Badcaps.net Forum
Go Back   Badcaps Forums > Troubleshooting Hardware & Devices and Electronics Theory > General Electronics Technical Discussion
Register FAQ Calendar Search Today's Posts Mark Forums Read

 
Thread Tools Display Modes
Old 02-07-2021, 02:57 AM   #1
debugtimog
Member
 
Join Date: Jul 2018
City & State: Kedah
My Country: Malaysia
I'm a: Knowledge Seeker
Posts: 30
Default Magneto-resistor Digital Output Potentiometer

Hello,

I am looking for a replacement for a Magneto-resistor type potentiometer model SMP-1504 by manufacturer SAKAE TSUSHIN KOGYO CO., LTD. I have already contacted them but they no longer manufacture this type. potentio pic.JPG
What the manufacturer have are inductive types which they say is analog output and is not compatible with the Magneto-resistor type which is digital output. I am not sure why is it not compatible that but I did test it with according to specs input voltage of 5vdc and its out of 1.5v min and 4.5v max is according to specs also.
min max graph.JPG
datasheet.JPG
The potentiometer turn together when the DC motor turns through a belt.motor_potentio.JPG
The input of the potentiometer is from a 5vdc reference voltage and the output is into an OpAmp as indicated in the red arrow. schem.JPG
Please help me analyze and suggest a replacement for this. Many thanks to all of you.
debugtimog is offline   Reply With Quote
Old 02-07-2021, 04:53 AM   #2
stj
Great Sage 齊天大聖
 
stj's Avatar
 
Join Date: Dec 2009
City & State: Europe
My Country: some shithole run by Israeli agents
I'm a: Professional Tech
Posts: 24,386
Default Re: Magneto-resistor Digital Output Potentiometer

interesting devices.

so do you have a faulty one?
and what do you need, a digital output?
how does that work? binary? pulses?
stj is offline   Reply With Quote
Old 02-07-2021, 10:49 PM   #3
debugtimog
Member
 
Join Date: Jul 2018
City & State: Kedah
My Country: Malaysia
I'm a: Knowledge Seeker
Posts: 30
Default Re: Magneto-resistor Digital Output Potentiometer

Hi STJ,

I do have a good one in which i tried to run a DC inout voltage, I notice that the PSU that I am using did not indicate a current at any time while i was rotating the potentiometer. When it drop to min 1.5vdc to 4.5vdc there was no currrent draw. I then though that maybe that was the OEM was talking about that this one has digital output, while if he would provide me with their latest one that is inductive contactless potentiometer which is analog output there would be a current draw and my opamps would have a different response. I am not sure also.

Here is the link from which i tried to study also:
https://eepower.com/resistor-guide/r...eto-resistor/#

Magneto resistor
Chapter 3 - Resistor types
What is a magneto resistor
Magneto resistors have a variable resistance which is dependent on the magnetic field strength. A Magneto resistor can be used to measure magnetic field presence, strength and direction. They are also known as magnetic dependent resistors (MDR). A magneto resistor is a subfamily of magnetic field sensors or magnetometers.

Magneto resistor definition
A magneto resistor is a resistor of which the electrical resistance changes when an external magnetic field is applied.
Magneto resistor characteristics
Magneto resistors make use of the magnetoresistance effect. This effect was first discovered in 1856 by William Thomson, also known as Lord Kelvin. The effect is noticed in ferromagnetic materials and dependent on the magnetic field strength and angle between the direction of electric current and the magnetic field. This effect is therefore known as anisotropic magnetoresistance (AMR). Other, more recently discovered magnetoresistance effects are the giant magnetoresistance effect (GMR), collosal magnetoresistance effect (CMR) and tunnel magnetoresistance effect (TMR). Because most conventional magneto resistors utilize the AMR effect, the other effects will not be discussed in this article.

Permalloy, an alloy consisting of 81% nickel (Ni) and 19% iron (Fe) has a high anisotropic magneto resistance as well as a low magnetostriction (change in size due to magnetic fields) and therefore is a favorite material for magneto resistors.

Magneto resistors are often constructed of long thin films of permalloy. To increase the sensitivity of a permalloy magneto resistor, shorting bars of aluminium or gold are placed on the thin permallow films under an angle of 45 degrees. This forces the current to flow in a direction of 45 degrees relative to the length of the film. This is called a barber pole configuration.
barber pole.JPG
Visualization of the barber pattern used in magneto resistorsPermalloy fim magnetoresistor using barber pole pattern of shorting bars

a typical AMR magnetoresistive sensor is constructed of a combination of 4 permalloy thin film magnetoresistors, connected in a wheatstone measurement bridge.

Magneto resistor applications
Various applications are possible as magnetic field sensing devices, applications include for example:

Electronic compass
Magnetometry, measurement of magnetic field intensity and direction
Position sensors
Angle position sensors
Rotary postion sensors
Linear posistion sensors
Ferrous metal detection
vehicle and traffic detection
Magneto resistor symbol
The following symbol is used for a magneto resistor. It is shown as a variable resistor which is dependent on magnetic flux, indicated by 'x'.

magneto resistor symbolMagneto resistor symbolIEC standard
debugtimog is offline   Reply With Quote
Old 02-08-2021, 12:09 AM   #4
redwire
Badcaps Veteran
 
Join Date: Dec 2010
City & State: Alberta
My Country: Canada
Posts: 1,993
Default Re: Magneto-resistor Digital Output Potentiometer

Wow, life rated 100,000,000 shaft rotations. The original is an analog angle sensor, +-45 degrees (sine).
Since the sensor is Japanese, it's likely all the parts are custom from Japan.
If the sensor is dead and does not work, I would take it apart.
You could buy a new raw MR sensor. Just have to match the magnet strength and package.

MR sensors just ignore digital/switch type sensors.
Many manufacturers of them:
Allegro Hall Sensors
Infineon
Honeywell, NXP as well.
redwire is offline   Reply With Quote
Old 02-09-2021, 06:35 AM   #5
sam_sam_sam
Badcaps Veteran
 
Join Date: Jul 2011
City & State: Sunny Jacksonville FL
My Country: USA
Line Voltage: 120 Volts 60 HZ
I'm a: Knowledge Seeker
Posts: 2,601
Default Re: Magneto-resistor Digital Output Potentiometer

I was wondering what else you would use this in so I went to the website link to read about what it is and saw this ( vehicle and traffic detection ) I have some experience with this when I work at a facility that had this system

Thanks for posting the information
__________________
9 PC LCD Monitor
6 LCD Flat Screen TV
30 Desk Top Switching Power Supply
10 Battery Charger Switching Power Supply for Power Tool
6 18v Lithium Battery Power Boards for Tool Battery Packs
1 XBox 360 Switching Power Supply and M Board
25 Servo Drives 220/460 3 Phase
6 De-soldering Station Switching Power Supply 1 Power Supply
1 Dell Mother Board
15 Computer Power Supply
1 HP Printer Supply & Control Board * lighting finished it *


These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
2 Hem Saw Computer Stack Board

All of these had CAPs POOF
All of the mosfet that are taken out by bad caps

Last edited by sam_sam_sam; 02-09-2021 at 06:53 AM..
sam_sam_sam is offline   Reply With Quote
Old 02-09-2021, 11:44 AM   #6
R_J
Badcaps Veteran
 
Join Date: Jun 2012
City & State: ☻
My Country: Canada
I'm a: Professional Tech
Posts: 6,979
Default Re: Magneto-resistor Digital Output Potentiometer

Is this similar? these are called a "Hall effect potentiometer" Throttle Position Sensor in Hall Effect Technology
Attached Files
File Type: pdf 981he.pdf (167.3 KB, 3 views)

Last edited by R_J; 02-09-2021 at 11:48 AM..
R_J is offline   Reply With Quote
Old 02-09-2021, 11:40 PM   #7
debugtimog
Member
 
Join Date: Jul 2018
City & State: Kedah
My Country: Malaysia
I'm a: Knowledge Seeker
Posts: 30
Default Re: Magneto-resistor Digital Output Potentiometer

I found below comparison, Im still not sure if i can use the "hall effect" as replacement.

