely solvable. Let me noodle on this a bit! 
 
 
 
Jim - good idea - I'll track and post some notes on the conversion experience. So far some small hurdles but no roadblocks. 
 
-Mike 
Posted @ Wednesday, December 21, 2011 1:22 PM by Mike Fahrion
Mike, check out Wi3's new networking offering which uses standard coax and Moca. Solves a lot of the PoE problems. 
 
www.wi3inc.com
Posted @ Tuesday, December 27, 2011 12:56 PM by Vince Blehl
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