Split range Function RSLogix 500

[Jlopez832]

Hello everyone,

I am currently working on my senior capstone project, I'm having trouble trying to figure out how to set up a split range control for my project. I'm trying to control temperature using the split range between a heating element and cooling fan/heat exchanger combox and a thermocouple as my measured variable. My current set up is a Micrologix 1400 which uses RSLogix 500, and after searching the web and reading the manual I'm not finding any luck or yet something I can fully understand.

 

[parky]

The guys or girls (got to be pc) really need more information i.e. is this just digital or analogue controls to heat/cool, has the unit got PID controllers on it etc. It would be easy to say turn on heat if below temperature or cool if over temperature, however bang bang control might put a lot of pressure on the unit & what sort of dead band can be tolerated, there are so many scenarios.

 

[Jlopez832]

The unit has a PID controller and our deadband is between 49-51%. What im trying to achieve is that from 0-49% controller ouput it will be heating then it would have a deadband, and then from 51-100% of the controller ouput it would be for cooling. The heating and cooling will be controlled via analog signals. The heating element is controlled throughout a solid state power controller that uses a 4-20mA signal and the cooling fan uses a 12V PWM that accepts a 0-5V signal. Bascially I'm breaking my head to see how i can split the controller output on a RSLogix 500 PID function. It is using a analog signal from a thermocouple as our sensor or measure variable.

 

[danw]

Here's some ideas in graphics:

 

[Horhes]

Honestly, the last answer is just perfect, the only thing that would be great if there was a base database with similar information!

 

[rupej]

The unit has a PID controller and our deadband is between 49-51%. What im trying to achieve is that from 0-49% controller ouput it will be heating then it would have a deadband, and then from 51-100% of the controller ouput it would be for cooling. The heating and cooling will be controlled via analog signals. The heating element is controlled throughout a solid state power controller that uses a 4-20mA signal and the cooling fan uses a 12V PWM that accepts a 0-5V signal. Bascially I'm breaking my head to see how i can split the controller output on a RSLogix 500 PID function. It is using a analog signal from a thermocouple as our sensor or measure variable.

Just use the SCP function to scale the output of the PID to the output for the two control elements. Then trim that value to make sure they won't turn on when outside of their range.