Duty Cycle - Calculations

Hello,
I have spent the most of the day trying to figure out why my duty cycle calculations were not going any faster then .1 sec.
I am aquire data from 13 accelerometers at a frequency of 20000 Hz. When I put this through the Express VI to calculate the duty cycle, the time step always goes to .1 sec.
My question really is it possible to make this faster? The duty cycle of my accels are around 10ms.
I tried to dive into the express vi's front panels, but that didn't seem to have any good answer.
Thanks,
Royce

I think that you mis-understood what I was getting at. I get excellent readings in terms of the duty cycle output. The accels duty cycle ranges from around .25 -> .75 in my case. I even setup a nice little config block to get everything to around .5 to adujust easily to gravity readout for all 13. The problem that I am having is that the duty cycle conversion doesn't seem to read out all values of the input. The duty cycle will readout only 1 sample every .1 secs. That readout I believe should really be less then .01 secs depending on the resistor values that I have set up for my accels etc. What is even more interesting is that with the dynamic data readout, if I were to probe the data. Since I am reading at 20000 Hz, it is telling me that my dt should be .00005 secs. Which was fine for sampling of my input duty cycle wave, but afterwards that dt value should be scaled down to the actual frequncy. Now, if the program was written to take an average of duty cycles over .1 secs to fix the output period to a standard amount instead of having all sorts of strange step sizes since each reading (accel) generally has a different output frequncy the program forces that conversion to .1 sec period then fine or that is just takes a sample of 10, I guess I will have to deal. But, I did have the option to have a lot higher sampling rate for my accels, and if the .vi forces everything to .1 sec period for duty cycle output or if it takes an average of 10 readings and then rounds to the nearest sig digits this should be documented in the .vi for the duty cycle so that it is clear. If I am way off base and I shoudln't be getting a reading resulting from the duty cycle every .1 secs then I guess I am really lost. But, I do understand where the duty cycle readout comes from, that part is simple enough.
Thanks!
Royce

Similar Messages

Load Collective / Duty Cycle calculation in DIAdem

This is probably quite simple to do, but as yet I have only got part way there, so I could use some help!
Basically I have some shaft torque and speed datalog files, from which I like to extract a table of number of shaft revolutions at discrete torque levels for use in CAE fatigue analysis, like this:
423 revs @ 1000 Nm
569 revs @ 1200 Nm
143 revs @ 1400 Nm
The "quantize" script gets me part way there - this can reduce the torque curve to 200 Nm steps, and it's easy enough to integrate the speed to give the cumulative number of revolutions, but now I need to count the number of revolutions at each quantized torque step, and output the results.
There must be a way to do this with all the tools available in DIAdem, but being a new user, I'm struggling to find the correct method.
Any help would be appreciated, thanks.
Solved!
Go to Solution.

Im not intending to steal this thread but I have a quesiton very similar to this...
I have some RPM and Load data in addition to Fuel Consumption data. Attached are some pictures of an example an individual from Germany has done along these same lines but I cannot seem to replicate the process.
My goal is to generate a 3D plot with Engine Speed (RPM) and Engine Torque (%) on the x and y - axis respecitively and % Fuel used on the z-axis. I've been playing around with the Compound Classification function in the ANALYSIS tab.
Can someone point me in the right direciton regarding this?
Thanks,
~Nate
The first attachment is the example from the German individual
The second attachment is my current setup
Attachments:
Germany Load Collective Example.JPG ‏296 KB
MySetup.JPG ‏202 KB

How the duty cycle is calculated by Timing and Measurement.vi

I am using the Timing and Measurement express vi(LabView8.0 is used) to measure the Duty cycle and frequency. I want to know how the same is calculated by the Timing and Measurement express vi. Please reply.

