Creating a multi-step temperature program

[Dr Jon Atkinson]

Hello

I recently obtained the PID control Toolkit from National Instruments which
should allow me to control the temperature of a furnace from the computer.
The toolkit works by comparing the value of a calculated setpoint with the
measured temperature and adjusting the output (in this case a voltage) to
ensure the actual temperature matches the setpoint.

I have devised a vi which calculates a moving setpoint (the user inputs the
start and end temperatures, and the rate at which it increases) - this was
fairly easy (I just used digital controls for each parameter and calculated
the increase in temperature with time). I now would like to be able to
create several steps in my temperature program (e.g. I may want to heat upto
200d
eg, hold for 10 mins, then heat up to 250 deg, hold for 20 mins, cool
down to 100 degs etc etc). The number of steps has to be totally
user-definable and could vary from 2 or 3 to over 50.

Would anyone have any idea how I could do this? The vi will need to execute
each step in turn, calculating the setpoint all the time. I tried creating a
multi dimensional array, each line containing a step of the program, but I
do not know how to extract the parameters from each line in turn. I am now
convinced that I was going totally down the wrong path and have now got
really stuck!

help please!! 🙂

Dr Jon Atkinson
University of Birmingham

[PdB]

Funny, I created a similar multi-setpoint program in the past (in LabWindows) and I will use it in my next project.
Just take two arrays. The first contains the times, the second the setpoint-value at that time.
Let the vi interpolate the setpoint from the time-array and the setpoint-value array (you already did that). When the time is reached, just add 1 to both indexes and enter the next interpolation-part.
It's not that difficult, Patrick de Boevere.

[IanW]

If you need an easy way to generate the profile there's an example program on the NI website dynocode.zip. Part of this allows you to generate a speed profile using the mouse, you may be able to modify this for your temperature application.

[IanW]

I had problems trying to find the Dynamometer Application Program file again, here's a link
Dynocode.zip

[IBI]

Dr Jon Atkinson, i have the same problem like you but i never got far. I am a newbie with Labview, and i work with the version 6.0.

Could you send me your vi with definable setpionts, (in a simple form without private or corporation information in your vi).

Thank you very much

[v-koot]

does anybody has a working example of this vi ?

kind regards vincent

[lmtis]

This is a rudimentary example.  Just add another control and array and you can input 2 variables (i.e. Temp and interval)