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  #1  
Old 05-05-2009, 07:58 PM
PatrickTBuckley PatrickTBuckley is offline
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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
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Hello,

Do you have some more data on the hall sensor?

Here is a page from the EDUCYPEDIA on hall-sensors:
http://www.educypedia.be/electronics/sensorshall.htm

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

Greetings,
Bertus
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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 http://www.melexis.com/Assets/Hall_A...ide__3715.aspx it should help.
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