Myrio tachometer implementation

I am building an automotive data logger using a myrio and am looking for the best way to get tachometer RPM data onto the myrio.
The output sinal I have is a 12V square wave. So if I were to using an analog read It would need some kind of voltage divider to scale it to about 5V. But can an anlog input have a high enough frequency to not miss any data. I believe at red line of the max frequency I will need to read is about 250Hz. So I would need to log at over 500 Hz and still have enough overhead for other functions I have in my code.
I would guess a better way to do this would be using the fpga to find time between pulses to calculate rpm. But I am not sure how to wire this with the existing 12V tach signal.
Another option would be a seperate magnetic or optical tach device that a mount on my engine which would be a last resort effort if I can not using the exisiting signal.
Any suggestions to accomplish this would be greatly appreciated!

Hey Cyotani,
I found this example that I thought could be useful to give yourself an idea about how could you get started with the application:
"Decoding Tachometer Signals Using CompactRIO/LabVIEW FPGA"
http://www.ni.com/example/27326/en/
Also here a good article to take in count some considerations about it:
"Decoding Tachometer Signals Using CompactRIO and LabVIEW FPGA"
http://www.ni.com/white-paper/3230/en/
Hope this can be helpful,
Regards!
Daniel C.

Similar Messages

Tachometer RPM Errors

I am trying to use my tachometer and LabVIEW (V11) to give me the rpm of a wheel/hubmotor system. Using a USB 6211, the ctr0 counter pin, the OAT Digital Tachometer vi and a function generator (generating a square wave at 2Vpp, 50% duty cycle and 1-25 Hz) is giving me very big errors. For instance, there are times where the setup will say that the rpm's are extremely large, negative, NAN or infinity. Also, when I increase the frequency, there are regions that it will increase the rpm and others where it will decrease it. I have also added the loop timing delay to somewhat account for the likely delay that will be incurred when this code is inserted into the larger program that will have a lot more running along side this, and this seems to alter the performance. Any help would be appreciated.
Thanks.
Attachments:
Tach_Block.png ‏15 KB
Tach_Block.png ‏15 KB
FailedTach.vi ‏67 KB

Katie,
Thanks for your response, and I apologize that it has taken me a while to get back to you.
I tried incorporating the OAT Build Digital Tacho Info VI, and received the same results.
In response to the second half of your reply, I did use MAX and confirmed that the count was incrementing at the frequency of the signal from the function generator. I have attached the VI that will be using the tachometer to get a wheel's rpm/ground speed to monitor performance so that you can get a better look at all that is going on. The other VI was used to test LabVIEW rpm/groundspeed methods outside of the main program, which is not currently complete enough to run. Additionally, the tachometer will need to be sampled continuously at a rate of 7kHz. The wheel will only ever have a ground speed of 0 to 50 kph (0 to 33 mph) which means that a point will occur with frequency between 22 and 24 Hz (24 and 26 in wheel).
My biggest concern is finding a method of calculating the rpm/groundspeed that will not slow down the rest of the program. Of the other sensors, three will also be sampling continuously at 7kHz and two at only a few Hz.
For the attached VI, you only really need to look at the "True" case for the two top most case structures, as all other cases are basically copies of this case. Also, there are some subvi/support VIs that LV will look for, which can be ignored since they do not have anything to do with the tachometer implementation/problem.
Thanks again for the help,
CU-IMPULSE
Attachments:
Level 4 V8.vi ‏176 KB

MyRIO FPGA FFT Express VI timing analysis for multiple input mode - trying to perform fft's on a 3-axis accelerometer