The Timing and Measurement Express VI uses \vi.lib\measure\mascope.llb\Pulse Measurements N chan.vi to do the Duty Cycle and Frequency measurements.
Help says the following about this VI:
Accepts a periodic waveform or an
array of periodic waveforms and returns the period,
pulse duration (pulse width), duty cycle (duty
factor), and pulse center of a selected pulse and period.
Refer to the Pulse and Transition Measurements VI in the labview\examples\measure\maxmpl.llb for an example of
using the Pulse Measurements VI.Maybe NI can explain the algorithm.
Hope that this helps,
Bob Young
Bob Young - Test Engineer - Lapsed Certified LabVIEW Developer
DISTek Integration, Inc. - NI Alliance Member
mailto:[email protected]

NI 5105 - Measure PWM Waveform Duty Cycle

Will the Positive Duty Cycle scalar measurement in the NI-SCOPE software calculate duty cycle correctly on a PWM (pulse-width modulated) waveform? I have a 400Hz signal that is pulse-width modulated with a 40Hz signal that I need to measure the duty cycle for. Since this is not a normal, continuous waveform (like a sine wave or square wave) I don't know if the NI-SCOPE software will correctly calculate the Duty Cycle. Has anyone tried this with success? I am looking at using the NI-5105 because it has 8 channels, but am open to using other hardware and just multiplex my signals to the digitizer.

The positive duty cycle scalar measurement should correctly calculate duty cycle on your pulse. By default, the measurement finds the base and top of your waveform using a histogram of the Y values (there will be peaks in the histogram at the base and top values). Duty cycle is calculated from the 50% level crossings between these two values. You must have at least one complete cycle and only the first cycle is measured.
If that doesn't work for you, there are a plethora of parameters you can change (except for which pulse you measure - it is always the first). For example, you can set the upper, lower, and level crossing values to specific % or voltage levels. See the documentation and examples for details.
If you need to measure the duty cycle of multiple pulses in the same pulse train, there is a LabVIEW function (Pulse Measurements.vi) which allows you to do this. It uses the same algorithms as the internal NI-SCOPE routines.
In either case, the measurement is independent of the hardware. Any NI-SCOPE device will work. If you have any other questions, let us know.
This account is no longer active. Contact ShadesOfGray for current posts and information.

Duty Cycle measurement

Hello all,
I am attempting to Measure and output duty cycle to a device. I don't have the device in my possession so I have my hardware hooked up to each other. I have NI 9472 output card hooked to a NI 9423 input card. I have found these 2 examples of how to adjust duty cycle and how to read duty cycle. They work great, but the reading of the duty cycle is oppesite of the outputing of the duty cycle. For example if I set my output duty cycle to 60% the reading is 40%. If I set my duty cycle to 30% it reads that it is 70%. I looked thru the block diagram to see if the input was looking for the resting signal to be low or hi. Being a new user it might be right in front of me. Can some one take a peak at them and tell me anything? Thank you.
Attachments:
Modify Duty Cycle while running.vi ‏31 KB
Meas%20Duty%20Cycle%20Cont%20LabVIEW%208.2[1].vi ‏31 KB

Hey greentea2,
You can try taking your waveform data and adding a replica of itself to the end of the data using the Append Waveform VI, so that you have multiple cycles of data to send into the Timing and Transition Measurements Express VI or the Transition Measurements VI for calculating the rise time. I've attached a picture that shows a simple example of this using a sine wave.
If your data does not complete a full cycle that comes back to a similar starting low point, then this example may not work for you or give you the right value. If that is the case, then please respond with a picture of what your waveform looks like, so we can determine how to manipulate it.
Hope this helps,
Attachments:
Append Replica Wave Form Data.png ‏28 KB

