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Topic: hall effect sensor as a rpm mesauerment device (Read 10 times) previous topic - next topic

red65536

hello.  i had a quick question about hall effect sensors and arduino sample rates.  i want to use a hall effect sensor to measure the rpm and acceleration of a wheel.  the wheel will accelerate to 6000 rpm, or 100 rev a sec in about 6 seconds or so.  my question is about the speed of the digital input.  

first, will there be a race condition, and inaccuracy from the sensor and the clock pulses not syncing up.

and two, if anyone has a recommendation for a decent hall effect sensor.


i was also considering a optical sensor, but the set up the hall effect and magnet set up would work better i think.

thanks for the help,

anthony
anicolai@coe.neu.edu

mrmeval

http://www.arduino.cc/playground/Main/ReadingRPM

Fans run at 3000rpms and this seems to work fine. ;)
I'm not sure how the fans get the hall effect sensor to output +5v pulses so you may want to look at an hall effect sensor that has the circuitry to do that for you.

If it was designed by man it can be repaired by man.

Cheater

100 times per second? Thats nothing. :)
16Mhz / 100hz gives quite a few instructions between revolutions.

You'd probably be able to accurately detect the RPM and output it on a LCD without any problems.

red65536

how would you poll the sensor so theres is a constant sample rate, would it be by using an interupt, i feel that the code delay times would fluctuate based on the data that is acquired and the different times it will take to pass it along the serial conenction.

Cheater

You get a couple of hundred instructions between each pulse so depending on your application its fine.

Alternatively just make it drive a interrupt and use it to increment a counter.
Probably simplest that way.

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