Setting up a Temperature warm up routine

[TMcDaniel]

I am trying to set up a routine to warm up some heaters at one temp for a period of time then when the time has elapsed turn the heaters up to another temp.

My temps are being set from the HMI to N7 and the output is to GRT and another N7 which is the temp reading from the thermocouple.

The process is a blow molder that on start up needs a warm up period of 30 min at 120c and then turned up to operating temps from 160c-220c. My goal is for the operator to press a warm up button on the HMI and it go through the process. (Yes i am trying to engineer out STUPID)

I have a understand the timers i just dont know how to get the button press to set the temps to what i want.

 

[Tom Jenkins]

You appear to be using Allen Bradley. Have a MOV function put the HMI preset into a register. Use a timer, as you indicate. Have the timer done bit activate a move (MOV) function to put a new preset in that register.

 

[TMcDaniel]

I will try that. Thank you

 

[parky]

Although not AB it should translate, caveats: Assumption that if above pre-start temperature then ignore the pre-start.
You could just use the not contact of the pre-start latch to move the normal set point into the working set point.
It assumes you wait until it is up to pre-start temperature before running the pre-start timer (Note: for testing only set to 30 seconds).

 

[Aabeck]

I work on hot presses where that is called "Ramping" the temperature. They also ramp the ram hydraulic pressure each step.

What I do is take the old temperature, the new temperature and the ramp minutes, calculate how many seconds per 1° step. Run a timer with the seconds per step moved to its .Pre and every .DN add 1 to the temperature setpoint until it is at the new temperature, then time how ong that step is.

One push of a button will start the ramp portion, or if running a cycle as I do on these it ramps up, times the step, then ramps up tp the next step. Repeat until the cycle is done.

 

[TMcDaniel]

Thank you for all the replys. I tried the MOV function and when I download the program and try to run the sequence it gives me a fault "Math overflow trap". Is this happening because I have the MOV instruction setting a value for an N:7 and also the HMI setting a Value for the same N:7 or is there something else i should be looking at?

 

[parky]

Post some of your code, you must be doing some maths calculation to get an overflow, moving a valid value into a variable should not cause an error unless it is outside of the limits.
For example, are you trying to move a real into an integer or vice versa.
Also do not move a value into the same register for the HMI set point, use the start up to move the pre-heat into a register, then when pre-heat time up move the HMI set point into that register.
For example:
N7:0 is pre- heat set point
N7:1 is HMI Run Set point
N7:2 is the target set point for control
During Pre-heat move N7:0 into N7:2
When Pre-heat done move N7:1 into N7:2
Bearing in mind you are using N7 so will be an integer not a floating point number you will have to use F8 for floating point values.

 

[TMcDaniel]

Here is the Move instruction

 

[TMcDaniel]

here is my temperature control.

 

[TMcDaniel]

Ok... problem solved found that I had N7:11 in two different places with 2 different max input. N7:11 was suposed to be my VFD speed control N7:12 is my temp control. I guess i should double check before I start asking for help.

Thanks for the help.

 

[parky]

No problem