Calculate Square wave Duty Cycle

Hello everyone,
I'm acquiring (with USB-6212) a square wave, "100Hz" with variable duty cycle - which can be 20%, 50% or 80% - for matters of decodification; the acquisition frequency is set to 4k. Actually, I said the frequency is 100Hz, because I get a rising edge every 10ms, but the length of the high level is defined by the communication protocol and that is what I called duty cycle (even though this does not match the exact definition of this property)
Since I need to decode the information contained by the wave, it's necessary for me to be able to tell what the duty cycle is. I've acomplished this so far by taking the derivative of the signal, then calculating peaks and valleys index in the waveform and finally subtracting them, as shown below.
It works ok almost the whole opeartion, however, the acquisition is not 100% exact. Sometimes I get the signal in the picture A, that is ideal for what I intended.
Other times, the signal is like B and the derivative amplitude does not cross my threshold, even though there is a rising edge there. I could lower my threshold to 2, for instance, but then I'd get vulnerable to the signal in picture C, which would accuse 2 peaks, instead of just one.
Anyone have an idea on how to work around this or any other method more reliable than taking the derivative of the signal?
Solved!
Go to Solution.

Well, we can only answer question based on the information supplied! The LabVIEW Mind Reading Toolkit is still in development.
Your application is one where parallel loops may be valuable. In the acquisition loop you read data from the data acquistion device at a rate which optimizes the DAQ perfomance (the >= 2k points you mentioned). The data is transferred to an analysis loop via a queue. In the anaylsis loop you can put the data into a shift register. When more data is available from the Acquisition loop, dequeue it and append it to the data in the shift register. The Duty Cycle section will find two consecutive rising edges and the falling edge between them ( the 10 ms segment). It calculates the duty cycle for that segment. Then it uses the second of the rising edges as the first rising edge for the next segment. Repeat until duty cycles have been determined for all segments.
There are a lot of details which can be imprortant in a process like this. Many of them are dependent on other things you have not specified. What will be done with the duty cycle values? Is the raw data to be displayed? Saved to file? Discarded after the duty cycle is measured? How long will the process continue? How much data can accumulate?
Lynn

How can I vary a PWM´s duty cycle inside a while loop?

Hi,
I'm using the "Generate Pulse Train.vi" to generate pwm signals in counters 0 and 1 in order to drive a DC motor both ways.
The problem is, I need to control the movement of the dc motor with my PI controller which is inside a while loop. I've tried letting the "generate pulse train.vi" outside the while loop, but the problem is, it only changes the value of the duty cycle when the loop is stopped. I also tried putting it inside the loop, but then it doesn't even work.
So, how can I vary a PWM´s duty cycle inside a while loop?
I'm attaching the VI with the PI controller.
Thanks for your help!
Guilherme
Attachments:
controleValvula.vi ‏332 KB

Here's some code I threw together a while back to change a duty cycle on the fly. It generates a fixed 5KHz or 25KHz frequency depending on laser selection, then allows duty cycle to be changed continously. Maybe you can use the premise of it for your application.
~~~~~~~~~~~~~~~~~~~~~~~~~~
"It’s the questions that drive us.”
~~~~~~~~~~~~~~~~~~~~~~~~~~
Attachments:
Pulse_Width_Modulator.llb ‏197 KB

How can I measure a 0% or 100% duty cycle signal ?

I want to measure the duty cycle of an input signal using a counter of a 6030-E board.
I work with a PXI Rack under Labwindows/CVI.
My program already works properly for duty cycle between 1% and 99%, but it is not able to detect 0% duty cycle (ie : signal to ground), nor 100% duty cycle (ie : signal to power supply).
The problem is I don't understand how the counter works in such a situation (it cannot detect any edge, as long as the signal is continuous 0V or continuous 12V).
Please have a look on the following code :
1- First, the counter is configured
// Reset Compteur
i_Status = GPCTR_Control(iDevice, iCptID, ND_RESET);
//Definition du type de mesure du compteur (mesure temps impulsion)
i_Status = GPCTR_Set_Application (iDevice, iCptID, ND_SIMPLE_PULSE_WIDTH_MSR);
//Definition de la vitesse d'echantillonage (20 Mhz)
i_Status = GPCTR_Change_Parameter(iDevice, iCptID, ND_SOURCE, ND_INTERNAL_20_MHZ);
//Definition du signal a mesurer (defaut)
i_Status = GPCTR_Change_Parameter (iDevice, iCptID, ND_GATE, ND_DEFAULT_PFI_LINE);
// initialisation du compteur
i_Status = GPCTR_Change_Parameter(iDevice, iCptID, ND_INITIAL_COUNT, 0);
// Preparation du compteur avant de l'armer
i_Status = GPCTR_Control (iDevice, iCptID, ND_PREPARE);
2- Then, every 10 ms, the value of the counter is read, so that I can calculate the duty cycle...
i_Status = GPCTR_Watch(iDevice, iCptID, ND_COUNT, ul_val_cpt);
3- ...and the counter is armed again for the next reading
i_Status = GPCTR_Control(iDevice, iCptID, ND_ARM);
When duty cycle changes from x% to 0% or 100%, the counter always keep the value corresponding to x%.
Even if I reset the counter between each measurement, it keeps this value ! I don't understand how it is possible.
How can I know that the counter didn't see any edge, and so that duty cycle is 0% or 100% ?
Thank you in advance for your help !
FraB

