Laser pulse counter in FPGA

Dear guys,
i have a laser pulses that i wont to measure the time between the start and end pulse via FPGA.
i am not familiar with FPGA but because of the cost i am forced to use it. my fpga D70.
so if you guys got any info answer will be so greatful

sam432,
Do you have an FPGA from NI? What is the model number? D70 doesn't sound like any NI FPGA model numbers. You will need to have an NI FPGA if you want to use the LabVIEW FPGA Module.
If you're asking in general how this is done, typically you would use a counter to determine the period of the square wave. More information about your laser and what NI hardware you might be using would be helpful.
Robert B
Applications Engineer
National Instruments

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First off, I am very new to using labview. I am trying to complete a project a former employee was working on.
For a quick background on what I am working with, I am using a NI DAQCard-6036E connected to a SC-2345. The SC-2345 is then connected to a load sensor, Omron R88D servo driver, and an omron servo motor. The servo motor has a incremental encoder with a resolution of around 2048 pulses per revolution. My labview program includes a counter that records the data from the encoder on the servo motor. I have been able to get accurate data when testing through the measurement and automation program by manually turning the motor. Also when running through the specific DAQ assistant I am using for my counter, I am getting correct readings when manually turning motor. Once I run my complete program, instead of getting 2048 pulses per revolution, I am getting between 34000-36000 pulses per revolution. The most logical assumption is that I am getting vibration in the motor itself or some sort of noise is interfering with my signal. I first attempted to change any possible settings through the omron servo driver that might reduce any vibration in the motor. I attempting changing the rigidity settings, turning on and off the auto-tuning function, and a few other settings specified by the user manual that might cause vibration. If I turn the rigidity settings as low as possible, I am able to get around 2000 pulses per revolution, but the data is very sporadic. Also, my equipment needs to be very rigid, and with the lowest rigidity setting for the servo driver, I am able to almost stop the motor with minimal force. My equipment needs to be able to travel at a near constant speed with fluctuations of up to 200 N of force. Any suggestions on which direction I should go in finding a countermeasure?
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Go to Solution.

The model number of the servo motor is R88M-W10030L. The servo motor rotates at a constant speed. The program is designed to drive the servo motor connected to a ball screw in one direction. Once the load sensor reaches a desired load, it will reverse at a constant speed until no load is on the sensor. Throughout, it records load vs. displacement. I have found a few things that will alter the pulses counts. If you apply resistive pressure on the servo motor while it is rotating, the pulse output will vary. Also when you apply pressure to the casing of the servo motor itself, the pulses will often jump around. I was almost certain my false pulses were caused by vibration. After have no success adjusting settings to reduce vibration(according to the user manual), I ran the program while moving around several wires to see if any were loose, etc... After applying force to the power lines and encoder cable, the program ran several times with an average of 2000 pulses per revolution and would actually subract pulses while going in reverse(what I want it to do); Although the average was around 2000 pulses per revoltion, i saw positive and negative jumps in pulse counts while traveling forward at constant speed. Today I re-wired the equipment, seperating as many wires as possible. After the re-wire, the equipment/program is back to sending 34000+ pulses per revolution, and does not subract pulses while reversing. I have read the 'Using Quadrature Encoders with E Series DAQ Boards' article. Referring to the article, I am running similar to "method 1". I am already using a signal conditioning box, but have the counter data run directly through. Do you believe running the signals through a SCC-CTR01 might solve the problems?

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I need a idea in how to do a Pulse Counter.
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I am using CDAQ with a NI9229 4 Channel analgoue input card.
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pulse count 2.PNG ‏20 KB
pulse count.PNG ‏19 KB
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I think I know what the problem is now but don’t know a way around it.
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Here is an example vi of how I am reading the pulses and some data processing I am doing with the signal. I have built in a totalised pulse counter to compensate for the maximum of 65535 pulses that can be counted by the module - so I do not miss pulse counts on reset.
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I need to know a USB module which can be used for pulse counting. The pulses are generated from an encoder attached with an stepper motor. It generates 15 pulses per step.Pulse amplitude is 0 to 5V. I am using a compact DAQ system (ni 9178).

