MicroLogix to MicroLogix Communication

Hi folks,

I am new here. I am not new to PLC's.

I have very few man hours with AB PLC's (used mostly Siemens and some ControlLogix).

This is the challenge that I have:

I got 2x MicroLogix 1200 PLC's and one PV C600 Screen. I have to make the two PLC's talk to each other using RS232 (has to be RS232) and connect one PLC to the C600 as well.

How can I make this work. What do I need to get to make this work?
The PLC-to-PLC communication has to be RS232 (RS-485 not an option unfortunately), cannot change that.

Thank you!

Eddi

Get crackin.

http://literature.rockwellautomation.com/idc/groups/literature/documents/rm/1762-rm001_-en-p.pdf

Thx, can't sleep anyway, will try this, maybe it will help ...

Could you point to the chapter, the file is extensive and has stuff on ladder logic, I am not that far.

I am looking at communications, but its just ladder logic to do com. Like I said, not that far, need concept.

Thanks.

PitchBlack said:

Thx, can't sleep anyway, will try this, maybe it will help ...

Serious, I will check out the manual and get back, if I have further queries.

Thanks.

Click to expand...

Yea, it seems like a lot, but it's not too back, but you need have a little familiarity with it.

Focus on the DF1 protocol and master/slave details, and the messaging (MSG) instruction descriptions.

HI,

thanks for posting so quick.

I think I found my answer. The DF1 Half-Duplex will probably work. (I will use the MSG block, have used it already in the past).

How would I go about connecting all 3. The serial cables that AB provides are just one device to another. According to the DF1 HD, it can go up to 255 devices, I just cannot get a picture how to hard-wire it ...

Thanks.

I think I figured it out. Please check and validate (or not) if it will work.

I would have to use 2x 1763-NC01 and one AIC+ to make this work.

Setup will be similar as seen here: http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1763-um001_-en-p.pdf on page 81.

Will this work?

Thanks a lot!!!

The 1763 reference manual is only for the MicroLogix 1100, not the MicroLogix 1200. Also, the 1763-NC01 works only on the controllers that have RS485 built into their serial ports, which are the MicroLogix 1100 and 1400. You've specifically required RS-232.

The best way to fulfill the requirements you have specified is to use DH485 protocol over RS-232 using one or two 1761-NET-AIC isolator/converter modules.

If you used just one 1761-NET-AIC, you could connect each MicroLogix 1200 to the RS-232 ports on the 1761-NET-AIC, then connect the DH485 trunk port to the RS422/485 port on the PanelView C600.

If you used two 1761-NET-AIC modules, the system could be more flexible and more symmetrical; each 1761-NET-AIC would use the same type of cable to connect to its 1761-NET-AIC, and you would have a serial port available on each 1761-NET-AIC to connect a PC to.

The downside of this is that it's DH485 protocol, so you will need a 1747-UIC interface to connect a PC. DH485 protocol is also incompatible with modems and radios, which might be why you are requiring RS-232.

If you can give us a little bit more information about the reason for using RS-232 only, and what the distances are between devices, other recommendations might come up.

Be aware also that there is a 2-port "1200R" version of the MicroLogix 1200 that has an HMI/Programming port on the side. Using those controllers might alter your options.

I would use something like Digi One IAP before using AIC, just because they will give you the ability to connect via Ethernet to the serial devices.

Well, this is why I "need" RS-232.

I have 2 tanks (one diesel one used oil) and will be installing a level sensor (APG product) in each tank. The PLCs will monitor the level and turn on a light and sound horn when the level is low. The 2 tanks are approx 200m apart, but the biggest problem is, I cannot pull a wire between them (that would be my preferred way and would use RS-485).

So my idea was, to use 2 XBee as "wire replacement", but the XBee's will not work with RS-485, so it has to be via plain serial RS-232. I am not sure, if it will work, but IMHO it should. I do not need real time msging, just 1 or 2 times a day to update the main PLC to show on the screen.

One PLC will be stand alone with wireless link to main PLC. The main PLC will have the Screen connected to it.

Now, some may think, that the PLC's (specially the ML 1200) are overkill, and that might be true, but we have the equipment already and will not use them anywhere else, so what the heck. Some people just like to use a tank to kill a mosquito ...

I will study the AIC+, at first glance it may do the trick ...

Thanks for the additional application information !

The DH485 protocol won't work over any sort of radio, including an XBee link. It goesn't matter if it's using RS485 wiring or RS232 wiring; the protocol requires timing that no asynchronous radio link can provide.

Is either of your MicroLogix a "1200R" model ?

If you tried to use DF1 Half Duplex, I don't know if the PanelView Component can support it.

If you want to use DF1 Full Duplex, you can only use two devices, so you can't get the PanelView into the mix without having another port.

There might be a role for the DPS1 or DPS2 Port Expander in this... I don't know those devices well.

Neither of the ML 1200 is a "R" version.

This is what I was thinking to do now:

The standalone PLC will connect directly to the XBee.

The "Main" PLC will be connected to a AIC+. The AIC+ will connect to another XBee via the RS-232 port, and the screen will be connected via the RS-485 port.
This way (I am thinking) I should be able to use DF1-HalfDuplex on the RS-232 (radio link) and full duplex on the RS-485.

I am not sure, if it can be configured that way, but that was my though on how I would try it, based on the info I collected so far.

The 1761-NET-AIC is purely a signal converter and signal isolator; it's totally transparent to the protocol. You can't use DF1 half-duplex on one port and DF1 full-duplex on another (and the RS485 port is inherently half duplex anyhow).

The 1747-DPS1 Port Splitter might do the job for you. It allows you to have one full-feature network port (the MSG instructions between the two MicroLogix) as well as one response-only port (which will let the PanelView Component communicate to the MicroLogix).

Thanks Ken!!!

I got a lot of info here. I will read thru the manuals and think this over.

Thanks again!

You could use the 1747-DPS2 Port Splitter.

http://literature.rockwellautomation.com/idc/groups/literature/documents/qr/1747-qr003_-en-p.pdf

Firstly thanks for highlighting these Xbee's. They look perfect for another project of mine

To avoid the issues others have mentioned could you not use 2 Arduinos to take the sensor output from the furthest tank, send it via Xbee and convert it back to an input that the main PLC could read?