Siemens S7-300 and CTI Cryogenics pump

I am in need of some help.

Currently have a CTI cryogenics pump with an onboard and keypad. Management would like to allow our customers to continue monitoring and controlling the cryopump with the onboard and keypad, but also be able to do the same functionality on the plc and hmi.

Is there a way to get the siemens s7-300 to communicate to the pump through ethernet, or serial from the pump to ethernet on the plc?

Any advice or anyone who has successfully made the plc and pump communicate let me know.

Contact the pump manufacturers. They will tell you straight about this

I contacted CTI and they were not very helpful.

I have never attempted to create a file in the PLC that handles ASCII and communicate over RS232 and was just looking for help from anyone who has attempted a very similar project.

Interested too

I have a Parker Compumotor SX drive that speaks ASCII and would be interested in communication through a PLC, HMI in addition to the Stand alone PC to Device RS232 connection.

I suppose, this comes down to PLC to ASCII communication.

As a new guy, I have no idea. But would like to know about possibilities.

Knowing what to ask is always difficult when starting in. ;-)

Siemens has a couple I/O cards designed for ASCII data over a RS232 link. You can download the FBs to Send/Receive data and then you have to configure the cards and DB for your communications parameters and data.

How complicated are you looking at for your communications? I did a project a short time ago that involved sending/receiving ASCII strings for remote control. Are you trying to do something similar?


Pi

Yes I am trying to be able to set the set points of this pump, control regeneration, start/stop. Pretty much most if not all of the pumps function. Where the PLC is mounted we are limited in width and already have a full PLC rack. I was thinking of getting a S7-1200 CPU and serial card (distance will be an issue) and mounting tha S7-1200 next to the pump and from the S7-1200 to the S7-300 over Etherner. Sometimes the cabinet where the S7-300 PLC is can be very far from the pump and RS232 has limitations.

Do you require an additional CPU at this pump? If your S7-300 is already Ethernet capable, it may be easier to use a Remote I/O(ET200 style?) with a Profinet interface and the serial card instead of a full PLC. I'm not sure on the cost of a S7-1200 so I may be out in left-field here. The choice is yours. Make sure you have a good twisted-pair cable with a shield for the serial link. Noise will cause havoc on that line otherwise.

The communications you are wanting to accomplish should be doable. You will need to setup the pump commands and have the variable data be added to the command string. Siemens adds two bytes to the beginning of every string variable so keep an eye on what data is being sent. You will also need to check if you need to send carriage-returns or line-feeds with the commands. Those will need to be accounted for.

I can post some SCL code examples if you need some.


Pi

Code examples would be great.

The attached file is a quick and dirty SCL program I wrote for a test module we had in the shop not long ago. All it did was send two short ASCII command strings and received one. By manipulating the command string, you can send any number of commands you wish. The received data can also be pointed to a location as well.

You will need to make sure to pick up FB2 and FB3 (Receive and Send FBs) from Siemens for their communications modules when you write your own program. They have the download somewhere on their support site.

Hope this helps.


Pi

I am still looking to do this with a siemens and AB plc.

I did it with a Weintek HMI (KEP brand). Used macros. Must be RS232. 2400 baud if I remember correctly.
Can't use Ethernet port. That has protocol for CTI's controller only.
It was difficult. CTI manual isn't accurate with how to generate checksums.
I wrote a checksum generator in QB64. With this, I was able to see what the checksum character was for various commands. Made macros shorter and easier to write.

Simple commands are 4 characters. Start character, 2 character command, single character checksum.
Turn on: "$A1'".
Turn off: "$A0c"
Status (is it on or off?): "$A?2"
Tested using a Dell, XP Pro, Hyperterminal.

CTI Manual. Go to appendix B.

I can post files if you want. QB64 program, CTI command list with checksums.

Any programs, listings would be great.

Sorry I missed this. Hope it's not too late. Try this for QB64.
It generates commands that you can type in Hyperterminal.
If I remember, one or 2 commands didn't work. Wrong checksum. Mismatch with my Onboard software, or issue with this program.
Attached list has working commands.