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usb 6008 digital i/o

Hi all I am currently building a project for college.I am building a pid control loop of the temperature of a container of water.I have a watlow 96 which reads the temperature from a theromocouple and then outputs a voltage 0-5 variable depending on the process temp.I then take in this informationa and process it through a pid loop.Depending on the output of the pid i want my usb 6008 to switch on and off a solidstate relay.I have a little relay board which has 8 relays on it.These are switched onn and off by 8 transistors so i am using labview to switch onn and off the transistors.

 

My problem is this i am unsure of what how to setup the max tasks to read and write the digital i/o as they are either on or off and i dont know which digital read max task to use  with all the u8,u16 etc selections available.also when using the max tasks should i be making these tasks local or gobal tasks?

 

I have uploaded the vi so far and also a drawing of what i am hoping to connect to the system electrically.could someone have a quick look at it and tell me where i am going wrong or help me get the correct digital task

 

Thanks

 

Dec

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Message 1 of 6
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Hi, I am not sure, I think your wiring is incorrect.

Check User Manual USB-6008 http://digital.ni.com/manuals.nsf/websearch/7781F8E689519ED786257411006FB09F

Section "Digital I/O Circuitry"

 

 

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Message 2 of 6
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Doesn't the 96 have its own PID control loop built into it with an output to control a heating or cooling device? No need for LabVIEW or a DAQ.

Or does the project require the use of LabVIEW, maybe I misunderstood.

 

-AK2DM

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"It’s the questions that drive us.”
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Message 3 of 6
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Yes it has its own pid control but my project requires that i use labview to preform the pid calculations
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Message 4 of 6
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You really should have continued these questions in the original thread.
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I can reconfigure the wiring so that the inputs switches a loop from the output of the usb unit through a relay and back  to the ground terminal of the usb unit but i still am unsure of how to set up a correct max vi to read a change from on to off.However i do need to get a 5 volt output also from the unit.Do i need to get a "pull up relay" to increase the output current of the usb unit and i also need the correct vi to preform this also

 

Thanks

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