Hi Everyone!
Project Background:
I've been working with the myRIO FPGA in an attempt to generate an application capable of sampling a tri-axis accelerometer and performing an fft on each axis. I've successfully developed an application for a single axis, but attempting to duplicate the code to sample the second and third axes in parallel results in an estimated 150% resource utilization for the tiny FPGA's LUT's. Additionally, I'm looking to avoid sequentially processing each accelerometer input using triggers and a single fft block because that reduces my fft update frequency significantly (e.g. I can't calculate another fft for input 1 until I calculate an fft for inputs 2 and 3).
After reading up on the fft vi, I'm thinking that I can use the M-interval input indexes / Continuous output indexes Input/Output Index Pattern mode. My thought is that I can edit the vi to remove any math that "recombines" these three vectors into a single fft, resulting in 3 separate fft's. I'm also hoping that this process requires less time than using the sequential method described above.
The Questions:
1. Has anyone done an fft on three inputs using the myRIO at sampling rates > 20kHz and fft sizes of 1024 or larger? If so, I may just be lacking some proper resource management.
2. Does anyone know where to find timing information on the M-interval input indexes / Continuous output indexes Input/Output Index Pattern mode? The manual only provides timing diagrams for singel channel / single input modes. I don't want to waste my time modifying the vi if it will still take 3x as long (assuming modifying the vi is even a possibility).
Further Information:
I already have an application written that samples the accelerometers at >20kHz and then performs the fft on the main processor, but now I'm looking to see if it is possible to perform all signal processing on the FPGA side. The processor performs decently enough, but the timing is not as consistent as I would like it to be. Lastly, I am aware that the myRIO itself has a built in accelerometer, but I need to mount the accelerometer in an environment where the myRIO would probably be damaged and definitely cannot fit.
Any thoughts are much appreciated! The excessive FPGA compile times for this thing make the old guess and check method less appealing.
-Chris

Hi Chris,
Thanks for posting and the detailed background on the project! To answer some of your questions:
1. The FFT Express VI does use a significant amount of space. The FPGA on the myRIO is somewhat limited space-wise. Your best option may to implement the FFT for 1 channel on the FPGA and the other two on the RT side.
2. I converted the FFT Express VI to a subVI and I am not sure if you can trim too much code from it. The subVI is also very complex so re-working it would be a significant amount of work. I could not find much documentation on M-interval input indexes / Continuous output indexes Input/Output Index Pattern mode timing.
I hope that this helps!
Thanks,
Frank
Application Engineer
National Instruments

How to implement start & stop ai triggers when # scans unknown

I can't seem to find an implementation example for this application.
Some are close but seem to have a big gap on close examination.
The application is to log an unknown number of samples for a
single rotation of a variable speed drum. The drum is connected
to a tachometer which generates 1 pulse per revolution and is the
trigger source.
The user will initiate the data collection and only a single
rotation's
worth of data need be collected and displayed.
The board is a PCI 6111E sampling a single input at ~2 Megahz.
All the examples I've found using a start and stop trigger depend
on knowing how many scans to acquire.
Is there any way to get around that? It seems so simple to
have a
start and stop pulse, a scan rate constant, and just get
the data out of a buffer. But it does not seem to be that simple
or am I missing something here?
There is also an issue with the identical tach signal being used
for both the start and stop trigger. I think that can be gotten
around by using a divide by n counter and feeding that to
trigger config vi but if anyone has any suggestions for that,
they would be greatly appreciated.
Gene Couch

I'm afraid I can't help you beyond that. We use NI boards and NI-DAQ library
of functions in custom control systems with software written in C++. I have
not had opportunity to use LabView. Sorry.
gcouch wrote:
>On 5 Jun 2000 09:38:46 -0500, "J. Wolters" >wrote>Thank
you for the response but I'm not sure what the DAQ_Rate function>is. With
LabVIEW 5.1 it does not appear in the DAQ pallette and I>cannot find it in
the example vi's. Do you know where it can be>found?>>>>>>Have you looked
that DAQ_Rate function? You should be able to use this function>>to obtain
your # of samples.>>>>>>gcouch wrote>>I can't seem
to find an implementation example for this application.>Some>>a
re close but
seem to have a big gap on close examination.>>The application>>is to log
an unknown number of samples for a >single rotation of a variable>>speed
drum. The drum is connected>to a tachometer which generates 1 pulse>>per
revolution and is the>trigger source.>>The user will initiate the data>>collection
and only a single>rotation's>worth of data need be collected and>>displayed.>>The
board is a PCI 6111E sampling a single input at ~2 Megahz.>> >>All the examples
I've found using a start and stop trigger depend>on knowing>>how many scans
to acquire.>>Is there any way to get around that? It seems>>so simple to>have
a start and stop pulse, a scan rate constant, and just>>get>the data out
of a buffer. But it does not seem to be that simple>or>>am I missing something
here?>>There is also an issue with the identical tach>>signal being used>for
both the start and stop trigger. I think that can>>be gotten>around by using
a divide by n counter and feeding that to>trigger>>config v
i but if anyone
has any suggestions for that,>they would be greatly>>appreciated.>>Gene Couch>>>

