topic Re: LED blinking in while loop in LabVIEW

LED blinking in while loop

jon_mcbee — Tue, 30 Oct 2007 15:14:31 GMT

Hello

My application involves reading data off of a serial port at 26Hz. I am parsing this data in real time and writing statistics to file. I want to have an LED blink each time a file is written (I have a files being written in the following intervals: 1sec, 3sec, 15sec, 60sec, 10min). My problem is that the LED only stays illuminated for the single iteration, which is dictated by the speed I am reading from the serial port. Is there a clever way to have the LED flash for a standard .5 sec without creating timing issues?

Cheers!

Re: LED blinking in while loop

Steve.Briggs — Tue, 30 Oct 2007 15:20:11 GMT

In order to make an LED "blink" you can create a property node and select blinking.

Do you have the files written only 5 times at 1sec, 3sec, 15sec, 60sec, 10min, resulting in 5 files. Or do you have files written every 1sec, 3sec, 15sec, 60sec, 10min?

Re: LED blinking in while loop

jon_mcbee — Tue, 30 Oct 2007 15:25:20 GMT

Thank you for the reply, I create a new set of five files at midnight and append to them throughout the day at the given interval. As I understand it the property node causes the LED to blink at a set interval. I am looking to have the LED blink at the predetermined interval (1sec, 3sec, 15sec...) and stay illuminated for 0.5sec each time it blinks. I have the triggering for the blinking worked out so that it blinks when I want it to, the problem is that it is in a while loop that is executing very quickly and so the LED doesnt stay illuminated for very long when it does blink. I hope that this helps.

Cheers!

Re: LED blinking in while loop

Steve.Briggs — Tue, 30 Oct 2007 15:33:00 GMT

Do you have other activity inside of this while loop? If not you can just put a Wait command that will keep the LED illuminated until the wait is over and the loop moves on to the next iteration.

Attaching your code will help as well

Message Edited by Steve.Briggs on 10-30-2007 11:33 AM

Re: LED blinking in while loop

jon_mcbee — Tue, 30 Oct 2007 15:47:52 GMT

The while loop is primarly used to to read the serial port and write the data to file. The problem with using a wait millisecond command is that it will throw off the reading from the serial port, the most I can wait is 38 milliseconds otherwise I will miss data at the port. I will see about getting my code up, unfortunately I will be out of the office for most of today. Thank you very much for the help!

Cheers!

Re: LED blinking in while loop

Steve.Briggs — Tue, 30 Oct 2007 16:51:19 GMT

Somehow incorporating the wait with the timing intervals for your read could do the trick. For instance, you read at intervals no less than 1 second, so instead read at an interval of 0.5 second, and have the wait for 0.5 seconds. You'll get both the 0.5 second illumination of the LED and a read that performs 0.5 seconds after, giving you 1 second. Same thing goes for the other intervals you wish to read at.

Re: LED blinking in while loop

LabViewGuruWannabe — Tue, 30 Oct 2007 19:44:59 GMT

Perhaps a simple timer would work. Either the Elapsed Time vi or the Get Date/Time in Seconds. Use a boolean that gets set at the time you read the data, and resets the timer. After the 0.5 seconds of elapsed time, change the indicator. That shouldn't use a while loop or any delay, so it shouldn't affect your reading or writing of the data. I just posted a simple example here: http://forums.ni.com/ni/board/message?board.id=170&message.id=281242&jump=true#M281242

Hope it helps.

B-)

LED blinking from counter input

immi — Sun, 22 Feb 2009 07:50:27 GMT

hi,

I am looking for a similar solution to my problem and hope some smart guy here could help me for this. I am reading sync pulses from a laser (1 to 20 Hz) through one of the input counters of my DAQ PCI 6221.I am able to read the number of pulses at input counter however, I would like to let a LED blink on each edge detected at input counter. In other words, I would like a boolean output for each detected pulse.

thanks

immi

Re: LED blinking from counter input

VENKATESH.J — Sun, 22 Feb 2009 08:03:48 GMT

Hi immi,

Check out this vi. This Vi make the Led blink, when it detects a Rising/Falling Edge in the signal.

