You are not registered yet. Please click here to register!


 
 
plc storereviewsdownloads
This board is for PLC Related Q&A ONLY. Please DON'T use it for advertising, etc.
 
Try our online PLC Simulator- FREE.  Click here now to try it.

---------->>>>>Get FREE PLC Programming Tips

New Here? Please read this important info!!!


Go Back   PLCS.net - Interactive Q & A > PLCS.net - Interactive Q & A > LIVE PLC Questions And Answers

PLC training tools sale

Reply
 
Thread Tools Display Modes
Old September 12th, 2018, 06:04 PM   #1
TheWaterboy
Lifetime Supporting Member + Moderator
United States

TheWaterboy is offline
 
TheWaterboy's Avatar
 
Join Date: May 2006
Location: State of Denial
Posts: 818
ML1400 read PLC5 through Serial Radio - not so much...

First time trying this particular combo. ML1400 and PLC5 over radio.
Initially I used 2 PLC5's and set them up to talk across the radio link and that worked just fine. So that clears the radio config from the equation

I set up MSG in the ML1400
This Controller:
Channel 2
PLC5 Read
N7:100
10 elements

Target Device:
timeout 5
N7:200
Node addr 35 (dec)
Local

2 errors depending on Channel protocol selection

Channel 2 set for DF1 Radio Modem:
Errors with message timed out in local processor

Channel 2 set for DF1 Full Duplex:
Error Hex 7 Target Node does not respond DF1 DLE Ack/NAK timeout . . .

ON difference I can see from the PLC5 and the ML1400 are
Channel in PLC5 is System Point to Point
There is no "typed" read in the ML1400

what am I not getting right here? Is DF1 Full Duplex right when radio is Simplex? (one freq for TX and RX)
  Reply With Quote
Old September 12th, 2018, 06:41 PM   #2
Ken Roach
Lifetime Supporting Member + Moderator
United States

Ken Roach is offline
 
Ken Roach's Avatar
 
Join Date: Apr 2002
Location: Seattle, WA
Posts: 14,285
Double-check the PLC-5 serial port error checking mode. The PLC-5 uses 1-byte BCC by default, while the MicroLogix uses 2-byte CRC by default.

To my knowledge the PLC-5 does not support the "DF1 Radio Modem" variant, so stick with DF1 Full Duplex.

Whether or not DF1 Full Duplex will work depends on how fast the radios turn around and how fast the "slave" device answers.
  Reply With Quote
Old September 12th, 2018, 06:52 PM   #3
TheWaterboy
Lifetime Supporting Member + Moderator
United States

TheWaterboy is offline
 
TheWaterboy's Avatar
 
Join Date: May 2006
Location: State of Denial
Posts: 818
Hi Ken
Checked error correction, set both to CRC and also tried both to BCC. Still failed.
Slave device . . . meaning the PLC5 or the other radio?
  Reply With Quote
Old September 12th, 2018, 07:29 PM   #4
TheWaterboy
Lifetime Supporting Member + Moderator
United States

TheWaterboy is offline
 
TheWaterboy's Avatar
 
Join Date: May 2006
Location: State of Denial
Posts: 818
Foung this on KB
.Must be a null modem cable between the 25 pin PLC5 serial port and the Micrologix serial port.
.Could use the 9 pin or mini round din on Micrologix side.
.The baud rates must match along with the error checking and you must change the node number on the Micrologix to 0. Don't use the default or the message will not work.

Didn't know about the node number being zero. this precludes having multiple PLCs on the same radio network...
  Reply With Quote
Old September 12th, 2018, 08:15 PM   #5
OkiePC
Lifetime Supporting Member
United States

OkiePC is offline
 
OkiePC's Avatar
 
Join Date: Mar 2005
Location: ENE of Nowhere Oklahoma
Posts: 9,982
I think the quick and dirty fix is to slap another 1400 near the PLC5 with one serial port on the radio network using DF1 radio protocol, and use its other serial port to talk to the PLC5.
__________________
It's not all the variables I am most concerned with, it's the undiscovered constants.
  Reply With Quote
Old September 12th, 2018, 08:41 PM   #6
TheWaterboy
Lifetime Supporting Member + Moderator
United States

TheWaterboy is offline
 
TheWaterboy's Avatar
 
Join Date: May 2006
Location: State of Denial
Posts: 818
If there is really a problem with this I'll replace the PLC with something better suited to comms. This location will be a master radio poll. I'm just testing the waters now.
  Reply With Quote
Old September 12th, 2018, 10:08 PM   #7
Ken Roach
Lifetime Supporting Member + Moderator
United States

Ken Roach is offline
 
Ken Roach's Avatar
 
Join Date: Apr 2002
Location: Seattle, WA
Posts: 14,285
Quote:
Must be a null modem cable between the 25 pin PLC5 serial port and the Micrologix serial port.
A "null modem" cable is appropriate if there are is only wire between the two serial ports.

