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

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Current Stable:
1994 S500 v140, 210k miles, white with grey.

Former Mercedes in the Stable:
1983 300CD Turbo diesel 515k mi sold (rumor has it, that it has 750k miles on it now)
1984 300CD Turbo Diesel 150 k mi sold
1982 300D Turbo Diesel 225 sold
1987 300D Turbo Diesel 255k mi sold
1988 300 CE AMG Hammer 15k mi sold
1986 "300E" Amg Hammer 88k mi sold (it was really a 200, not even an E (124.020)
1992 500E 156k mi sold
etc.

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

pic

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__________________
Current Stable:
1994 S500 v140, 210k miles, white with grey.

Former Mercedes in the Stable:
1983 300CD Turbo diesel 515k mi sold (rumor has it, that it has 750k miles on it now)
1984 300CD Turbo Diesel 150 k mi sold
1982 300D Turbo Diesel 225 sold
1987 300D Turbo Diesel 255k mi sold
1988 300 CE AMG Hammer 15k mi sold
1986 "300E" Amg Hammer 88k mi sold (it was really a 200, not even an E (124.020)
1992 500E 156k mi sold
etc.

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

Attached Thumbnails

 

__________________
Current Stable:
1994 S500 v140, 210k miles, white with grey.

Former Mercedes in the Stable:
1983 300CD Turbo diesel 515k mi sold (rumor has it, that it has 750k miles on it now)
1984 300CD Turbo Diesel 150 k mi sold
1982 300D Turbo Diesel 225 sold
1987 300D Turbo Diesel 255k mi sold
1988 300 CE AMG Hammer 15k mi sold
1986 "300E" Amg Hammer 88k mi sold (it was really a 200, not even an E (124.020)
1992 500E 156k mi sold
etc.

hall

Attached Thumbnails

 

__________________
Current Stable:
1994 S500 v140, 210k miles, white with grey.

Former Mercedes in the Stable:
1983 300CD Turbo diesel 515k mi sold (rumor has it, that it has 750k miles on it now)
1984 300CD Turbo Diesel 150 k mi sold
1982 300D Turbo Diesel 225 sold
1987 300D Turbo Diesel 255k mi sold
1988 300 CE AMG Hammer 15k mi sold
1986 "300E" Amg Hammer 88k mi sold (it was really a 200, not even an E (124.020)
1992 500E 156k mi sold
etc.

hall

Attached Thumbnails

 

__________________
Current Stable:
1994 S500 v140, 210k miles, white with grey.

Former Mercedes in the Stable:
1983 300CD Turbo diesel 515k mi sold (rumor has it, that it has 750k miles on it now)
1984 300CD Turbo Diesel 150 k mi sold
1982 300D Turbo Diesel 225 sold
1987 300D Turbo Diesel 255k mi sold
1988 300 CE AMG Hammer 15k mi sold
1986 "300E" Amg Hammer 88k mi sold (it was really a 200, not even an E (124.020)
1992 500E 156k mi sold
etc.

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.

Attached Thumbnails

 

__________________
Current Stable:
1994 S500 v140, 210k miles, white with grey.

Former Mercedes in the Stable:
1983 300CD Turbo diesel 515k mi sold (rumor has it, that it has 750k miles on it now)
1984 300CD Turbo Diesel 150 k mi sold
1982 300D Turbo Diesel 225 sold
1987 300D Turbo Diesel 255k mi sold
1988 300 CE AMG Hammer 15k mi sold
1986 "300E" Amg Hammer 88k mi sold (it was really a 200, not even an E (124.020)
1992 500E 156k mi sold
etc.

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

__________________
'87 MBenz 190E 2,3 8vlv

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

__________________
2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)

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.

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MERCEDES Benz Master Guild Technician (6 TIMES)
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