siemens S7-200 + encoder + frequency variator

[juan]

Are there already some examples available of a project to combine the next topics :

Computer control by Visual Basic user interface
Siemens PLC S7-200
Siemens micromaster frequency variator
Encoder eg OMRON
3PH motors

Thanks in advance... I'll let you know when I find more about this topic...

 

[seppoalanen]

Visual Basic

Can You use SimaticNet OPC-Server properties as DDE or ActiveX Read/Write ?
Anyhow it means OPC-Server polls selected variables for reading to VB-application and writes when VB-application writes to OPC. It could be possible in VB OPC-ActiveX control make event when OPC sends 'data has changed' who start you SUB-program who reads variables from server so VB-application can be as 'real' Windows application....

If you use some free-protocoll in PLC, your plc-application can write when data has changed and your VB-application MSComm32.ocx ActiveX control event 'inputlen' starts some SUB-program who reads it from serialport to some variable(s).
I belive free protocol is possible somehow (as fixed len message).

Micromaster

How do you like control it ? Profibus, BIO, AIO ?

Encoder eg OMRON

Absolute-, inkremental- ? for what ? Profibus ?

 

[juan]

Thanks for your interest...

The problem that we have is like this:

We have already an existing system that is working, but the problem here is that there are no schematics available, so we don't know what is in the PLC. We have the program source on the PC from the program in Visual Basic.

We have to make a system rotate by two axis, X and Z so we can do measurement. The visual basic program let us configure the rotationangle and the timespace between the rotations...
The PC is connected with the PLC through a PC/PPI cable and from there on we drive the motors to turn via a frequency variator. When the reaches the end point, the encoder alerts the PLC so that the frequency variator can stop the motor by use of a brake.

We were searching for some examples that were made like this, so we can interprete better what is happening in our system, so we can improve it, eg changing the incremental encoders to absolute encoders so we always know in what exact position we are, even after some power drop down...

Is this usefull to change the encoders? Or can we do this by some other trick?

What kind of program is in the PLC, because this one is pasword protected, grrrr...

Thanks again for your interrest...

Giel and Juan