Rgds,

Venky

Re: LED blinking from counter input

immi — Sun, 22 Feb 2009 08:33:22 GMT

Hi Venky,

Thanks for prompt reply. Sorry I forgot to mention that I am using Labview V8.0 and the Vi is not opening with it.

regards

immi

Re: LED blinking from counter input

VENKATESH.J — Sun, 22 Feb 2009 09:23:29 GMT

Hi Immi,

Check out this 8.0 Vi.

Rgds,

Venky

Re: LED blinking in while loop

immi — Sun, 22 Feb 2009 10:26:19 GMT

Hi Venky,

Thanks..I see only one ex-or gate with 2 switches and a LED in the vi. I hope nothing is missing in it.

rgds

imran

Re: LED blinking in while loop

VENKATESH.J — Sun, 22 Feb 2009 10:52:04 GMT

Hi Imran,

Yeah it is not missing anything.

It detects the transition ,whenever the Signal boolean changes its value from true to false or false to true.

Note: for help check context help (Ctrl+H) of the Edge detection.vi

Let me know if it meets ur requirement or not.

Rgds,

Venky

Re: LED blinking in while loop

immi — Sun, 22 Feb 2009 12:12:14 GMT

Dear Venky,

To eleobrate my problem, i am attaching an image of the part of the vi. As you can see the information I am getting from the hardware through the DAQmx is a DBL precision number and I dont see any direct boolean signal readout from the counter. Hope this will give you a better view of the problem. I need to be able to read the logic level of the counter first in order to get the edge detection work.

Rgrds

imran

Re: LED blinking in while loop

A_Person — Mon, 23 Feb 2009 23:27:28 GMT

Hi Imran:

Is there any reason why you cannot use a digital input rather than a counter? This would give you a boolean value that you could use with the code from Venky. If you do have to use a counter, can you provide some more background on what your application is doing?

Message Edited by A Person on 02-23-2009 05:27 PM

Re: LED blinking in while loop

immi — Sun, 01 Mar 2009 20:24:15 GMT

Hi Alex,

I am developing a laser ablation system for which i need a simple control of a laser equipment for generating specific number of pulses and stepping a stepper motor after each pulse (falling edge). I tried to use a digital input but apparently the DAQ digital input is not able to detect the input pulses which are (50 us) short. Counter input detects is easily and accurately but I cannot get a logic level information from counter and which is my basic problem. i read the help and the only way i can use digital input of my DAQ card is it to configure it as "detect changes" and hardware timed but in that case it i noticed it missed to detect some pulses and accuracy is compromised. Please bare with me as i am not an expert user of LabView.

regards

imran

Re: LED blinking in while loop

immi — Mon, 02 Mar 2009 05:54:05 GMT

Hi Alex,

I am developing a laser ablation system for which i need a simple control of a laser equipment for generating specific number of pulses and stepping a stepper motor after each pulse (falling edge). I tried to use a digital input but apparently the DAQ digital input is not able to detect the input pulses which are (50 us) short. Counter input detects is easily and accurately but I cannot get a logic level information from counter and which is my basic problem. i read the help and the only way i can right now use digital input of my DAQ card is it to configure the advanced clock settings to "change detection" and hardware timed but in this case it i noticed it is missing to detect some pulses and accuracy is compromised. Please bare with me as i am not an expert user of LabView.

regards

imran

Re: LED blinking in while loop

A_Person — Mon, 02 Mar 2009 22:53:07 GMT

Hi immi:

So 1 to 20 times per second, you are receiving a 50us pulse? Your digital input should be able to detect that without a problem. One thing you can do to help make sure you detect the pulses is to turn off the filtering as shown in the example. Give this example a try and see if you can detect the digital pulses. Otherwise, we can try and come up with a solution that uses a counter.