Hall Effect Sensor- how does it work?
 

In my University Physics II class (Electricity and magnetism) we are studying magnetism currently, and the instructor started to go over the "hall effect." I know that mercedes have a hall effect sensor on the back of the spedometer to regulate the cruise control. So I asked him after class if he knew how it worked or anything and he didnt. I was wondering if anyone here thats Electrically inclined knows how it works. He said if I bring in a spedometer he can figure it out, but I want to know, then I can share to the class that we are studying things that actually relate to real everyday life and maybe I can get some bonus points.

I have a spedometer from a w123 1982 300d that I took apart, so I can post pictures or anything anyone needs to help me explain. Thanks, Austin

I believe the Hall effect happens inside the transmission. A rotor (with three arms, I think) on the output shaft spins near a pickup coil which generates a signal for the speedometer (in 560 SL/SEL/SECs, anyway).

All you see on the back of the speedo is four male electrical connectors (12v+, ground, signal FROM the trans, and signal TO the cruise control).

Another device that uses the same principle is the Pertronix ignition (which replaces mechanical points). A rotor with small magnets along the periphery replaces the stock rotor, and each time a magnet goes by the pickup, a small electrical current is created.

Think of the Hall effect in these applications as a small pulsed example of the phenomenon that makes a generator generate DC current.

M D "Doc" Nugent

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the black part is the hall effect sensor, and the bronze piece is for the speedometer cable.

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close up of the hall effect sensor, the bronze colored tab goes into and rides on the circular disc which is turned by the spedometer cable, then it has some coils on the inside. maybe this will clear up what I am talking about. Thanks for your help.

I gave you a fiver!
 

Damn! Good thread, omegabenz! I really like when people actually share stuff like this on the forums.

Hope you figured out about the hall effect...Now it's my turn :D

I believe Hall effect sensors are also used in EXPRESS (ie "One-Touch Up/Dn) Windows.

The W201 (190E) uses a hall effect but the pictures that are posted are on an INDUCTIVE style pick-up.
Hall effect is an on/off signal needing a voltage supply while the inductive(pictured) supplies A/C voltage.