Temperature Control

[eFisher0409]

Hi All,

I want to start by saying thanks to everyone who helped with my motor control and speed control program, I took sometime sat down and it works flawlessly. I added in my thermocouples to tell me temperature and they work perfect, however I came up with the idea now to reach a max temperature of 600 degrees then turn off my heat source until it drops below 400 degrees then start it up again, I had an idea of using a PID but I feel there has to be a simpler and easier way. Thanks in advance for you help.

 

[sgull]

Hi

Just use the compare function., compare the temperature to the min and max values.

It the temperature is below the min value set the heater output coil.

if the temperature is above the max value reset the heater output coil

Regards

Denis

 

[Ausman]

sgull is correct, but I would also add that in a lot of cases you have to build in a bit of hysterisis/deadband/whateveryoucallitcolloquially .

The reason is that if you are working with inputs that can vary the reading slightly around an average, your output(s) will chatter which in some instances is very damaging to components.

I was a bit confused about what you want to do as the temp setting seemed odd.  My suggestion is that when you need to do something like this, a little diagram of what you want your temperature map to be is extremely helpful.  You make the Y your temperature, with X the time, and along the X you can then note how you can achieve what is needed.

cheers, Aus

[Flex727]

1 hour ago, Ausman said:

but I would also add that in a lot of cases you have to build in a bit of hysterisis/deadband/whateveryoucallitcolloquially

He's doing that - the deadband is between 400 & 600 degrees. sgull was suggesting a basic thermostat, which will work perfectly for eFisher0409's application.

[Ausman]

Ahh yes...I'm stuck in keeping it around 400 after it's been put up to 600 initially.  That's why I said I was a bit confused about what was wanted.

cheers, Aus

[Joe Tauser]

You're looking for a deadband control, which can also be done this way in addition to sgull's suggestion-

 

You can put MIs in place of the #400 and #600 which will allow you to adjust your control from screen variables.

If you're feeling brave post your program.  I'm curious to see how you've progressed.

Joe T.

 

[Flex727]

This is why Joe is the programmer's programmer. We all strive for the elegant solution.

[sgull]

Hi Joe

Never thought of doing it that way.

Much nicer than set and reset and you never have to worry about power up state.

regards

Denis