Electronics > Beginners
How to measure RPM of DC fan?
(1/3) > >>
shai:
I have a fan that is 30x30mm diameter and the hub is about 16mm diameter (when looking from the top). I read that you can use a Tachometer, but after searching for those on Amazon, I see that you need to apply tape to the object you're measuring RPM of and I'm not sure if there's enough space for the tape size required. Is there a better way to measure a small DC fan's RPM? My fan only has 12v/GND leads, no yellow wire for hall effect sensor. Any help appreciated!

Reason for this is because I tore out a regular 30x30x10 fan's DC "magnetic motor" and fitting my own bearing on it for a custom fan. So I want to swap bearings and see how they affect RPM. (but this is a separate topic  :))
ogden:
In case you have oscilloscope, you need straight core (thru-hole vertical) inductor. No need to glue magnet to rotor, because fan have built-in one :)

http://paulorenato.com/index.php/electronics-diy/113-measuring-rpm-with-an-oscilloscope

Other way of measuring: flashlight+photodiode+scope. Note that LED can be used as photodiode as well.


David Hess:
The DC ripple current can also be used to measure the RPM of a DC brushless fan.  Areca uses this trick on their RAID controllers to monitor the cooling fan RPM.  Small expansion card sized fans with a tachometer output are not common.
Sudo_apt-get_install_yum:
Couldn’t you use the current draw of the motor to get some sort of indication of the motor speed? Higher load = higher current draw, since you know the voltage and the max RPM for that voltage.
I don’t know how accurate this is but for rough estimation it should be fine!
ogden:

--- Quote from: Sudo_apt-get_install_yum on November 26, 2018, 11:23:41 am ---Couldn’t you use the current draw of the motor to get some sort of indication of the motor speed? Higher load = higher current draw, since you know the voltage and the max RPM for that voltage.
I don’t know how accurate this is but for rough estimation it should be fine!

--- End quote ---

Waste of time. Low friction bearings can lead to faster RPM, yet lower consumption. Even audio spectrum application for mobile phone is way better tool. This looks good
Navigation
Message Index
Next page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod