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Weak Magnetic Field Sensing

C

Christopher

Jan 1, 1970
0
Hello Everyone,


Weak Magnetic Field Sensing

Before I begin to chase the madness into the evening, I would like to
know if using a magnetic sensor like the Hall Effect would allow me to
convert "a small magnetic rod's distance into resistance. " The few
circuits sensing magnetism I see seem to be more of a window
comparator behavior or 0/1 or a tripped on state.

Ideal: is a strong "hand held" magnet moving 8" to 1" from the sensor,
this would create a resistance change of 10k down to 1k or something
to that effect not necessarily that resistance change.

Question: Is this conversion possible or unreasonable?

Thank you for any input or humor,

* * *
Christopher

Temecula CA.USA
http://www.oldtemecula.com
 
P

Pieter

Jan 1, 1970
0
Hello Everyone,
Weak Magnetic Field Sensing
Before I begin to chase the madness into the evening, I would like to
know if using a magnetic sensor like the Hall Effect would allow me to
convert "a small magnetic rod's distance into resistance. " The few
circuits sensing magnetism I see seem to be more of a window
comparator behavior or 0/1 or a tripped on state.

Ideal: is a strong "hand held" magnet moving 8" to 1" from the sensor,
this would create a resistance change of 10k down to 1k or something
to that effect not necessarily that resistance change.

Question: Is this conversion possible or unreasonable?

Thank you for any input or humor,
Christopher
Temecula CA.USA
http://www.oldtemecula.com

Hi christopher,

With a Hall sensor you can measure distances. Here is a 2 ways to do
this with high precision:

(1a) To measure a distance to a non-magnetized but magnetizable metal
like iron etc:
Mount a strong magnet on top of the sensor and move the object to
meaure to measure to and from this sensor-magnet combination.

or

(1b) To measure the distance to a magnet:
Only use the sensor, nothing else mounted. Here you may use a sensor
that is more sensitive, all depends on the distances and magnetic
fields you want to measure.

then measure it:

(2) Measuring the magnetic field:
It must be a sensor that can handle larger fields like the Infineon
KSY10, KSY13, KSY14, KSY44 (we sell those) or other ones. Let a
current of 5 mA run through the inputs (you can also do it with a
voltage, but a current gives more linearity and better temparature
behaviour, all depends on how precise it must be). You can now measure
the resulting magnetic field that is influenced by the distance. With
a strong magnet, the output will get something like 100 to 250 mV at a
very small distance and very low at a large distance.

Feel free to ask me any questions at: [email protected] (without
the NOSPAM)

Pieter Hoeben
 
B

Boris Mohar

Jan 1, 1970
0
Hello Everyone,


Weak Magnetic Field Sensing

Before I begin to chase the madness into the evening, I would like to
know if using a magnetic sensor like the Hall Effect would allow me to
convert "a small magnetic rod's distance into resistance. " The few
circuits sensing magnetism I see seem to be more of a window
comparator behavior or 0/1 or a tripped on state.

Ideal: is a strong "hand held" magnet moving 8" to 1" from the sensor,
this would create a resistance change of 10k down to 1k or something
to that effect not necessarily that resistance change.

Question: Is this conversion possible or unreasonable?

Thank you for any input or humor,

* * *
Christopher

Temecula CA.USA
http://www.oldtemecula.com


I am not sure how far will these go

http://home.nve.com/
http://home.nve.com/Downloads/analog_catalog.pdf




Regards,

Boris Mohar

Got Knock? - see:
Viatrack Printed Circuit Designs (among other things) http://www.viatrack.ca

void _-void-_ in the obvious place
 
J

John Larkin

Jan 1, 1970
0
Hello Everyone,


Weak Magnetic Field Sensing

Before I begin to chase the madness into the evening, I would like to
know if using a magnetic sensor like the Hall Effect would allow me to
convert "a small magnetic rod's distance into resistance. " The few
circuits sensing magnetism I see seem to be more of a window
comparator behavior or 0/1 or a tripped on state.

Ideal: is a strong "hand held" magnet moving 8" to 1" from the sensor,
this would create a resistance change of 10k down to 1k or something
to that effect not necessarily that resistance change.

Question: Is this conversion possible or unreasonable?

Thank you for any input or humor,

* * *
Christopher

Temecula CA.USA
http://www.oldtemecula.com

Keep in mind that once you get into the far-field region (ie, farther
from the magnet than a few times its length) the field strength will
drop off with the cube of distance, which is pretty severe.

I'd guess that it will be difficult for a Hall sensor to give you much
signal 8" away from a "small" magnet. You might try it with a compass
first to get a feel for magnitudes.

John
 
R

Rene Tschaggelar

Jan 1, 1970
0
Christopher said:
Hello Everyone,


Weak Magnetic Field Sensing

Before I begin to chase the madness into the evening, I would like to
know if using a magnetic sensor like the Hall Effect would allow me to
convert "a small magnetic rod's distance into resistance. " The few
circuits sensing magnetism I see seem to be more of a window
comparator behavior or 0/1 or a tripped on state.

Ideal: is a strong "hand held" magnet moving 8" to 1" from the sensor,
this would create a resistance change of 10k down to 1k or something
to that effect not necessarily that resistance change.

Question: Is this conversion possible or unreasonable?

Thank you for any input or humor,

By AC excitation, the sensitivity of a Hall element
can be enhanced by a few orders of magnitude.
Lookup the term "lock-in amplifier".

Rene
 
F

Fred Bloggs

Jan 1, 1970
0
Christopher said:
Hello Everyone,


Weak Magnetic Field Sensing

Before I begin to chase the madness into the evening, I would like to
know if using a magnetic sensor like the Hall Effect would allow me to
convert "a small magnetic rod's distance into resistance. " The few
circuits sensing magnetism I see seem to be more of a window
comparator behavior or 0/1 or a tripped on state.

Ideal: is a strong "hand held" magnet moving 8" to 1" from the sensor,
this would create a resistance change of 10k down to 1k or something
to that effect not necessarily that resistance change.

Question: Is this conversion possible or unreasonable?

Yes- but you will want to use a sensor + PIC/STAMP/uProc combination for
calibration and linearization. Analog is largely a joke in applications
like this.
 
C

Christopher

Jan 1, 1970
0
Hello Everyone,

The mean ones have not chewed me out yet so what exactly am I trying
to accomplish?

Finding the best method using any type of sensor or effect for a
non-tactile, hand controlled volume attenuating circuit. I just need
to know what sensor would work best, I will design the support
circuit.

Ken Smith !!! I do have a "cow magnet" which is chrome and
about the size of my little finger, how did you ever guess that one? I
only learned of these this week.
***********************
Explanation:

I am attempting to turn my "hand" into a human potentiometer with at
least an 8" sweep range. I thought holding a magnet could give me a
usable effect or force to do this.

I want to explore a new volume control method of a special musical
instrument called a "Theremin". The normal theremin volume method uses
a antenna and detects the shift in frequency of two perfectly balanced
oscillators. It has very wide physical sensing area of more than one a
foot diameter. Placing my hand out 12" then moving it next to the
control antenna quiets the volume without touching it.

Yes, I can do the above technique, along with an optical method and a
mechanical balance of two magnets opposing one another method which
works but is not responsive enough and is sloppy.

I want to use a different approach that will have a working width in
free space of about a 4" to 6" diameter and have detectable downward
sweep range starting at least 8" to the outside, then have a
controlled measurable output as my hand magnet moves down to the
control sensor pickup.

This will allow me to have more than one (maybe four) sensor/detector
spread out in the original one foot diameter or musical volume control
panel area of which my hand approaches.

Non of the above values or measurements are critical and could be
modified to adapt to the approach.


I have a webpage I show hobbyists/musicians how to build my theremin
design and this volume control method would be a great enhancement.

http://www.oldtemecula.com/theremin/


"The theremin is the only musical instrument played without touching
anything." It has can sound like a musical saw or an angels voice.

This is Clara Rockmore Circa 1940 .mp3 777kb
http://www.oldtemecula.com/theremin/sounds/cr-rachmaninoff_vocalise.mp3


Thank you, your ideas are greatly appreciated.