Generate sine waveform (myRio)

What is the best way to generate a 1khz sine signal on one of the analog outputs of the myRio device? I tried a timed loop and the Point by Point Sine Generation VI similar to the Electret Microphone demo or this post: http://forums.ni.com/t5/Academic-Hardware-Products-ELVIS/frequency-matching-problem-with-myrio/m-p/2... by Sammy_K. But the resolution is a problem. The frequency is not very accurate and with a dt of 100 uS and a 1Mhz Clock I only get 10 samples per period. A dt of 10 is too much load for the processor (the deivce does not respond anymore and needs to be restarted). Is there a better way of generating a 1khz sine output or do I need to do this within the FPGA somehow?
Solved!
Go to Solution.

Hey JulianR,
The thing to keep in mind is that each time you call the Analog Write express VI you write one data point to the analog output on the myRIO. The rate at which data is output is determined by the rate at which you loop runs. You can use a timed loop in LabVIEW to write analog output values at a relativly fixed loop rate and vary the value to generate a sine wave output.
I put together an example of doing just this (but using the value to set a PWM duty cycle rather than analog output) in this thread. You'd basically need to replace the PWM express VI with the Analog Output Express VI.
Finally as Marc67 mentioned you could implement the sine wave output in LabVIEW FPGA which would give you more control and let you use faster output frequencies. I'd start with the timed loop method and move to FPGA if you need faster output rates.
Let us know if you have more questions for us.
-Sam K
LabVIEW Hacker
Join / Follow the LabVIEW Hacker Group on google+

Problems using I2C on the FPGA of MYRIO

I made a real time program that talks the the PmodCLS; however, for my fpga program is must run under the fpga, and under communications there is some I2C functions however the documentation is just limited to the context help file. Attached you will find my working realtime code, and besides it are the fpga I2c functions that I don't quite understand, for it appears that you can only write one byte on the I2C bus, and I need to write more than that. See I2C fpga myrio problem.png.
Well in trying to run the following code in nibug06162015d.png on my rio I got an error shown in nibug06162015a.jpg, and when I click show error it pulls up IP SPI&I2C.lvlib:Write Data.vi which has a fifo which can change dynamically as shown in nibug06162015b.jpg and can be any of the following cases as shown in nibug06162015c.png I typically use fifos with one variable and I do know you can make a custom control to have multiple variables in one fifo. But, how do you make a custom control for something that changes like this fifo? I thought maybe a tab control with an enum ring in one of the tabs, but would that really work right? The files are in nibug06162015c.zip
This is some info about the I2C implementation that I am trying to use that does not have any documentation on.
I2C&SPI API v3.0.0.22 by National Instruments Released On: Mon, 07 Jan 2013 15:50:27 -0600 Author: National Instruments Copyright: Copyright (c) 2012, National Instruments Compatible LabVIEW Versions: >= 2010. Compatible OS Versions: ALL. Repository Name: NI LabVIEW Tools Network
I tried another approach by trying to use the I2C engine, as an subvi. However, that generated so many errors I do not know what to do. First I added the engine shown in nibug06172015a.jpg to nibug06172015c.png and saved it as a subvi which I called in nibug06172015b.png and trying to run it gave me the following errors in nibug06172015d.jpg These files are in nibug06172015.zip
Attachments:
i2c fpga myrio problem.png ‏139 KB
nibug06162015c.zip ‏407 KB
nibug06172015.zip ‏1217 KB