Hi,
Just have a look at this link, it can be interesting for you...
http://forums.ni.com/ni/board/message?board.id=40&message.id=2161&requireLogin=False
Regards
DD

How to generate a pwm whose duty cycle has to be varied depending on the frequency of the input trigger??

Sir/madam,
I am quite new to the Labview FPGA module.
I am currently working on an application where i have to generate a pwm to control the ON time duration . The pwm ON time depends on the frequency of an input signal.I want to retrieve the ON time value from a lookup table which contain the duty cycle values for the pwm at different frequencies of the input.This input also has to work as a trigger. The input is pulsed and the trigger has to generate the pwm at every rising edge. I am using a PCI 7831R- RIO series. I am urgently in need of some help and i have hardly a couple of weeks before i meet the deadline.
I am trying hard to learn the basics from the shipping examples but not able to quite make my vi work.
Kindly lend a helping hand and i would be very grateful to anybody who can help. Thanks a lot in advance.
Do ask in case of any clarifications required. I think i have explained my problem quite well.

Hello Manu,
You can refer
Developing a PWM Interface using LabVIEW FPGA or PWM Output with LabVIEW FPGA
How this helps.
Best Regards,
Hardik Asawa
AE
National Instruments
Message Edited by Hardik Asawa on 05-05-2010 12:46 AM

Kernel Panic - invalid backlight duty cycle - after upgrade from 10.5.2 on macbook air A1237

