AB DF1 Half Duplex Wireless System

[DMC]

Hi everyone. Happy New Year. I'm a newbie to this forum as well as to AB.
I'm working on a Half Duplex DF1 wireless system that uses 3 AB Micrologix 1200C PLCs (Slaves).
The PLCs are interfaced to a RSView station (Master).

I am using 4 MDS 9810 serial radios of which 1 is a Master, 1 a Repeater/Slave and the other Slaves. The process is to monitor 2 pumping booster stations (1 feeds uphill to the other) and on to a tank on top of a mountain which provides potable water to the community below.
The tank level, motors status, alarms etc information is then sent back to the Township building where the RSView station is setup as the Master. The system runs at 38,400 bps.

I am getting -95dB from Master to Repeater and -90dB to the other sites from the Repeater.

My problem is that I am having a hard time tuning the system. I am experiencing "graying out" on my motor graphics (normally red or green)to indicate which pumps are running at the booster stations.

I haven't been able to get the system running without timeouts, and a lot of retries and it's very frustrating at this point. It works okay, but when I check on it the next day I have a bottleneck of 80-90 bytes in the message queue.

Here are my protocol settings:
ACK timeout: 500mS
retries: 3
packet timeout = 40 seconds
delay after xmting packet 2mS
retransmission delay =0


I am polling using in sequence standard polling all stations are being priority polled, duplicate packet detect is on.

If anyone has any experience with using DF1 Half duplex Master/Slave in this way, would you suggest some settings for the Master in this application.

Thanks

 

[SNK]

I don't know dude. What is the make of the repeaters and the communication devices that you are using? You are connected serially, as you indicated in your post.
I am more familliar with Prosoft stuff. If you are going AB, use Prosoft.
I have attempted using 3 Micros in a link on ethernet also, even on a SCADA system, and the results are daunting if there is a lot of traffic.
Go to the PROSOFT webpage and do a little more digging.
You might be lucky to find someone out there with a little more experience.

Good Luck!

 

[Ken Roach]

here come the questions

There are a lot of variables involved in setting up a half-duplex network, and most of them are dependent on the modems you are using, how much data you are requesting, and how fast you want it.

Tell us more !

Those settings you posted are only a handful of the settings for a DF1 Half-Duplex Master in RSLinx. You should make an RSLinx Backup file (*.RSX), compress it into a ZIP file, and post it to the Forum. That will be easier than using screenshots or listing the settings.

I'm also curious about the physical settings of the modems; are they using handshaking ? Are there delay settings that the modem makers recommend ?

The settings in RSView matter, too. I presume this is RSView32: are you using a Direct Driver, or an OPC driver ? What is the polling rate, and how much data are you requesting from each slave node ?

 

[Guest]

Wireless Half duplex system

Hi all.

Thanks for your replies.

The serial radios are 900MHz Spectra-920's from Microhard Systems not MDS radios.
(http://www.microhardcorp.com for spec details)

I got the system to work by configuring them to use an over the air rate of 230kbps and setting the retries on the Master to 10 and 5 on each of the Slaves and Repeater.

I am getting about 2.8 to 3.5 packets per second send/receive.

I have the RSwho poll settings as follows:

Poll Timeout: 10000mS
Poll known stations every: 100mS
Maximum concurrent packets: 3

Is it right to assume that the RSwho applies only to browsing to indicate for tuning what actual data might represent through the system? The autobrowse feature should be turned off when the system is deployed to avoid useless bandwidth waste I believe.

With regard to the timeout setting on each of the Micrologix 1200's? Currently they are set to (20ms x 3000).
How does the timeout on the PLC slave driver themselves work?
Should they match the Master driver timeout settings?

The Rslinx settings are set at default except for the Retransmission wait time which is 0.

I am polling by the polling list configuration which has the slaves in priority and the repeater in normal.

38.4k and everything else is default, I will get a .rsx file.

I would have loved to use DF1 radio modem driver which comes with the Micrologix 1200's, but there is no driver for DF1 Radio modem MASTER in RSlinx.

I was surprised that I could not find anything on a setup like I have.
(RSview as Master to 3 Micrologix 1200's (1 Repeater and 2 as Slaves off that Repeater).... even AB couldn't tell me anything really.

The following AB document helped explained how DF1 works.....

www.ab.com/support/abdrives/1203/serial_communication/3302.pdf

Thanks again

DMC

 

[Bitmore]

RTU Engineers without at least a radio technicians license from the FCC scare me.

I have one.....KC8WIK it's called a call sign and it is printed on the front of my Technician radio license.

ps: sorry Ken it's just me!

 

[DMC]

scared FCC fellows

Bitmore,

Thanks for the help you never gave....

This was not a radio issue so your comment is unappreciated.

As far as a radio license for unlicensed radio systems, explain how that would of helped you in this case?

Your negative attitude and those like you is the reason others don't post in this forum.

Have a great weekend.

DMC

P.S. Thanks Ken and Carlen

 

[Bitmore]

If you want negative just look at your post.
I just added my opinion, you added yours.
Peace be with you my fellow human.

 

[DMC]

opinions

Your opinion makes 0 sense

explain how being a HAM would help?

DMC
You sound like a very unhappy person with personal issues and illusions of grandeur.

Good night and God bless

 

[Bitmore]

You figure it out

 

[Fred Floggle]

I am not sure I can help you without seeing the setup but....
I'd be interested to know what you had to pay for the modems- they look nice gear .

 

[DMC]

price for Microhard radios

I know we bought them direct from Microhard Systems and that the price was probably lower than the MDS radios.

We did a demo with option to purchase as we hadn't used them before, but heard good things about their modems.

They work nicely and the remote diagnostics through the separate diag port is invaluable when setting things up, they even helped solve a cable/connector problem as they have built in VSWR measurement.

I'm sure they would quote a price through the email request on the site.

DMC

 

[rsdoran]

I agree with DMC, there is no need for a radio tech license for systems that dont require it.

I have an FCC license but I am not a HAM (that term does seem to apply) radio operator so do not have a call sign. Morse code also was not necessary for my license.

Like anything licensing is relative to the application, in this case isnt needed.

The problem seemed to be more on configuration/settings than an issue with the radio/modems. I would like to have been involved in this application because I havent had an opportunity to use any wireless, ethernet or radio, in a plc system.

Will be looking at all the info offered on this subject.

 

[DMC]

A long overdue update

Well, I came across this and figured I'd update it.

The RSview as Master to 3 ML1200 slaves through slave and repeater radio modems did end up working, after a lot of time spent with timing adjustments.

The system did have hiccups and did strange things over the course of a year.
In the end we installed another ML1200 at the Master site and configured it to use DF1 Radio modem and things have been fine since with the system.

Sorry for the 4 year late reply LOL.

DMC