G120 controlled by PLC s7-1200 and extra commands by runtime advanced

Hello,

I have a CU240E-2 PN that is controlled by a PLC s7-1200 trough PZD words. I would like to add an extra command, in the runtime advanced, by writing to the application function, free blocks, logic function OR1.

I have configured it to be acyclic, but will this new S7 connection mess with the PZD from PLC?

Hi, 

so I see you just also read some actual values like the actual speed directly from the drive via your HMI. 

First: Yes, it is possible to have cyclic and acyclic communication in parallel. The cyclic one will always work in a certain cycle. The acyclic one is much slower and depends always on the utilization load of the drive etc - so you cannot know how long it takes to receive new values, can be from several miliseconds to several hundred miliseconds or even longer.

Secondly: Why do you do this? I mean why are you reading the actual values acyclically from the drive when you already have a cyclic connection between PLC and drive -> you should use the cyclic data exchange (via PZD) to read out the actual values and then simply display them in your HMI. In my opinion it is absolutely not necessary to read the values additionally via acyclic communication.

RB91

Hi, 

so I see you just also read some actual values like the actual speed directly from the drive via your HMI. 

First: Yes, it is possible to have cyclic and acyclic communication in parallel. The cyclic one will always work in a certain cycle. The acyclic one is much slower and depends always on the utilization load of the drive etc - so you cannot know how long it takes to receive new values, can be from several miliseconds to several hundred miliseconds or even longer.

Secondly: Why do you do this? I mean why are you reading the actual values acyclically from the drive when you already have a cyclic connection between PLC and drive -> you should use the cyclic data exchange (via PZD) to read out the actual values and then simply display them in your HMI. In my opinion it is absolutely not necessary to read the values additionally via acyclic communication.

 Hi RB91,

Thanks for the input.

The client will use this scenario in case the PLC is dead and we wants to be able to operate the drive in emergency mode. In a very simple way, only sending the On signal and seeing the actual speed.

ok understood. 

So having cyclic and acyclic communication in parallel is no problem. 

The only thing you need to consider for your use case is how you react in the drive when the PLC will shut down - usually you will get an error on the drive when the cyclic communication stops and the drive will switch off. Then you could just restart it from your HMI. But be aware: After a fault (drive switched off) you always need a positive edge at the OFF1 command to restart -> I just mention this because of your "OR" logic. Also you need to think of how to hand over the speed setpoint to the drive then (if it comes from the PLC you need another source then, if it is a fixed setpoint then no problem).

Another idea would be to use 2 Command Data Sets. First one for PLC communication (setpoint and On signal coming from the PZD) and the second one you can write your commands from the HMI. The switchover between the data sets could be done via Digital inputs or maybe also via a acyclic write command from the HMI. 

RB91

ok understood. 

So having cyclic and acyclic communication in parallel is no problem. 

The only thing you need to consider for your use case is how you react in the drive when the PLC will shut down - usually you will get an error on the drive when the cyclic communication stops and the drive will switch off. Then you could just restart it from your HMI. But be aware: After a fault (drive switched off) you always need a positive edge at the OFF1 command to restart -> I just mention this because of your "OR" logic. Also you need to think of how to hand over the speed setpoint to the drive then (if it comes from the PLC you need another source then, if it is a fixed setpoint then no problem).

Another idea would be to use 2 Command Data Sets. First one for PLC communication (setpoint and On signal coming from the PZD) and the second one you can write your commands from the HMI. The switchover between the data sets could be done via Digital inputs or maybe also via a acyclic write command from the HMI. 

Thanks.

At the moment I have two CDS, the [0] is with a fixed setpoint and the [1] is defined by the PLC. One doubt that came to my mind is if I should define the S7 connection, to the runtime advanced, to be cyclic, so that in case of loss of communication the drive goes in to stop mode. Can we have two cyclic communications with a drive?

So, I have tested and I can see the speed value directlly from the drive. So I know that the runtime is receiving data from the drive.

I cannot send a ON command to the drive. I tried to write 1 to D20050.DBD0 (OR1 Unsigned double word), but it did not work and even tried to write 100 to DB2900.DB0, but did not work. The drive is configured for profinet command. I think I have to link the input 0 from OR1 to some parameter, but don't not witch one, since the PZD words come from the PLC.

I thougth the first input of the OR function is assigned to the PZD (Control word 1 - the bit that is usually directly assigned to OFF1 command). 

And the second OR input you write directly from the HMI 0 or 1. I think to set a BiCo to "1" you need to write the value "1111 1111 1111 1111" acyclically -> not a 100% sure - please check it in the function manual for communication under acyclic communication. 

And the output of the OR function will be connected to OFF1 (p840). 

If you work with data sets you can also skip the OR function and keep the connection of the PZD to p840[0]. And for p840[1] you can try to write it acyclically - don't know if this works. Be aware to always have a 0-> 1 positive edge at OFF1.

Please check out this application example for HMI direct access to SINAMICS:

https://support.industry.siemens.com/cs/de/en/view/109481157

There it is shown how to control the drive from the HMI directly.

Manage to solve the problem. To send a ON command to the input 0 from OR1 I had to write 65536 to the %DB20050.DBD0.

Is odd that we do not see the inputs of the OR gate change, but only the output.

Thanks,

Bruno

RB91

I thougth the first input of the OR function is assigned to the PZD (Control word 1 - the bit that is usually directly assigned to OFF1 command). 

And the second OR input you write directly from the HMI 0 or 1. I think to set a BiCo to "1" you need to write the value "1111 1111 1111 1111" acyclically -> not a 100% sure - please check it in the function manual for communication under acyclic communication. 

And the output of the OR function will be connected to OFF1 (p840). 

If you work with data sets you can also skip the OR function and keep the connection of the PZD to p840[0]. And for p840[1] you can try to write it acyclically - don't know if this works. Be aware to always have a 0-> 1 positive edge at OFF1.

Please check out this application example for HMI direct access to SINAMICS:

https://support.industry.siemens.com/cs/de/en/view/109481157

There it is shown how to control the drive from the HMI directly.

 Hi Robert,

Regarding p0840 its index updates only with CDS and not with data sets.