Here is the short version. I bought an older orignial Macbook Air Model A1237. The hinges had been damaged, and the screen would not display correctly - it had lines all across it and you could not see what you were doing. Anyway - I replaced the screen, hard drive, logic board, upper case, pretty much everything in sucession in an effort to get the MBA up and running again and get rid of the kernel panic I keep getting, all Apple replacement OEM parts. I bought a replacement screen - making sure I checked compatibility etc.. but when it started up I felt great perfect view - all was good - then it kernel paniced. I finally figured out that if I turned up the backlight manually all the way to max or if the ambient sensor made the backlight go to max - these were the only time I get a panic. Otherwise it runs perfeclty. The odd thing is I bought the original MBA disc that would have came with the MBA brand new - and if I wipe the hard drive and install leopard 10.5.2 from the dics and do not update anything - it works 100% perfectly no kernel panic at all. If I updgrade beyond the 10.5.2 I get the panic back. So that tells me its not the hardware, and I have confirmed the hardware and firmware are all up to date, as I was hoping it would be that easy a fix of updating the firmware. I have tried everything - googled everything - I am at the end of my rope on this one - please help.
In addition to all the repair work - i have tried test user, upgrading to snow leopard and lion, taking to the apple store, everything I can do , with no solid answer - the apple store told me it was hardware. But if it was then 10.5.2 should generate the panic as well. There are lots of articles and posts on other forums on this very issue - usually surrounding having the MBA display repaired and then they started getting the panics thereafter - but no one has ever recieved an answer either at all, or that works.
Here is the KP log below - please let me know your thoughts - id like to upgrade to lion to get the most out of the MBA - any help is appreciated - - - - - heres the log - - - - ( the reason the BSD states at loginwindow is the ambient sensor at that time kicks in and creates the panic ):
Interval Since Last Panic Report: 3873 sec
Panics Since Last Report:          1
Anonymous UUID:                    3A665154-0D6B-4EDF-8F76-80C322CF134A
Mon Aug 27 23:04:07 2012
panic(cpu 0 caller 0x2E42320C): "IG: Invalid backlight duty cycle value"@/SourceCache/GraphicsDrivers/GraphicsDrivers-5.48.6/Common/GLKernel/Inte l/IntelIntegratedFramebuffer/IntelGMAX3100FB.cpp:7065
Backtrace (CPU 0), Frame : Return Address (4 potential args on stack)
0x2e3dbaa8 : 0x12b4c6 (0x45f91c 0x2e3dbadc 0x13355c 0x0)
0x2e3dbaf8 : 0x2e42320c (0x2e431258 0xa4aa 0x2e3dbb18 0x0)
0x2e3dbb18 : 0x2e425434 (0x3af6c00 0x5f40 0xe 0x0)
0x2e3dbb68 : 0x2e4d2283 (0x3e75000 0x0 0x626b6c74 0x5f40)
0x2e3dbbd8 : 0x2e3f9769 (0x4639e00 0x4107280 0x3a6ace0 0x80)
0x2e3dbc08 : 0x2e3f724c (0x48f2a00 0x4107280 0x3a6ace0 0x80)
0x2e3dbc38 : 0x2e3f785d (0x48f2a00 0x80 0x2e3dbc68 0x3f158d)
0x2e3dbc58 : 0x2e3f71db (0x48f2a00 0x80 0x2e3dbc88 0x3f0942)
0x2e3dbc78 : 0x2e3f9475 (0x48f2a00 0x430c640 0x3a6ace0 0x80)
0x2e3dbca8 : 0x2e3f92b9 (0x48f2a00 0x430c640 0x3a6ace0 0x80)
0x2e3dbd28 : 0x440edf (0x48f2a00 0x3feb880 0x44 0x11e7de)
0x2e3dbd78 : 0x18b71a (0x48f2a00 0x3fea900 0x44 0x407c7c0)
0x2e3dbdb8 : 0x12d4d6 (0x3b92090 0x407c79c 0x2e3dbdf8 0x11f1c6)
0x2e3dbdf8 : 0x1264fa (0x3b92000 0x392e984 0x408226c 0x0)
0x2e3dbf08 : 0x198fa3 (0x2e3dbf44 0x0 0x0 0x0)
0x2e3dbfc8 : 0x1a1cfa (0x398d120 0x0 0x1a40b5 0x3dc0c80)
          Backtrace continues...
      Kernel loadable modules in backtrace (with dependencies):
         com.apple.driver.AppleBacklight(1.6.0)@0x2e4d0000->0x2e4d3fff
            dependency: com.apple.iokit.IONDRVSupport(1.7.3)@0x2e435000
            dependency: com.apple.iokit.IOPCIFamily(2.6)@0x2e2d5000
            dependency: com.apple.iokit.IOGraphicsFamily(1.7.3)@0x2e3f5000
         com.apple.driver.AppleIntelGMAX3100FB(5.4.8)@0x2e41c000->0x2e434fff
            dependency: com.apple.iokit.IOPCIFamily(2.6)@0x2e2d5000
            dependency: com.apple.iokit.IOGraphicsFamily(1.7.3)@0x2e3f5000
            dependency: com.apple.driver.AppleSMC(2.3.1d1)@0x2e412000
            dependency: com.apple.iokit.IOACPIFamily(1.2.0)@0x2e2ec000
