Reading from the Serial Port

[PSUstudent]

Hello I am looking at reading a voltage from an external source, and using that voltage to trigger an event if it is above some value or not. Is this possible to do with the serial port.

I know some of the other posts on serial port things involve a stream coming into the serial port, but we don't have a stream. If the serial port is not possible to use, then might you have a suggestion of what I could use. Our options are USB, serial, PS/2, ethernet port, and firewire port. We are using LabVIEW 8.0

Thanks

[Mark Yedinak]

This can't be answered without more information about what you will be using to actually read the voltage. If you are asking if you can use a serial port itself to read voltages the answer is no. If you are asking if you can use the serial port to get the reading from some other piece of equipment then the answer is it depends.

[BrokenArrow]

QUOTE (PSUstudent @ Mar 30 2009, 04:23 PM)

Hello I am looking at reading a voltage from an external source, and using that voltage to trigger an event if it is above some value or not. Is this possible to do with the serial port.

I know some of the other posts on serial port things involve a stream coming into the serial port, but we don't have a stream. If the serial port is not possible to use, then might you have a suggestion of what I could use. Our options are USB, serial, PS/2, ethernet port, and firewire port. We are using LabVIEW 8.0

Thanks

You need an A/D converter between your computer's port and the voltage source. Do you have that?

You said you want to monitor the voltage and trigger upon a certain value. If you have a "voltage", then you have a "stream", so I don't understand when you say "we don't have a stream". You don't have a stream because you haven't built a pipe (interface cable) and selected a pump (hardware) to get the water from the stream to your computer.

[Warren]

I have a question that is similar to what PSUstudent was asking - (Im not sure if I should have made a new topic for this.) Anyways, I am conducting an experiment that records/ displays an input signal from a lock-in amplifier. - this process is already done. However I want to be able to select the data that I am recording remotely - from the other side of the room. I was thinking that I could build a toggle switch near my experiment bench that when turned-on would activate the recording process. - Ironically, This has turned out to be more of a problem to understand/ build than the actual experiment set-up.

My question is how can I take a constant voltage and trun it into somthing meaningful for labview?

I have already taken a look at the "basic serial write and read" example, but still feel like thats not exactly what Im looking for.

Any help would be appreactiated, or an alternative soultion.

Thanks - Warren

[Tim_S]

QUOTE (Warren @ May 20 2009, 03:18 PM)

My question is how can I take a constant voltage and trun it into somthing meaningful for labview?

Typically I would have a digital input in the form of a PCI card, remote I/O, etc., and I would wire the switch to that. Then it would be a matter of communicating to the card/bus and getting the state of the input. This would be a preferred method. You can get a USB based solution for about 100 USD.

You can use a parallel port as a digital input device. A little web search should provide you with the information you need. There's risks to doing this such as blowing out your parallel port or (if you're really unlucky) your motherboard. This does assume your PC has a parallel port.

Tim

[Warren]

Thanks for the reply. I'm still a little unsure how I would go about doing that - I had a good long google search, but I couldn't really turn anything useful up yet. (I probably don't know enough to ask the right questions) but I think I might have figured out a way to circumvent the ugliness and still accomplish what I need to. Ill let you know if it works out.

- Warren.