Because of the pinout differences between DB25 -> DB9, this is generally 2-2. 3-3, 7-5.

If you have radio modems in between the two controllers, then you connect them in the appropriate way to the radio modems.


Quote:
Could use the 9 pin or mini round din on Micrologix side.
.
The DB9 port is Port 2, and the round Mini-DIN port is Port 0. Make sure you are connected to the correct one.


Quote:
The baud rates must match along with the error checking and you must change the node number on the Micrologix to 0. Don't use the default or the message will not work.
This is if the MicroLogix is the originator of the message, and you are using DF1 Full Duplex.

If you are using DF1 Half Duplex, the configuration changes.

You mentioned only having one PLC on each side of the link, which is why I advised about DF1 Full Duplex.
  Reply With Quote
Old September 13th, 2018, 10:07 AM   #8
TheWaterboy
Lifetime Supporting Member + Moderator
United States

TheWaterboy is offline
 
TheWaterboy's Avatar
 
Join Date: May 2006
Location: State of Denial
Posts: 818
The Duplex is the only area in question.

To my understanding of Police (or voice) radio , Full Duplex comms takes 2 frequencies, TX and RX so that both ends can talk at the same time or so the data or voice can the be repeated across hilltops.

That's not how my current system or this new one is configured. So I'm thinking that must not be what full duplex means as it pertains to this setting.

Master and Slave are the only half duplex options. So if I choose that option , with multiple hilltops covering the area I will still have multiple masters talking to the slave radios in their area.

I need a better understanding of this.
  Reply With Quote
Old September 13th, 2018, 12:43 PM   #9
Firejo
Member
United States

Firejo is online now
 
Firejo's Avatar
 
Join Date: Jun 2008
Location: Redmond, WA
Posts: 1,018
Quote:
Originally Posted by TheWaterboy View Post
The Duplex is the only area in question.

To my understanding of Police (or voice) radio , Full Duplex comms takes 2 frequencies, TX and RX so that both ends can talk at the same time or so the data or voice can the be repeated across hilltops.

That's not how my current system or this new one is configured. So I'm thinking that must not be what full duplex means as it pertains to this setting.

Master and Slave are the only half duplex options. So if I choose that option , with multiple hilltops covering the area I will still have multiple masters talking to the slave radios in their area.

I need a better understanding of this.
Most modern day serial radios will operate full duplex at least that's how it appears to the attached equipment (in this case the PLC's). They use transceivers that will switch from transmitting to receiving at such a high frequency rate the serial protocol never sees anything but a full duplex path.
What radios are you using?
__________________
Go Hawks!!!
  Reply With Quote
Old September 13th, 2018, 02:21 PM   #10
TheWaterboy
Lifetime Supporting Member + Moderator
United States

TheWaterboy is offline
 
TheWaterboy's Avatar
 
Join Date: May 2006
Location: State of Denial
Posts: 818
Using GE MDS radio
  Reply With Quote
Old September 13th, 2018, 03:36 PM   #11
Firejo
Member
United States

Firejo is online now
 
Firejo's Avatar
 
Join Date: Jun 2008
Location: Redmond, WA
Posts: 1,018
That's kinda a broad brush (MDS makes/made a lot of radios) however given that it worked when it was both PLC5's it's probably not a half/full duplex thing. I would first connect the PLC's to each other without the radios and make sure that the protocol settings and port setting are all correct. Once you've got that working then put the radios in place. Keep in mind that cabling between the PLC's without the radios and with the radios will be different. Your best bet is to get a pinout of each devices serial port and make sure that you are going from the TX (transmit) pin of one device to the RX (receive) pin of the other (ground goes to ground). It's also worth noting that the TX and RX pins on a DB25 connector are the opposite than they are on a DB9 so a "straight through" cable will swap pins 2 and 3. A "Null" 25 to 9 cable will have pin 2 going to pin 2 and 3 to 3.
From everything I've read on this post I'm guessing you're having a cabling issue probably on the MicroLogix side.
__________________
Go Hawks!!!
  Reply With Quote
Old September 13th, 2018, 03:45 PM   #12
TheWaterboy
Lifetime Supporting Member + Moderator
United States

