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Unread 14-02-2011, 21:17
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Re: Light sensor as shaft encoder too fast for Lab View Code?

Quote:
Originally Posted by Speeder View Post
Try putting an indicator (numeric), either in your .vi or on the dashboard. Watch the indicator to see it count up/down. You'll probably see the sensor is working fine. There is a tremendous lag between the cRio and the Classmate display. The LED cannot possibly display accurately anything other than a very slow pulse but the numeric indicator, when the screen refreshes, will show actual counts.

Don
Your information is inaccurate.

The led shows the information that it can process.
depending on the loop rate(usually maximum 100hz) you can only measure up to 50Hz which is 300rpm.
Anything faster will have to be done using the counter vi's as noted before.

Counter vi's direct the fpga to count the number of pulses. The fpga can count as fast as 50 MHz(this is not exact, but it is much much much faster than the processor without using an interrupt).
Then the processor can ask teh fpga for the count every loop and get a number back and act upon that number 100 times a second.
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