         com.apple.iokit.IOGraphicsFamily(1.7.3)@0x2e3f5000->0x2e411fff
            dependency: com.apple.iokit.IOPCIFamily(2.6)@0x2e2d5000
BSD process name corresponding to current thread: loginwindow
Mac OS version:
9L31a
Kernel version:
Darwin Kernel Version 9.8.0: Wed Jul 15 16:55:01 PDT 2009; root:xnu-1228.15.4~1/RELEASE_I386
System model name: MacBookAir1,1 (Mac-F42C8CC8)
System uptime in nanoseconds: 58935778708
unloaded kexts:
(none)
loaded kexts:
com.apple.driver.AppleHDAPlatformDriver          1.7.1a2 - last loaded 45739893296
com.apple.driver.InternalModemSupport          2.4.0
com.apple.iokit.IOBluetoothSerialManager          2.1.9f10
com.apple.filesystems.autofs          2.0.2
com.apple.driver.DiskImages          199
com.apple.driver.AppleHDAHardwareConfigDriver          1.7.1a2
com.apple.driver.AppleHWSensor          1.9d0
com.apple.driver.AppleUpstreamUserClient          2.7.5
com.apple.Dont_Steal_Mac_OS_X          6.0.3
com.apple.driver.AppleHDA          1.7.1a2
com.apple.driver.ApplePlatformEnabler          1.0.2d1
com.apple.driver.AppleGraphicsControl          2.8.15
com.apple.driver.AppleIntelGMAX3100          5.4.8
com.apple.iokit.IOSCSIArchitectureModelFamily          2.1.1
com.apple.driver.AppleIRController          113
com.apple.driver.AirPortBrcm43xx          367.91.22
com.apple.kext.AppleSMCLMU          1.4.5d1
com.apple.driver.AppleLPC          1.3.1
com.apple.driver.AppleTyMCEDriver          1.0.0d28
com.apple.driver.AppleHDAController          1.7.1a2
com.apple.driver.SMCMotionSensor          2.1.1d2
com.apple.driver.AudioIPCDriver          1.0.6
com.apple.driver.ACPI_SMC_PlatformPlugin          3.4.0a17
com.apple.driver.AppleBacklight          1.6.0
com.apple.driver.AppleIntelGMAX3100FB          5.4.8
com.apple.driver.AppleUSBTCButtons          1.7.4f1
com.apple.driver.AppleUSBMultitouch          189.35
com.apple.driver.AppleUSBTCKeyEventDriver          1.7.4f1
com.apple.driver.AppleUSBTCKeyboard          1.7.4f1
com.apple.driver.BroadcomUSBBluetoothHCIController          2.1.9f10
com.apple.driver.AppleUSBMergeNub          3.5.2
com.apple.driver.XsanFilter          2.7.91
com.apple.iokit.IOATABlockStorage          2.0.6
com.apple.driver.AppleUSBHub          3.4.9
com.apple.driver.AppleFileSystemDriver          1.1.0
com.apple.iokit.IOUSBUserClient          3.5.2
com.apple.driver.AppleAHCIPort          1.7.0
com.apple.driver.AppleIntelPIIXATA          2.0.1
com.apple.driver.AppleUSBEHCI          3.4.6
com.apple.driver.AppleUSBUHCI          3.5.2
com.apple.driver.AppleEFINVRAM          1.2.0
com.apple.driver.AppleRTC          1.2.3
com.apple.driver.AppleHPET          1.4
com.apple.driver.AppleSmartBatteryManager          158.10.5
com.apple.driver.AppleACPIPCI          1.2.5
com.apple.driver.AppleACPIButtons          1.2.5
com.apple.driver.AppleSMBIOS          1.4
com.apple.driver.AppleACPIEC          1.2.5
com.apple.driver.AppleAPIC          1.4
com.apple.security.seatbelt          107.12
com.apple.nke.applicationfirewall          1.8.77
com.apple.security.TMSafetyNet          3
com.apple.driver.AppleIntelCPUPowerManagement          76.2.0
com.apple.BootCache          30.4
com.apple.iokit.IOSerialFamily          9.4
com.apple.driver.DspFuncLib          1.7.1a2
com.apple.iokit.IO80211Family          216.1
com.apple.iokit.IONetworkingFamily          1.6.1
com.apple.iokit.IOHDAFamily          1.7.1a2
com.apple.iokit.IOAudioFamily          1.6.9fc5
com.apple.kext.OSvKernDSPLib          1.1
com.apple.driver.IOPlatformPluginFamily          3.4.0a17
com.apple.iokit.IONDRVSupport          1.7.3
com.apple.driver.AppleSMC          2.3.1d1
com.apple.iokit.IOGraphicsFamily          1.7.3
com.apple.iokit.IOUSBHIDDriver          3.4.6
com.apple.driver.AppleUSBBluetoothHCIController          2.1.9f10
com.apple.iokit.IOBluetoothFamily          2.1.9f10
com.apple.driver.AppleUSBComposite          3.2.0
com.apple.iokit.IOStorageFamily          1.5.6
com.apple.iokit.IOAHCIFamily          1.5.0
com.apple.iokit.IOATAFamily          2.0.1
com.apple.iokit.IOUSBFamily          3.5.2
com.apple.driver.AppleEFIRuntime          1.2.0
com.apple.iokit.IOSMBusFamily          1.1
com.apple.iokit.IOHIDFamily          1.5.5
com.apple.driver.AppleACPIPlatform          1.2.5
com.apple.iokit.IOACPIFamily          1.2.0
com.apple.iokit.IOPCIFamily          2.6

