Downcounter

Hi

I'm working on a project with a siemens 200 plc and i would like to have some help to do some kind of downcounter.

This is how it should work:

The operatator sets a starting time on a op7 display (date, hour, minute) and when the time is reached the machine will start.
When a starting time is set i would like do have a downcouter on the display that shows how many days/hours/minutes that is left until the machine will start.

Can anyone help me?

I would have a compare function subtract the current time from the start time and display the result.

russrmartin said:

I would have a compare function subtract the current time from the start time and display the result.

Click to expand...

Hi russrmartin and thanks for your reply.

Could you please give me some more details about how this works on a s7-200 plc

Unfamiliar with S7

As the title says, I am very unfamiliar with S7, but, in theory, what you would happen is this. The operator enters their start time on some sort of interface. This interface will write to registers in the PLC. Almost every PLC I am familiar with has registers devoted to the current date and time. Take the time entered by the operators register and subtract the current time, which will be stored in a 3rd set of registers. The HMI then displays the value in these registers. You may have to do this one subtract block for hours, one for minutes, etc. When your current time is = to the start time they entered, your time remaining will show zero and you can turn off the subtraction blocks. There are other ways I am certain, and some may be easier, this is just one way. Good luck.

Russ