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[DPRG] [DMS] Using HDD read/write heads as magnet sensors?

Subject: [DPRG] [DMS] Using HDD read/write heads as magnet sensors?
From: A. Scientist angryscientist at gmail.com
Date: Thu Oct 13 13:33:22 CDT 2011

I have 4-5 you could have, but you cant have the platters and im really lazy
about taking them out ;)

On Thu, Oct 13, 2011 at 1:07 PM, Chuck McManis <cmcmanis at mcmanis.com> wrote:

> On Tue, Oct 11, 2011 at 6:02 PM, Oguz Yetkin <oyetkin at gmail.com> wrote:
>
>> I'm interested in the more recent sensors, which, to the best of my
>> understanding, use Giant MagnetoResistance (GMR) effects to read the
>> magnetism.
>>
>> What I don't know how to do is to interface with the electronics.  I
>> suppose I'll have to rip out a read head or two and hook it up to a DAQ
>> system with some applied voltage (which may, of course, prove to be naive).
>>   You're probably right about the local sensitivity, which actually would be
>> a plus for me.
>>
>> Which leaves me with the question:  does anyone have any hard drives
>> (preferably recent) I can take apart? :)
>>
>
> The good news is that 'dead' drives are really really easy to find.
> Probably any computer store, certainly and company of any size their IT
> department will have some. The not so good news is that the driver for the
> read/write heads is built into the servo control chip which is on the
> mainboard of the disk drive and is a completely proprietary part. So what
> that leaves you with if you take the leads directly from the disk arm is a
> fairly sophsiticated pre-amplifier stage, probably a flash adc and a small
> DSP to convert what the head 'can see' into something you can use.
>
> --Chuck
>
>
>
>>
>> Oguz
>>
>>
>> On Tue, Oct 11, 2011 at 7:38 PM, Jonathan Shook <jshook at gmail.com> wrote:
>>
>>> No, I have no experience with this, but I do have conjecture, for what
>>> it's worth (not much).
>>>
>>> I'm assuming:
>>> It may may be sensitive, but the proximity to the disk is very important,
>>> so that the local field bias has a greater influence on the read sensor than
>>> ambient EMF.
>>> The ability to detect field bias may be more useful than a large dynamic
>>> range in the design of the read head.. so your applicability may be hit or
>>> miss.
>>> The sense time of the head has to be extremely low, suggesting extremely
>>> low impedance, and likely a dependence on some very specially tuned sensing
>>> logic/amplification.
>>>
>>> BUT, I would suggest you ask Ben about this, because he is the most
>>> likely expert among us.
>>>
>>>
>>> On Tue, Oct 11, 2011 at 6:07 PM, Oguz Yetkin <oyetkin at gmail.com> wrote:
>>>
>>>> Hello,
>>>>
>>>> It just dawned on me that the read/write had on a modern Hard Disk Drive
>>>> might contain a more sensitive magnetism sensor than what I have been buying
>>>> as separate components online (ratiometric Hall Effect sensors).
>>>>
>>>> Does anyone here have any experience reading from an old HD read head?
>>>>  I've been searching the Arduino forums, etc. but most of what I've found
>>>> concerns controlling the positioning of the heads
>>>>
>>>> These are the closest things I could find to 'useful'
>>>>
>>>> HDDJ: Turning an HDD into a rotary input device (involves reading the
>>>> motor)
>>>>
>>>> http://www.instructables.com/id/HDDJ-Turning-an-old-hard-disk-drive-into-a-rotary/
>>>>
>>>> Involves controlling head positioning
>>>> HD Laser Display
>>>> http://spikenzielabs.com/SpikenzieLabs/Laser_Display.html
>>>> HD Oscilloscope
>>>> http://hackedgadgets.com/2006/04/25/top-5-uses-for-a-dead-hard-drive/2/
>>>>
>>>> As always, any help/insight is appreciated.
>>>>
>>>> Thanks,
>>>>
>>>> Oguz
>>>>
>>>> _______________________________________________
>>>> DMS mailing list
>>>> DMS at lists.dallasmakerspace.org
>>>> http://lists.dallasmakerspace.org/listinfo/dms
>>>>
>>>>
>>>
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>>>
>>
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>
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