Outrunner mag tach?

[jrb]

Hoping someone has done something simple for this.

How about a magnetic sensor tacho that counts pulses from the shell of an outrunner.

From many tools we know about what the rpm should be so a simple interger calc number of poles should work fine.

TIA,


Jim

[mcross]

I use a hall sensor that I read with a frequency meter. Frequency divided by pole pairs times 60 will give the RPM.

Works great as long as there's enough flux "leaking".

[Tomapowa]

Here's a DIY solution that taps onto one of the brushless wires:
http://www.rcgroups.com/forums/showthread.php?t=1006124&highlight=rpm

Eagle Tree and Medusa Research make RPM sensors too that work similarly by detecting these pulses.

Not too sure on the reliability of hall effect sensors detecting motor EMF, especially from outside the outrunner as magnets/can could shield alot of the EMF.

[jrb]

Thanks for the info; hope others with interest post too.

[mcross]

The hall has to be placed to sense the magnets.