So I found a post on a random forum that offered a fix that I have tried and it worked. Background: I had a cracked LCD screen on a A1237, and I replaced a new screen and a battery. I started getting kernel panics when the brightness went to the highest level. Anyways, what you do is you need to get this file from a apple os x 10.5:
/System/Library/Extensions/AppleIntelGMAX3100FB.kext
then:
Install the .kext file you just grabbed by dragging it into Kext Utility (which can be downloaded here: http://cvad-mac.narod.ru/index/0-4)
then:
Shut down the machine. Reset SMC and PRAM (SMC: http://support.apple.com/kb/ht3964, PRAM:http://support.apple.com/kb/ht1379)
and the problem is fixed. If you google a bit, you can find an os x 10.5.2 AppleIntelGMAX3100FB.kext file at to use.
The original fix I found was posted here:
http://forums.macrumors.com/showthread.php?t=880800
Edit:
Just to clarify, my mac book air is running snow leopard 10.6.8, and I inserted the file from a 10.5.2. The fix completely eliminated the problem, now I can turn the brightness to max without the kernel panic.

Sine, Square & Sawtooth sweep generation with variable duty cycle/rise time & fall time

Dear All !
I request and need some candid advices on the subject issue keeping in view the following notes:
1) I am a novice in LabView.
2) I was an average Electronics Engineering graduate who graduated about 9 years ago and since then I have not been involved in Electronics Engineering.
I have undertaken a task or generation of Sine, Square and Saw Tooth wave forms. All these waveforms are to be frequency swept form 1 Hz to 100 kHz. The amplitude of all these waveforms should be able to be adjusted. The duty cycle of Square Wave should also be adjustable (or better be able to be swept). Likewise the rise time and fall time of sawtooth wave should also be adjustable (or better be able to be swept).
I am considering other options as well but wanna try it on LabView.
I wish to ask that is it possible to execute this task in Labview 7.0? If possible then considering the para 1 & 2 above, is it possible for me to finish this task in 15-20 days if I work on this for about 3 hours a day? If not then what can be reasonable estimate?
I will be extremely grateful if you people can offer advice on whole project or part(s) of it.
Thanking you in advance and requesting urgent response(s).
Solved!
Go to Solution.

