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Topic: hall effect sensor and brushed small dc motor (Read 1 time) previous topic - next topic


Hi guys !
Thanks for reading this post:

I have this sensor from sparkfun: https://www.sparkfun.com/products/9312
it is a latched hall effect sensor.

I'm trying to build a dc motor tachometer, and to prototype it i have connected
5v, gnd and 10k pullup at the output.
I'm looking at the output with an oscilloscope.

If i move a small speaker to the hall sensor, it changes its state depending on the polarity of the speaker's magnet.
But if i put my hall sensor next to a small dc motor (parallel to the shaft) (such as this: http://www.solarbotics.com/product/tpm2/ , or even this : http://www.robotmarketplace.com/products/0-PL1596.html)

I expect to see more or less a square wave pattern on the oscilloscope, but i dont. My motor spins like crazy (~10,000 rpm) but no effect on the hall sensor.  (stays flat)

Any ideas ?

thanks in advance A.

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