* * *
Christopher

Temecula CA.USA
http://www.oldtemecula.com
 
K

Ken Smith

Jan 1, 1970
0
Christopher said:
Ken Smith !!! I do have a "cow magnet" which is chrome and
about the size of my little finger, how did you ever guess that one? I
only learned of these this week.

My spies are everywhere.

BTW: Either you've got a big little finger or a small cow magnet there.
 
R

Robert Baer

Jan 1, 1970
0
Christopher said:
Hello Everyone,

The mean ones have not chewed me out yet so what exactly am I trying
to accomplish?

Finding the best method using any type of sensor or effect for a
non-tactile, hand controlled volume attenuating circuit. I just need
to know what sensor would work best, I will design the support
circuit.

Ken Smith !!! I do have a "cow magnet" which is chrome and
about the size of my little finger, how did you ever guess that one? I
only learned of these this week.
***********


************
Explanation:

I am attempting to turn my "hand" into a human potentiometer with at
least an 8" sweep range. I thought holding a magnet could give me a
usable effect or force to do this.

I want to explore a new volume control method of a special musical
instrument called a "Theremin". The normal theremin volume method uses
a antenna and detects the shift in frequency of two perfectly balanced
oscillators. It has very wide physical sensing area of more than one a
foot diameter. Placing my hand out 12" then moving it next to the
control antenna quiets the volume without touching it.

Yes, I can do the above technique, along with an optical method and a
mechanical balance of two magnets opposing one another method which
works but is not responsive enough and is sloppy.

I want to use a different approach that will have a working width in
free space of about a 4" to 6" diameter and have detectable downward
sweep range starting at least 8" to the outside, then have a
controlled measurable output as my hand magnet moves down to the
control sensor pickup.

This will allow me to have more than one (maybe four) sensor/detector
spread out in the original one foot diameter or musical volume control
panel area of which my hand approaches.

Non of the above values or measurements are critical and could be
modified to adapt to the approach.


I have a webpage I show hobbyists/musicians how to build my theremin
design and this volume control method would be a great enhancement.

http://www.oldtemecula.com/theremin/


"The theremin is the only musical instrument played without touching
anything." It has can sound like a musical saw or an angels voice.

This is Clara Rockmore Circa 1940 .mp3 777kb
http://www.oldtemecula.com/theremin/sounds/cr-rachmaninoff_vocalise.mp3


Thank you, your ideas are greatly appreciated.


* * *
Christopher

Temecula CA.USA
http://www.oldtemecula.com
*THANK YOU* very much for disclosing thje file size!!!!!
 
M

martin griffith

Jan 1, 1970
0
Hello Everyone,

The mean ones have not chewed me out yet so what exactly am I trying
to accomplish?

Finding the best method using any type of sensor or effect for a
non-tactile, hand controlled volume attenuating circuit. I just need
to know what sensor would work best, I will design the support
circuit.
snip
Did this 10 years ago with a friend, using ultrasonics
http://www.walterfabeck.com/chromasone.htm


martin
 
P

Pieter

Jan 1, 1970
0
Keep in mind that once you get into the far-field region (ie, farther
from the magnet than a few times its length) the field strength will
drop off with the cube of distance, which is pretty severe.

I'd guess that it will be difficult for a Hall sensor to give you much
signal 8" away from a "small" magnet. You might try it with a compass
first to get a feel for magnitudes.

At 8" you need a sensitive sensor. But that may saturate at 1".

Pieter
 
R

Rich Grise

Jan 1, 1970
0
Finding the best method using any type of sensor or effect for a
non-tactile, hand controlled volume attenuating circuit. I just need
to know what sensor would work best, I will design the support
circuit. ....
I am attempting to turn my "hand" into a human potentiometer with at
least an 8" sweep range. I thought holding a magnet could give me a
usable effect or force to do this.

Use LDRs (or PHDs or PHTs) and make a lumemin. A google search says
"Popular Electronics, April 1955", but the link is dead. )-; Maybe
someone has a copy of that issue. (yeah, right!) ;-)

You can still use your bare hands, and there's no RF.

Good Luck!
Rich
 
P

Paul Burke

Jan 1, 1970
0
Honeywell do a magnetoresistive sensor that has 2 bridges at 90 degrees,
so it should be easy to make it sense a magnet waved around.

Paul Burke
 
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