Crestron Systems - Programming? - Page 4

The shield is electrostatic, like a Faraday cage.

The twisted pair ensures that induced electromagnetic interference couples to both conductors equally, for effective cancellation at the differential receiver.

Differential signalling doesn't require a ground reference.
A telephone line has no shield or ground reference for the AC (audio) signal.

And the Faraday cage is used to reduce EMI.

Thanks for the help, Sam.

No, electrostatic interference.

Found a good reference that explains electrostatic and EMI. Chapters 2 and 3, from a recording studio design site.

http://members.ozemail.com.au/~tabbler/GndRule/GndM02.html

The foil shield is to reduce electrostatic interference, and the pair twists are to reduce EMI.

Now I think I've got it, with the explanation.

Sounds like youze guys are still up in the air about what to use for your own cresnet, so I'll tell you of my experimentation.
My whole house was wired with cat5e before I decided to get involved in a Crestron system. I have tried this both ways and have had no problems either way. I have used a twisted pair for each conductor (all four) and I have used a twisted pair for +, one pair for - and one pair for signal, leaving one pair for a spare. My system has been in for years now with no problems.

"So, then what's the purpose of the shield, for the Cresnet control pair?"

Just because the DC in the cresnet doesn't cause EMI, doesn't mean you didn't pull the wire in close to a AC motor feed or something.
That said, I have some of that cat5e I spoke of earlier pulled through the same chase as a 50 amp feed for my pilot arc plasma cutter and AC/DC TIG welder. My wife has not complained of any TP problems associated with that pull when I'm out working in my shop.

I bought a TP for learning programming. I honestly don't plan on installing it, but who knows what I'll eventually end up doing.

On the test bench, I'll use 18/2 x 2. For the 2 feet, twists (and probably shield) won't make a difference.

My only obstacle is free time.

Google "differential signalling" for the answer , it's like you're not even reading this thread.

Would be also good to google common mode rejection ratio (CMRR) while you are at it to realize balanced interconnect doesn't mean you are immune to noise . There is a reason shielded twisted pair cable also exists.

He's goading you, Ace.

Thank you, Amir. I've spent enough time reading about the esoterics of RS485 design, common mode noise rejection, foil shielding, and electrostatic interference. It's interesting, but not too relevant for practical purposes.

Tell us about it then

I am not going to do that. The guys are trying to learn about programming Crestron. It has nothing to do with arguing about shield vs not when they are just building a test fixture. Let them be please.

It's true that I have not kept up with this thread from start to now but if you read all of page one including the title of this thread you will see that this is a learning programming thread not how wire design works on paper. I have a friend who claimes to be able to tell the difference in sound with his speaker wires elevated off the floor. One of these days I'm going to challange that with blind side test, a switch and a roll of 12-2 romex.

Now if we are still talking about hooking up a test system on the bench, you could straighten out four coat hangers for your Cresnet and it will work just fine as long as they are not touching.

Hi all,

Firstly thanks for sharing your experience and advice.

I also am interested in a career change and am wanting to get into the home automation\control programming line.

I have done a few systems successfully over the past 5 months with Axium and Elan products.

I realize that Crestron is the industry leader in this regard and would like to get up to speed. I am aware of the steps to begin.

1. Subscribe to the Crestron yahoo group.
2. Sign up for training.
3. View the intro videos on the Crestron site.
4. Download the programming software.
5. Look through the demo programs.
6. Skip anything that says System Builder/SB.
7. Get your hands on an MC3 controller.
8. Play with it.
9. Attend training.

Before i dive head first and get this ball rolling i would like some advise please. We have a few Crestron products @ the shop and was wondering if they would be a good place to start.

http://www.crestron.com/resources/product_and_programming_resources/catalogs_and_brochures/online_catalog/default.asp?jump=1&model=st-1700c

http://www.crestron.com/resources/product_and_programming_resources/catalogs_and_brochures/online_catalog/default.asp?jump=1&model=cnx-pad8a

http://www.crestron.com/resources/product_and_programming_resources/catalogs_and_brochures/online_catalog/default.asp?jump=1&model=cnmsx-pro

Any advice in this regard would be greatly appreciated.

Most importantly, you'll need access to Crestron software. Crestron equipment cannot be programmed without the sw.

What's with the terminal blocks for composite and Svideo? We have standard industry connectors for these - Svideo standard 4pin miniDIN and RCA or BNC for composite.

Y/C (S) was often run as two-wire for the best quality over distance. On larger equipment it was common to have two BNCs for Y and C (S-Video) plus a BNC for CVBS (Composite). I imagine that they did this to save space. Plus it's a lot easier to terminate using screw terminals than field-terminating a bunch of BNCs.

If it was for 'best quality' they would have used BNC's and 75 Ohm coax.

Agreed, that's my point.