Enquire about acquiring analog signal of wheatstone bridge from DAQ device to labview to read certain voltage values

[Leni]

DAQ assistant function is being used to acquire analog signal from NI USB-6009. So, to read a voltage values out i used a numeric indicator icon. Is this the correct method?

[MikeS81]

Hi Leni,

the correct method for what? What do you want to do? If you want to see the value and it works for you, then it is correct.

Mike

[Hillman]

Hi Leni.

Firstly, as MikeS81 said - we need to know more about your setup to answer your question.

However, for your reference.. here are some useful links on wheatstone bridges and reading/converting values.

Link - measurements with strain gauge (dynamic resistance)

link - converting voltage to x (in this case strain, could be temperature or whatever).

forum - link to a forum post about strain again.

Please post back soon so we can discuss things further,

Regards

[Leni]

Do we need to create a while loop within that DAQ assistant and numeric indicator?

[Hillman]

Hi Leni,

If you want to continuly update the indicator - then yes.

Regards

[Leni]

btw do u have any reference for the if else statement regarding true or false condition?

[Leni]

DAQ assistant is used to acquire analog signal from NI USB-6009 to read certain voltage out values from our wheatstone bridge.

We also generate signal from digital output of NI USB 6009 to move our motor to forward/reverse using our LM293 circuit. This circuit is also called h-bridge. Using an array constant to give toggle switch funtions to 'High' or 'Low'. Pin 1, 2 and 7 are connected to P0.0, P0.1 and P0.2 respectively to generate that signalt to DAQ assistant.

When Pin 1 and 2 are switch to 'High', Pin 7 to 'Low', the motor will move forward. Pin 1 and 7 are switch to 'High', Pin 2 to 'Low', the motor will turn reverse and etc. Pin 1 act as enable.

So, between wheatstone bridge and h-bridge, what best method can be used to implement the motor to move forward/reverse. Other than using toggle switch for h-bridge, is there other method to do it? Can we create a case structure for our if else statement to automatically toggle the switches so that we can control our wheatstone bridge externally by using the potentiometer?

[Hillman]

Hi Leni,

You find lots of very good information about controlling motors from LabVIEW with NI motion control hardware under this link:
http://www.ni.com/motion/

However, depending on your application this could be over complicated.

It sounds like you've got a good circuit for controlling the motor - a hbrdige design is classic and works very well. When you say toggle switches, are you talking about switches on your front panel?

If not, then you can connect your BJTs or MOSFETs gates to the output pins of the USB-6009 to control their states.

So, just to check I understand, you want to controll your motor depending on Analog input (from potentiometer?) to your vi? This would be possible. Use a DAQmx AI task (see examples in help>>example finder...) then with some code you could either output forward or reverse commands.

Regards

[Leni]

Yes, i was talking about the switches in the front panel. These switches are for our h-bridge. An array constant is to supply the toggle switch. What is the main function of an array constant? Am i using the correct method?

Our potentiometer is to control the motor to turn forward and reverse. That potentiometer is from a wheatstone bridge circuit which we measure voltage out using AI0 of our DAQ device.

So, between these wheatstone and h-bridge circuits, we want to control the motor to forward and reverse using an if else statement. When the potentiomenter turns, gives the value of voltage out to let say 5V. What i want to achieve is if 5V are less than 10V, it will return true condition and if its greater than10V return false condition. By using potentiometer, we can control the h-bridge to either left/right.

[Leni]

You were saying we can use DAQmx AI task. But we using DAQ assistant instead. Is it better to use that DAQmx function?