Jump to content

As of July 17, 2015, the LabJack forums here at forums.labjack.com are shut down. New registrations, topics, and replies are disabled. All forums are in a read-only state for archive purposes.

Please visit our current forums at labjack.com/forums to view and make new posts. To post on the current forums, use your labjack.com login account. Your old LabJack forums login credentials have been retired. There are no longer separate logins for labjack.com and LabJack forums.


Photo

Dyno Project. U3 suitable?


  • Please log in to reply
6 replies to this topic

#1 EvanF

EvanF
  • Members
  • 4 posts

Posted 14 November 2010 - 04:09 PM

I'm building an inertia dyno to monitor minor performance changes on my dirt bike(s). The chassis is nearing completion and it is now time to set my mind on data acquisition solutions. It has been suggested I do the rpm calcs on board the DAQ before sending the data off to the PC as a PC would not be fast enough to compute the incoming data. I am not sure if the U3 is capable of doing this. If it can't my question is: Will the U3 and bundled software provide me with a torque reading solution. Here are the details of my dyno. 150kg drum with a max rotation spd of 22revs per second. A 24slot interrupter will be used to count the rotations (please view attached pic and advise if suitable as an interrupter) 22x24=528 pulses a second. Engine 12000RPM max. Thanks in advance. Attached File  labjack.rar   282.26KB   692 downloads

#2 LabJack Support

LabJack Support
  • Admin
  • 8677 posts

Posted 15 November 2010 - 02:15 PM

Sounds like no problem. I would use a timer on the U3 in 32-bit period measurement mode:

http://labjack.com/s...s-guide/2.9.1.3

Every time the terminal detects a rising edge, it will note the time since the previous rising edge and store this in the register for that timer. The question then is how often you need to read this register? That is, how often do you want to update your frequency reading?


Here is a good forum topic about frequency measurement:

https://forums.labja...?showtopic=1105

#3 EvanF

EvanF
  • Members
  • 4 posts

Posted 15 November 2010 - 03:53 PM

Sounds like no problem. I would use a timer on the U3 in 32-bit period measurement mode:

http://labjack.com/s...s-guide/2.9.1.3

Every time the terminal detects a rising edge, it will note the time since the previous rising edge and store this in the register for that timer. The question then is how often you need to read this register? That is, how often do you want to update your frequency reading?


Hi,
I just had a quick look at "2.9.1.3 - Period Measurement (32-Bit, Modes 2 & 3)"
My first thought is, I would need to time both engine revolutions and drum revolutions. Is the U3 capable of handling both without errors or is it only capable of one routine?

In this 32-bit mode, the processor must jump to an interrupt service routine to record the time, so small errors can occur if another
interrupt is already in progress. The possible error sources are:...



I haven't given thought to how often the updates would need to be. It would be written to a torque and horsepower graph over a 10 second duration.

#4 LabJack Support

LabJack Support
  • Admin
  • 8677 posts

Posted 15 November 2010 - 04:35 PM

The U3 has 2 timers, so it can do 2 period measurements and you should be good. I gather the max engine signal frequency will be 24*12000/60 = 4800 Hz? That would be fine.

Up to about 100 readings/second you can use command/response mode. To go faster you need to use stream mode.

http://labjack.com/s...3/users-guide/3

If you don't want to develop your own software, you should be able to do this with LJLogUD, LJStreamUD, or DAQFactory.

#5 EvanF

EvanF
  • Members
  • 4 posts

Posted 15 November 2010 - 04:52 PM

The U3 has 2 timers, so it can do 2 period measurements and you should be good. I gather the max engine signal frequency will be 24*12000/60 = 4800 Hz? That would be fine.

Up to about 100 readings/second you can use command/response mode. To go faster you need to use stream mode.

http://labjack.com/s...3/users-guide/3

If you don't want to develop your own software, you should be able to do this with LJLogUD, LJStreamUD, or DAQFactory.


Engine frequency would be 12000/60 = 200Hz and grabbed with an inductive pick up. That in itself will be a problem to ensure the signal is clean.

I am not a software developer so yes I was thinking DAQFactory..yet another learning curve...hopefully not too steep!

Aus and Nz don't appear to have stock in hand of the U3 so I may have to order online.

#6 LabJack Support

LabJack Support
  • Admin
  • 8677 posts

Posted 16 November 2010 - 11:45 AM

Traditionally you would use script in DAQFactory to enable and configure the timers. Then you just read the timers the normal DAQFactory way.

An alternative, though, is to get the latest LJControlPanel, UD driver, and U3 firmware, and then configure the timers as power-up defaults.

I tested with LJCP V2.24, UD driver V3.22, and U3 firmware V1.33. If you don't have those versions or higher, see "Getting The Latest ..." here:

http://labjack.com/support/u3

In LJCP go to "Config Defaults" and set PinOffset = 4, # Timers = 2, TimerClockBase = 1 MHz/Divisor, TimerClockDivisor = 1, Timer0 & Timer1 Mode = RisingEdges32. Then click "Write Values". Close LJCP and power-cycle the U3 to load the new power-up defaults.

Then you can use LJStreamUD:

http://labjack.com/s...t/ud/ljstreamud

Set # Channels to 4 and set the first 4 channels to 200, 224, 201, and 224:

http://labjack.com/s...ers-guide/3.2.1

If you need more flexibility than you get from LJStreamUD, you can move on to DAQFactory.

#7 TonyF

TonyF
  • Members
  • 16 posts

Posted 13 September 2013 - 01:14 AM

EvanF,

 

Did you get this up and running.  I am developing a similar device but will be writing my own software.  I'd be interested in hearing more of your experiences.




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users