TheWaterboy is offline
 
TheWaterboy's Avatar
 
Join Date: May 2006
Location: State of Denial
Posts: 818
Sorry - Radio is a GE MDS MCR Ethernet/Serial radio

I think we found the problem, but I'm setting up some more testing at the moment so we can drive around the area testing coverage.

These are set up as Access Point and Remote. Multiple remotes shortly.

Seems the Remote was missing the Access points IP address. Guess that wasnt written to NVram before unplugging.

I have them, both on the bench now and they are talking. Still not convinced.

A further caveat discovered... the MSG in the PLC will complete (DN bit set) as if its is satisfied, yet no data was transmitted (or read depending) to the other PLC . Its like the Radio satisfies the PLC before actually completing its job. That has not helped.
  Reply With Quote
Old October 2nd, 2018, 05:56 PM   #13
TheWaterboy
Lifetime Supporting Member + Moderator
United States

TheWaterboy is offline
 
TheWaterboy's Avatar
 
Join Date: May 2006
Location: State of Denial
Posts: 818
Update - Have GE Support on the phone with a sniffer in the traffic and a modbus simulator on both sides - appears that these radios are dropping part of message for no good reason.

Possibly unrelated: Using the L61 and BCC will cause the sniffer to show an error that the destination address data from the slave back to the master is empty. CRC doesnt do that - messages complete with either mode from the perspective of the PLC ladder.

Perhaps that BCC error is the equivalent of the missing data that GE support is noticing. Or it just clips the message too soon.

Interesting times.
  Reply With Quote
Old October 2nd, 2018, 07:17 PM   #14
Firejo
Member
United States

Firejo is online now
 
Firejo's Avatar
 
Join Date: Jun 2008
Location: Redmond, WA
Posts: 1,018
Why are they using a Modbus simulator? Modbus RTU and DF1 are very different and will behave very differently across radios (with DF1 being much more forgiving). Unless the radio was specifically setup to deal with Modbus RTU it will drop packets. Having said that if the radios are setup to deal with Modbus RTU, DF1 will not be happy.
As to error checking, I have found in the past the BCC error checking does not work well on a wireless network. I would use CRC.
__________________
Go Hawks!!!
  Reply With Quote
Old October 2nd, 2018, 07:31 PM   #15
TheWaterboy
Lifetime Supporting Member + Moderator
United States

TheWaterboy is offline
 
TheWaterboy's Avatar
 
Join Date: May 2006
Location: State of Denial
Posts: 818
Modbus Exactly, we didn't want forgiving, we wanted solid.

We wound up clearing the radio, re-setting all the configs, set the Mcast Address from 254.100.0.5 to 254.0.0.0 (on request from support... not sure about that .0 address...)

Modbus started working properly, Moved back to the DF1 without changing the radio at all and comms worked properly.
Must have been a bad bit in the config from a solar flare. No definitive cause...

Now we create a hop (Remote -> AP -> Remote) and see if it will traverse it. Film at 11.

But I will say that the books and the tutorial videos for this model are both wrong in many places. The instructions work for the NX series - but not this model.
  Reply With Quote
Reply
Jump to Live PLC Question and Answer Forum

Bookmarks


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Topics
Thread Thread Starter Forum Replies Last Post
Ethernet PLC to Serial Radio jfritz8 LIVE PLC Questions And Answers 8 September 6th, 2016 04:37 PM
burn ethernet pc card while connecting to ml1400 parralle with a serial cable. Jeff23spl LIVE PLC Questions And Answers 6 August 18th, 2015 02:57 PM
Serial event on ml1400 series-a scadagetco LIVE PLC Questions And Answers 11 March 30th, 2013 11:53 PM
radio shack usb serial cable rexracer LIVE PLC Questions And Answers 4 February 9th, 2012 11:47 PM
CLX - PLC5 via serial port? Vladimir LIVE PLC Questions And Answers 1 February 3rd, 2005 01:05 AM


All times are GMT -5. The time now is 04:07 PM.


.