Lon terminating resistors

[dapper]

I have put together a small network for my own training purposes. I have an Ilon100, Distech EC-67, SLTA-10, Circon VAV UHC-202 and hopefully some Echelon IO modules.
My question is, do I need to buy a $25 terminating resistor or is there another way to do this? I installed some Trane controllers today and they simply use a resistor at the end of there 'LonTalk' comm. network. I think 105 ohm. Will this suffice? Thanks guys.

[jimmyj]

Are you absolutly sure they only use a resistor?
From what I can remember that EOLR "tunes" the channel absorbing reflections ect. the only solid state compoenent that can "absorb" anything electrical is a capacitor and to be sure a resistor. Echelon has a document that discribes the EOLR compoenents and you could make one I guess, but IMO just buy a few you will use them by the hundreds eventually.

[nikko]

For a small desktop network, you're probably fine. Try it and see how the error rate is. If you can talk to the controllers and poll them for real-time values, you're good to go. If the error rate is high, you need to terminate the network.

Niiko

[greg o]

Try it without ant termination at all.
We have some Honeywell Lonspec systems out where we removed all the terminations and the system ran better.

[jimmyj]

Ok,
The system ran "better" can you elaborate please. Did you examine bus trafic with a protocol analyzer and see a scientic, quantifiable improvement?

[crab master]

A small network will work fine without the terminator. Several I know of were put in without terminators - I added them later - and I put in one myself - 10 total Lon stamped controllers and I forgot to put in the terminator. It's been operating fine for over 4 months. It's over 200 miles away, otherwise I would have went back and added it.

[the_dude]

'Tis true. For small networks, you don't really need to use a terminator (it is still good practice though, especially if the network is 200 miles away).

Please refer to Chapter 4 of the following link if you are interested in making your own terms:

http://www.echelon.com/support/documentation/Manuals/078-0156-01G.pdf

[greg o]

Originally posted by jimmyj
Ok,
The system ran "better" can you elaborate please. Did you examine bus trafic with a protocol analyzer and see a scientic, quantifiable improvement?

Non-scientic perhaps, but there were many missing nodes with the terminating resister(s) in place as recomended. We removed them and now have zero problems monitoring the system. Plus before we were getting strange problems with zones and air handlers. Zones that would not heat or cool as needed, plus problems with the economizers. all disappeared after we reomoved the terminations. The system was "flakey" before, afterwards solid as a rock.
Good enough for me!

[dapper]

Thanks for the replies guys. My initial thought was to try to get away without the terminating resistor until I was on the job where Trane spec'ed a 105ohm resistor on their comm loop. That seems to be a cheap solution.
Thanks for the link dude. That terminator is simple enough to make. I will probably try that route

[lonboy]

A TP/FT-10 channel (twisted pair) terminator is not just an end of line resistor, it includes a capacitor or two depending upon the channel topology. A single terminator is required for free topology. Bus topology requires a terminator at each end. I know, this stuff just works, - who needs em? Hell, I've seen it work on thermostat wire! Just not very well! So, if you are going to grow your LON and you want to keep it green (sorry, I can't help it)- you should be keeping the packet error rates as low as possible and this means using the right wire and the right terminators installed in the right places. And if you are doing LON without a protocol analyzer - you're shooting in the dark - like troubleshooting without a meter. Read chapter 4 in the FTT-10A user guide http://www.echelon.com/support/documentation/manuals/default.htm#OEM - it even gives the spec's so you can make your own Arnold and save the 20 bucks they cost. (here in
Cali - we call him the Governator)
Cheers,
lb