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Old 05-05-2009, 07:58 PM
PatrickTBuckley PatrickTBuckley is offline
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Join Date: May 2009
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Default Hall effect sensor testing

Hi -

This is my first post - after reading some of the information provided on this site I am somewhat intimidated...!

My problem: I have a Ford GT40 replica that uses a Smiths Electronic speedometer....the speedo has never worked, I have substituted another speedo head and have removed the speedo and the Hall effect senor from the vehicle and set up a test bench.

I am getting 0.01 v as an output from the sensor - I suspect that this is the cause of the problem but want to make sure that I am testing the sensor correctly....

Do I have to have a pull up resister in order to test it correctly?

Thanks for your help!
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Old 05-05-2009, 08:01 PM
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bertus bertus is offline
Join Date: Apr 2008
Location: Amsterdam,Holland (GMT + 1)
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Do you have some more data on the hall sensor?

Here is a page from the EDUCYPEDIA on hall-sensors:

There are several types as you can see.
(latching, bipolair etc.)

You don't have to know everything, if you know where to find it.
When you do ask questions, you may look stupid.
When you do NOT ask questions, you will STAY stupid.

It would be nice to have the Timezone ( GMT +/- x ) in the location field in the profile.
(User CP -> Edit Your Details)
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Old 05-06-2009, 05:42 PM
premlx premlx is offline
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Yes this is likely an open collector device and would require a pull up resistor, typically limiting current to max of 20mA. Also you will need a magnet to excite the sensor into changing state. Some speed sensor use the Hall sensor as a "geartooth" sensor, in which case there is already a bias magnet behind the sensor (molded into the plastic). You can check for this with any ferrous metal. If this is the case you will need to rotate a suitable gear at a fixed gap (2-3mm, not more) away from the active face of the sensor. If there is no magnet molded into the sensor then it most likely needs a south pole of a magnet or alternating south and north poles from a "ring" magnet. most speed sensing inputs look for a uniform 50% duty cycle signal.

for more detailed info look at it should help.
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