pid temp. control

[zdkred6]

hi all,

was wondering if anyone out there was able to help me with this.

firstly just a small bit of back ground info about me. i'm a student with a little labview experience, i'm running labview 2009 and using a NI USB-6008 DAQ.

i need to write a labview program that controls air temperature using PID. i will have an anolog input (v) for the temperature read and 2 digital outputs, 1 for the DC fan and 1 for the heating element.

i have done a small bit on this already. using the DAQ assist i can get the AI and in put it to a PID sub VI. when i try to conect the output from the PID vi. to the DAQ assist for the DO's i am unable to. also i'm not sure if i can switch the 2 DO seperatly or do they have to come on together? what i mean is will i be able to switch on the heating element and then pulse on and off the fan as the temperature rises to the set point? i hope this makes sence.

if anyone can please help me with this it would be greatly appreciated.

[viSci]

PID is based on Proportional control so it expects your output to work with a 0-100% range, in your case it would have to be PWM and you will need to setup a timer to

control the pulse width. Also remember to scale all of your inputs and outputs to % full scale.

[zdkred6]

PID is based on Proportional control so it expects your output to work with a 0-100% range, in your case it would have to be PWM and you will need to setup a timer to

control the pulse width. Also remember to scale all of your inputs and outputs to % full scale.

hi sachsm,

thanks for the post. i understand what you are saying but to be honest don't know how to do it in labview. can you sugest somewhere were i can see an example of this. i have tried the NI website but cant find anything on PWM. also i can find lots of examples for AI / AO for the 6008/9 but none for AI / DO. do you or anyone else no where i can find some examples on this please.