Read input then compare and turn on LED

[Mikea01]

Hi,

I have very little experience at writing in LabVIEW and am stuck on some basics. I was watching this video tutorial http://www.ni.com/white-paper/5370/en/ on building an analog input and all worked well. I was using a USB-6229 BNC and had a very slow varying voltage (0 to 5V) applied to Ai0.

I then wanted to to compare the varying input to a 2.5V level and then turn on a LED connected in series with a resistor to the digital output P0.0 if the input went above 2.5V and turn it off below 2.5V. It is this bit that I am stuck on. Can you help please? Once I've done a few of these exercises and find my way around, then I'll be on my way. It's just an initial bit of help needed. We've all got to start somewhere.

Thanks

[MaveenD]

Hi Mike,

Can you attach your code or take a snap ?

so that we can have a good idea were you went wrong?

[Mikea01]

Hi,

I've attached an image of the block diagram. There isn't much added from the original NI example because I really didn't know where to begin.

Thanks

[GerdW]

Hi Mike,

don't read a waveform from DAQmxRead, instead set it to "1Chan 1Sample". Then you receive a scalar value to perform your comparison on!

[Mikea01]

Hi GerdW,

thanks for your reply, but I dont really understand. As I said, my knowledge is very limited to non existent. I've got an analog input which feeds into a 'greater than or equal to' function along with a 2.5V set point. I just want to toggle a LED on p0.0 when the threshold is crossed. Any chance you could just show me this in the block diagram please? I will then undersatnd what to do and move on from there. It must be one of the simplest things to do if you know where to start.

Thanks

Mike