S7-1200 Prog.advice

[tulip]

Hi .I make a project .When process arrive X celcius ( this value is entered on HMI ) then Y minute wait.(this value is entered on HMI also).When the temperature reaches the value entered on the screen a flag will be set and the waiting time will start running. When the time is up, other steps will be taken.Is there any standart block in TIA will also work like a stopwatch? If not, do you have a solution suggestion? Thanks in advance..

 

[drbitboy]

Yes the TON instruction. Also the TOF, but the feed logic would be different.

The trick is to maintain the input rung to the TON instruction as True even if the evaluation of the [Temperature Reached X] condition changes from True to False. Use [NO ton_object.IN] to do that (Start/Stop, seal-in]. Or use a pulse timer TP if is is only the rising edge of the [Temperature Reached X] event that matters.

See this link.

 

[parky]

How are you controlling the temperature (if at all), the way you explain it is a little vague, for example do you need to hold it at the set point temperature or is that already controlled, do you need to keep it at that temperature during the wait time ?.
Examples: if you are using an HMI for input of time then I suggest you use a variable incremented off a timing pulse.
attached, is a pic of something you could do, note this is not in S7 but easily converted.
The attached has assumed you have some bit that starts the heating cycle & this is controlled in some way i.e. PID or perhaps just pulses the heater to keep it up to temperature or it just achieves temperature then holds until next step.
So, when the heating is running it compares the current temperature with the setpoint on the HMI, when it reaches (or goes above) the setpoint it sets a bit that starts the hold time, this is in this case in seconds i.e. adds one second to a variable, compares this with the HMI hold time setpoint, when it is equal or above then it sets a bit & resets the other bits & zeros the time variable, then you use this bit (hold time complete) to continue doing what ever is the next step, note: you could use a timer (if IEC timer then depending on your HMI if it will accept IEC time as a setpoint no problem) but in this case I'm using the setpoint in seconds to keep it simple.