Check this thread.
I did some similar coding, it might be usefull to you.
http://forums.ni.com/ni/board/message?board.id=170&thread.id=493477&view=by_date_ascending&page=1
I am using ver 9.0 though.
If you work 3hr /day for 2 weeks you might as well finish book basics 1& 2 and than can do whan you need in a breeze, couple of hours.
Good luck

Excise duty getting calculated on freight value

Hi frnds,
I have an excisable material and the freight charge (FRA2) for this material.Tax procedure is TAXINN.
My issue is - during MIRO the excise duty is calculated on the material as well as on the freight charges. My client does not want excise duty to be calculated on freight charges.
Do I have to look the config for pricing schema or anything else.
Need your advice...
Regards,
Sachin Narvekar

Hi,
As per taxation , on Freight there will be always Service Tax, so create a Service Tax code and assign in MIRO with Planned Delivery Cost. If your vendor is same for material as well as Frt, if possible create a new vendor code for Frt as service vendor.
Rgds,
Vikas Mayekar

Using labview cosimulation, how to control PWM duty cycle in multisim

I am new to using Multisim with LabVIEW using cosimulation. I want to ask if there is a PWM component in Multisim that can have its duty cycle be controlled using LabVIEW? I have an algorithm in LabVIEW that outputs duty cycle values from 0 to 1, representing duty cycle percentages.
How do I control the PWM duty cycle in Multisim using LabVIEW cosimulation?
Many thanks,
SPECTRE
Solved!
Go to Solution.

Hi Spectre,
In Multisim, search for the parts base on functionality, there are some PWM models in the database. Have a look at this knowledge base if you don't know how to search for parts:
http://digital.ni.com/public.nsf/allkb/7309A5CABC677296862577ED006EC99E
Aslo, have a look at this knowledgebase:
http://digital.ni.com/public.nsf/allkb/EF391C48CF71AE4F862571B900644F84
This article shows how you can get Mutlisim and LabVIEW to co-simiualte:
http://www.ni.com/white-paper/13663/en
I hope this helps
Tien P.
National Instruments

Problem to measure 0% and 100% duty cycle of a PWM.

Hi,
I am using counters of USB-6341 to measure duty cycle of PWM just by following the example 'Meas Duty Cycle-Buffered-Finite.vi'. It works almost all the time. However, when the duty cycle of a input pwm is 0 or 100%, the DAQ can't read anything, in another word, it can't measure 0 or 100% duty cycle.
How to modify that?
Thank you very much :-)
Nan

That's the thing about PWMs, you never really know if the PWM is 0% or 100%.
Let's say we have a 50% duty cycle, at 1/2Hz. So low for 1 second, high for one second right? What if we run at 1/20Hz, so low for 10 seconds high for 10 seconds. Or is this a 0% duty cycle for 10 seconds, and a 100% for 10 seconds?
A true PWM read will never be 0% or 100% it will just keep waiting until the trigger is seen, and recalculate the frequency and duty cycle of it. The solution to your problem is for you to define a duration to watch for a change, and if one isn't seen, then you can define 0% or 100% appropriatly.
So I would recommend taking your duty cycle like you normally are, and then at the same time watch the digital signal for however long you want, if the digital line does not change state, then output 0% if it is low and 100% if it is high and ignore what ever duty cycle you read. But if the digital line does change state, then use the read duty cycle as the actual value.
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How to convert a number to duty cycle (FPGA)

Hi
I want to convert a numerical number to a duty cycle value in FPGA module so I could use it to generate a PWM signal for the numerical value.
I tried dividing it but it shows an error in FPGA as it would produce a float value. I tried even the example of scaled division but the quotient is rounded of to 0 (I wanted to convert an output by multiplying 10/36).
In my project the 100% duty cycle is 360 degrees and 0% is 0 degrees of the motor shaft rotation.
Please help me I need to use it for my project.
Thank you
Dinesh

I am not exactly sure how your duty cycle is setup, but here is a way we have used a number to create a PWM in our FPGA.
If you have 360 deg. then I would guess you want to create a PWM duty cycle that is some fraction of 360, say "number"/360. You could use a for loop where 360 is wired to the "N" and then your "number" can be compared to the current loop count. That comparison would be true/false which could triger a DIO to be high or low. Therefor, if (loop count) < "number" then DIO is HIGH, if (loop count) >= "number then DIO is LOW. This would send out a PWM that has a duty cycle of "number"/360, (multiply by 100 to get in %)
I hope this helps.
--Alex--

Duty Cycle - Calculations

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