First, I tried the i2c express vis which did not go well, but luckly the PMODCLS also supports serial coms. So the UART express vis only configure the serial port and write/read to the serial port using standard visa calls. Which turns out to work, so it is possible to run a rt program on the my rio and call a program loaded in the fpga and obtain output from it. Here is my final working program.
Attachments:
RTMain2.png ‏495 KB
RT Main3.png ‏433 KB
Hbridge Motor Controller2.png ‏314 KB

Stepper position control with myRIO

Hello,
I am developing a position control system to move a linear stage back and forth using a stepper motor (file 1). The stage will ultimately need to follow the motion path set out in a function that I have defined (file 2).
I have been able to get the motor to move using a Big Easy Driver from Sparkfun (file 3), sending it a PWM signal from one myRIO pin, and setting another pin on the myRIO to high or low in order to establish the direction. From what I understand, each low-to-high transition in the PWM signal causes the motor to take one step (or microstep). Therefore the PWM frequency is equal to steps/second, the motor speed. Using timed loops along with this information, I am able to control how many rotations the motor performs at a constant speed.
However, I would like to be able to count steps, so that I can give the motor a position (number of steps to take from some defined "home") and it will go there, and vary speed accordingly to get there and ultimately follow my function. I will apparently need to implement some sort of PID control eventually, in order to accomplish this task. Right now I would just like to know how I can keep track of the position of my motor and control it that way.
I greatly would greatly appreciate any advice on how to implement this process.
Best,
E
Attachments:
Stepper_PK244-02AA.pdf ‏764 KB
PositionFunction.png ‏133 KB
BigEasyDriver_A4988.pdf ‏383 KB

Hi E,
How are you implementing PWM with the myRIO? Are you just using the myRIO express VI or are you writing your own code?
Also, just as a heads up, the Academic Hardawre Products page is a little more specific to the myRIO and is monitored by NI Developers who work with that device. If you post this question there, you may get a better response.
Ryan K.

MyRio analog input

Greetings,
I am new to NI and I have a question about the setting the timing on the analog inputs. I want to set up a clock (DIO output) and in addition, have ever clock rising edge initiate a single A/D conversion. Is this possible with the MyRio?
The background is I have a device with a string of sensors that will output a analog value every time I send in a clock, therefore I need to digitize the analog signal synchronized with the clock.
In addition, if someone has found documentation other than the manual, I would appreciate your sharing.
Thanks for the help,
Frank

Hi Frank,
Welcome to the forums! What you want to do is definitely possible with the myRIO. You have a few options available to you:
If you have the ability to upgrade to LabVIEW 2014, the myRIO 2014 toolkit includes new Interrupt Express VIs. You specify a condition (in your case, a rising digital edge) and a callback VI that executes when this condition is met. The best way to learn about how this works is to take a look at the examples in Example Finder (Help»Find Examples»Toolkits and Modules»myRIO»Interrupt Handling.lvproj.
If you don't have the ability to upgrade to LabVIEW 2014, you could implement something similar yourself by having a loop wait for a rising edge on a digital line by using the Digital Input Express VI and then doing the analog measurement. This method would introduce some jitter because of the overhead associated with the Express VIs. An example snippet of this is below. If you do have access to the FPGA module, I would recommend implementing this logic on the FPGA instead (further below).
Using the FPGA module to do the triggering would give you better results because of the tighter timing capabilites of the FPGA as compared to the Express VIs. The logic would be mostly the same on the FPGA as it is on the real-time except for the appropriate VIs swapped around:
Here, we are waiting for a rising edge on a digital line and then placing the data from the analog channel in a to provide this data to the host (real-time) application.
If you want absolute control over the synchronization of the AI to the clock, I would recommend implementing the logic in FPGA (2013 or 2014). If your application has a little leeway in terms of timing, the Express VIs (2013) or Interrupt Express VIs (2014) would work for you.
Let us know if you have any questions!
Best Regards,
Matthew B.
Applications Engineer
National Instruments

How do you convert the encoder counts to RMP of the motor using a myRIO in LabVIEW?

