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refsiul22
2016.01.15, 05:57 PM
Just wanted to share this info with you guys. Haven't read about it in here.
Very interesting and useful. Just download the app and measure your motors rpm.

Accuracy? I don't know yet. Please comment..

http://mini-zracer.com/forums/picture.php?albumid=181&pictureid=1748

http://mini-zracer.com/forums/picture.php?albumid=181&pictureid=1747

Jshwaa
2016.01.15, 08:37 PM
Processes audio frequency to determine speed. Neat.

Accurate? Don't see why not.

KWT
2016.01.25, 07:56 PM
I tried it and it wasn't that accurate.

byebye
2016.01.25, 08:47 PM
Need to use a photo tachometer. I have one but have yet to really use it.

Kris

Jshwaa
2016.01.31, 11:04 AM
True, photo tachometers work well because you get a definite peak and valley per rotation, however using sound should work just as good as long as there is no other audible noise being picked up by the device while the motor is running, and the audio is properly filtered to give the CPU a clean signal. Using sound to calculate speed could result in a harmonic which would create a multiplying effect to the speed calculation because the sound of the motor is creating multiple peaks and valleys per rotation. But the calculated speed should be a multiple of the actual speed, in which case the device should be able to be adjusted or calibrated to mitigate that error. Other than that, using audio should work good because the frequency of sound the motor creates is a function of how fast it is rotating. Definite linear relationship. The only other possible limiting factor is how long the device takes to calculate, but we're talking about computers running on GHz speeds. Just don't social media grandma while taching your motor. :D

Jshwaa
2016.01.31, 07:24 PM
Aw, you're no fun, Mike...

doug01n
2016.02.01, 12:06 PM
I don't think sound is a way to check RPM. Not without external calibration with a tachometer. Changing the balance or any changes in bushing or bearings may affect the sound frequency on rotation top speed. I never saw something working (enough accurately) on this way.

ilove599xx
2016.02.01, 12:40 PM
I use the cheapest smart phone like Acer,

It's hard to believe that my phone could be accruated for that kind of measurement.

Jshwaa
2016.02.02, 06:44 PM
I use the cheapest smart phone like Acer,

It's hard to believe that my phone could be accruated for that kind of measurement.

I suggest you spend the $3 and surprise yourself. Look up "FFT Plot - Real Time Sound Frequency Analyzer". This app works on the same principle, and people use variants to tune instruments.