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Best Regards,
John Passiak

Cannot Find Pulse Width Modulation(FPGA, Use in SCTL)

Hello All,
Can someone tell me where I can find Pulse Width Modulation (FPGA, Use in SCTL).vi? I couldn't find it in LabVIEW Example Finder.
Thanks
Message Edited by John Edwards on 02-01-2009 09:30 PM
Solved!
Go to Solution.

Here it is...
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Pulse Width Modulation (FPGA, Use in SCTL).vi ‏43 KB

Pulse count with a 9401 modules (cDAQ-9172 system)

I'm trying to do a pulse counting by a 9401 module in a cDAQ-9172 system. I have three 9401 modules . One of them is working as a trigger (start-stop count) and the other two (in slot 5 and 6) are for counting pulses from the 2 meters. It looks like a simple task but my problem is that I am counting always 3 to up to15 pulses less than my reference counter. everything points out to a task in my program is causing a delay. The question is where or what is causing such a wrong counting
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COOMET Comparison DN80 short.vi ‏737 KB

First for triggering with cdaq you must use the 9405 or 9406 (for analog triggering or 9401 for digital triggering) module in slot 5 and 6 - look in following link. Signals are routed with the chassis PFI Lines and only available at Slot 5 and 6.
http://digital.ni.com/public.nsf/allkb/851828B06A20E01B862571DA0005591A?OpenDocument
http://digital.ni.com/public.nsf/websearch/EFD808DC883F095186257170005A634D?OpenDocument
Then the other moduls in other slots can be configured with these pins for triggering. When you wants triggering on both edges you can look in following link:
http://forums.ni.com/ni/board/message?board.id=170&message.id=248456&requireLogin=False
Best Regards

Pulse Counter using LM3S8962

Hello,
I need the display and control this following points on EKK-LM3S8962 ARM board
Generate the pulse signal.(as shown in excel file)
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At every 34 pulse I need to synchronize the cam single (as shown in excel file).
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CrankSignals_Ref.xls ‏183 KB

I also have "NI USB-6341, X Series DAQ (16 AI, 24 DIO, 2 AO)," but I am trying to make a pulse counter for analog signal
I tried to use the "get waveform component" and can't get it to work. There is an error (regarless if I use analog or digital version of the get waveform component function). I am using the "simulate signal" function since I haven't gotten the circuit built yet.
The attached vi is far as I can go with what I know. Trying to learn more...
I really appreciate your help so far. At first, I thought creating a pulse counter for analog signal should be easy in labview...
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Pulse counter.jpg ‏79 KB

Pulse counting with voltage input

Im using compact field points analog I/O (AI-112) to measure the frequnecy of an anamometer.
Basically the sensor is just a switch that open/closes at a frequency which gives 1 pulse per second (1Hz = 1.25MPH).
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to handle this measurment. Im having trouble finding the right VI's to do the job. Any suggestions for
possible ways to count the pulses/ measure the frequncy would be appreciated.

Hello cfpboy,
I have a question about your signal first. How long does your signal remain changed when a pulse occurs? Does the signal stay "high" for 1 full second and then go "low" or does it pulse "high" once a second and then immediately return to "low". If it stays "high", then you could simply poll the input in a LabVIEW Loop set to occur once a second. You could then store the value in a shift register, and compare the current value to the previous value. If they are different, then the state has changed, and you could then increment your software counter. As you are using an analog input module, you will want to convert your voltage level to a "digital state" by checking if it is above or below a specified level.
One drawback of this approach is long term phase shifting as well as the possibility of reading while in a transition state. This could potentially throw off your measurements. As you are using LabVIEW Real Time, you can slightly mitigate some of these problems by utilizing a LabVIEW Timed Loop instead of a normal Loop.
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Jonathan C
Staff Application Engineering Specialist | CTD | CLA
National Instruments

Laser pulse counter in FPGA

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