My intent is to gain hardware interfacing and general Labview experience. I am using a myRIO to control a Pittman 8222 34V Brushed DC motor (Motor Specs).
I recently created a code to control the angle of this motor using PID, which was visually implemented using the black disc with a white tick mark on it (see attached picture: "IMG_2523").
I now want to control the speed of this motor againg using PID, but I am not sure how to properly convert the encoder counts to RPM of this motor. I have attached 2 screen shots of my block diagram and my front panel for reference ("Capture" and "Capture2"). In the front panel picture, you can see my "actual" speed of the motor is a very choppy signal when it should theoretically be a flat line. To get the RPM, I currently use a shift register to store the current count value (which I converted to deg, then to radians), and then subtract the previous run's value, then divide by the while loop sampling time (10 ms). This would give me rad/s, which I then wrote a subVI to convert it to rpm.
Any help would be greatly appreciated, thanks.

Hi,
One thing you could try doing is verifying that the conversion from rad/s to rpm is working correctly.
This tutorial might also be helpful. It's not using the same hardware that you are, but goes through the general steps using PID control.
CompactRIO Motor Control Basics Tutorial: http://www.ni.com/pdf/labview/us/compactrio_motor_control_basics.pdf

SbRIO usb camera, driver from myRIO

Hi,
in myRIO the common USB camera works, is it possible to use the same set of drivers on sbRIO 9636?
I think it has the same OS, USB, only the CPU is different.
I can see the USB device, but not as an IMAQ camera.
Older posts says it was not possible, but there should be new drivers...
Thanks a lot.
Neo
Hardware-designer, inventor, freak...
FEI, VSB Technical University Ostrava

Hi NeoGHOST,
The sbRIO-9636 and myRIO are quite different under the hood. They use a different processor and OS. sbRIO-9636 is using VxWorks OS on a Power PC and myRIO uses NI Linux RT on a dual-core ARM processor.
I'm not very familiar with the USB Camera driver, but I wanted to point out that it would diffenately require a different back end implementation to support both targets.
Regards,
Spex
National Instruments
To the pessimist, the glass is half empty; to the optimist, the glass is half full; to the engineer, the glass is twice as big as it needs to be...

Myrio vs. 10DOF

Hey,
i just got my MyRio a few Days ago and i now wanted to work with a 10DOF Sensor.
10DOF Sensor Components:
- ADXL345      accelorator
- BMP085       pressure
- L3G4200D    gyro
- HMC5883L   compass
I tried to get the I2C connection work. My question is, how can i tell the Slave device the adress of the register? The I2C Vi just have the inputs "slave device" and "Bytes to write" but no "registr adress".
Sorry for my english
Simon

Hey Simon,
We discussed using the ADXL345 Accelerometer with myRIO in this thread.
In general I2C only has a slave address and data bytes. However it is common for devices to implement an instruction set that includes an internal register address pointer. The way you set this pointer will vary depending on the device and will be documented in the device data sheet. The most common way to set the device's internal address register is by writing a two bytes, a set register command and the value data byte.
Take a look at that thread and let us know if you have more questions. If you get the 10DOF working it would be great to share your code.
Thanks!
-Sam K
LabVIEW Hacker
Join / Follow the LabVIEW Hacker Group on google+