Magnetoresistive Sensors 279 and Hall Effect Sensors 73 are both commonly used to detect magnetic field strength. Both technologies are compatible with integrated circuit processing. So is there any difference between them when designing a sensor application?

In general, Magnetoresistive sensors have much higher sensitivity than Hall Effect sensors. A magnetoresistive device’s sensitivity is adjustable through the selection of film thickness and line width, allowing you to tune the part to your needs.

In sensor application, magnetoresistive sensors are omni-polar (operates with North and South pole), while Hall Effect is beneficial for highly linear measurements with no saturation effects out to extremely high field strength.
debugtimog is offline   Reply With Quote
Old 02-10-2021, 02:31 PM   #8
budm
Badcaps Veteran
 
budm's Avatar
 
Join Date: Feb 2010
City & State: S.F. Bay area
My Country: USA
Line Voltage: 120V 60Hz
I'm a: Knowledge Seeker
Posts: 39,116
Default Re: Magneto-resistor Digital Output Potentiometer

I look at the schematic, the input of the circuit is for interfacing with the analog output of the sensor.
What is wrong with the old sensor?
Do you have high res or PDF of the schematic?
What is this unit you are working on? Make and model?
__________________
Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956

Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999

Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl

Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/

TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809

Last edited by budm; 02-10-2021 at 02:33 PM..
budm is offline   Reply With Quote
Old 02-12-2021, 08:10 PM   #9
debugtimog
Member
 
Join Date: Jul 2018
City & State: Kedah
My Country: Malaysia
I'm a: Knowledge Seeker
Posts: 30
Default Re: Magneto-resistor Digital Output Potentiometer

Hi Budm,
Attached is the scanned copy, I am not sure if I can post the make and model since might be infringement. It is a wafer inspection machine in which the wafer is being tilted in x and y axis. Also going up and down for more focus on the microscope. The old sensor is not accurate anymore and when I tested it, at the max point is 3.7V only as compare with good of 4.5v with input of 5v. the min is within range of 1.3v as compared with the good one of 1.5v.
Again I am looking for advice if anybody is familiar with magnetoresitor/AMR technology. What is digital output for this device means. The OEM said that this is obsolete and they a new technology that uses inductance, still contactless but analog. According to the schematic, I dont think it will misbehave as long as there is voltage coming in to that OpAMp, digital or analog?
Attached Files
File Type: pdf crop.pdf (288.9 KB, 3 views)
debugtimog is offline   Reply With Quote
Old 02-13-2021, 03:07 PM   #10
redwire
Badcaps Veteran
 
Join Date: Dec 2010
City & State: Alberta
My Country: Canada
Posts: 1,993
Default Re: Magneto-resistor Digital Output Potentiometer

The "digital" sensors are a switch, on/off. The "analog" sensors are a continuous voltage output. I think the Japanese manufacturer got confused which type of sensor you are looking for: not inductive, not digital. It's analog.

For sure your sensor has low output? With 6VDC power, datasheet sensor max is 4.5V+/-0.2V and I can't see if it runs from 5V or 10V power. Its output goes to TPOT TP46?
Low output can be caused by: a bad MR sensor, weak magnet, or a large magnet air gap, or a bad op-amp U106 uPC4074 (not likely unless ESD damage) loading down the MR sensor.

The original circuit board has provision for calibration, there are trimpots to cover a wide range of sensor specs. You might be able to calibrate to get this sensor to work, assuming it did not drift or age badly. It might even have been this way all along: 1.3V to 3.7V

Does the board calibrate?
VR4 is gain (inverted)
VR5 Back Offset
VR11 is Offset
JP7 looks like for calibrating TF Offset, whatever that is
VR18 Back Angle gain

I see many optional resistors (with a X cross-out on schematic) that were to accomodate MR sensors with different outputs.
redwire is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump



Badcaps.net Technical Forums © 2003 - 2021
Powered by vBulletin ®
Copyright ©2000 - 2021, Jelsoft Enterprises Ltd.
All times are GMT -6. The time now is 04:28 AM.
Did you find this forum helpful?