Interfacing TETRIX/NXT HiTechnic Motor controller to myRIO

I am an Adjunct instructor at a Junior College.
We are implementing the Intelitek "Advanced Engineering with myRIO" curriculum.
This is a brand new program and we have received the software, course materials
and the myRIO controller but it will be close to mid term before we get the
rest of the hardware based on the TETRIX Prime robotic platform and interface
board.
I have borrowed an older TETRIX kit from a local High School that was used with
the LEGO NXT and it hast the HiTechnic Motor controller with the NXT connector
interface.
What I am wanting to do to get the student started (we just had the 2nd week
meeting of a 14 week course) is take the motor controller with the NXT cable
and interface it to the I2C interface on the myRIO.
I had found online a German site that has a board that will directly connect
the NXT sensors to a myRIO.
I was wondering if you have any VIs that might help met get this working
quickly, even the code details from the NXT version of Labview for the Tetrix
controllers would probably help.
Thanks in advance
Scott Willis

Hi Swillis,
Unfortunately we do not have an specific library to communicate with the Tetrix controllers. The following link, contains information related to the NI LabVIEW Module for LEGO® MINDSTORMS®, but it is not supported and will not necessarily work fine for the myRIO programming.
Regards
Regards,
S.Jimenez

MyRio calculation time for RCP

Hi,
I'm a researcher in Power Electronics and I wish to know about the performance of the MyRIO.
We are currently using dSPACE (dsp1104) modules for our Rapid Control Prototyping. When we implement our control algorithm, we define a Time step in the MATLAB/Simulink environment. For example, we can not go less than 40us for a simple controller, otherwise we encounter a message of "OverRUN"
I wish to know what is the lowest Time step the MyRIO could achieve for a simple controller in a RCP loop.
thanks

Hi,
There is also not one single answer to your question since with a NI RIO platform (including NI myRIO) you have the choice to put your controller on real-time target and/or on the FPGA. NI myRIO has a 40MHz Onboard Clock putting a single FPGA tick at 25ns so also the size/complexity of your controller will define/impact the cycle time.
If your research is in power electronics you might also be interested in using the the NI Single-Board RIO General-Purpose Inverter Controller (GPIC).
Can you give me specifics about your location? I'd like to connect you to the right (technical) resource since I believe that your application/request probably deserves more then just a simple answer in this forum in order to explor all possibilities.
Regards
Ingo Foldvari
Area Sales Manager - US West Academic
National Instruments

Counter speed myrio

Hi,
I'm using a myRIO for a school project and we have to measure an quadrature encoder. There is only one problem, when we calculate how much state changes it would undergo in 1 second it's 8.400.000, so my question is, will the myRIO build-in counter be able to count that fast?
Thanks for the reply, Laseros

Hi Laseros,
If you take a look at page 23 of the MyRIO manual (http://www.ni.com/pdf/manuals/376047a.pdf ) you will find that the max frequency for Quadrature encoder input is 100kHz. If you create a "MyRIO custom FPGA project," you can actually have a look at the FPGA code that was implemented to read the encoder signal.
Best,
Jos

MyRIO simple code compilation FPGA

Hello,
I am new to FPGA and I want to compile some simple code. I know that myRIO comes with default FPGA configuration so I want to create new one and compile it. Lets say that I want blinking LED. So I create new VI on FPGA and here is simple code:
then I add it to build and start compilation
As compilation goes it says that it will use 30% of FPGA resources:
Why is that? Whole compilation on cloud server takes more than 20 minutes. I have seen some example videos on CRio FPGA and that simple code should use no more than 2% of resources and shuld compile in 2 to 3 minutes.
What I am doing wrong?
Thanks in advice

Hey Pawhan11,
There are two main reasons for the FPGA resource consumption. First is that the FPGA on the myRIO (Zynq Z-7010) is relativly small compared to some other NI targets you may have used. The second reason that even a simple FPGA application takes ~20% of the FPGA fabric is because some of the FPGA fabric is already being used for other purposes. For example some NI Real-Time targets implement UARTs, RS232 or even ethernet in the FPGA to ensure consistency between devices.
Since myRIO is based on the Xilinx Zynq chip it uses a different toolchain than previous FPGA devices which may cause the difference in compile/synth times.
-Sam K
LabVIEW Hacker
Join / Follow the LabVIEW Hacker Group on google+

Myrio tachometer implementation

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