At the risk of being foolish (working for a Hall Effect company, nothing
here I say represents a company's official position, just my own), no, I
would not expect issues with steel toed boots. Magnetic field intensity
drops inversely proportional to the square of the distance. A steel
toed boot is not normally magnetized, and therefore would not have
fields associated with it; bringing it close may affect fringing lines
but still would have to be within an inch or so to even start to have an
impact. Try holding a magnet near the refridgerator--you won't feel any
force until an inch or so, and that's probably with a super strong
magnet at that.
Now, from what I have seen on the Prius pedal (elsewhere, again not at
work), the two sensors are wired not to give a redundant signal--if one
has an output of 1V, the other is 1V also--but redundant in that one
sensor will always be something like 0.5V above the other. At zero
throttle, one sensor is 0.5V and the other 1V; at full throttle it might
be 4V and 4.5V. The ECU then monitors and should therefore fault if
both sensors ever give the same reading--or 0V, or 5V. This design
doesn't seem to make as much sense as two sensors out of phase with each
other--if one goes up in voltage, the other goes down--but it appears to
be the Toyota method nevertheless.
Actually, found the post:
http://forums.tdiclub.com/showpost.php?p=2888549&postcount=24 There is
other speculation on that thread about the issue, but this single post
does show the inner electricals of the pedal in question.
I did see photos of the pedal taken apart on thetruthaboutcars.com, I
suppose if one wanted to they could go look at the pictures. But ones
steel toed boot is way too far to have any sort of effect on the
sensors.
Shawn Upton, KB1CKT
Test Engineer
Allegro MicroSystems, Inc
[log in to unmask]
603.626.2429/fax: 603.641.5336
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of John Burke
Sent: Thursday, March 18, 2010 5:54 PM
To: [log in to unmask]
Subject: Re: [TN] More on Toyota
Importance: High
You have GOT to be kidding - they use hall effect sensors and magnets to
detect where the pedal shold be!!!!!!!!
Does any one here know if the people experiencing these issues happen to
be
wearing steel toe cap boots?
Best regards,
John Burke
(408) 515 4992
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bob Landman
Sent: Thursday, March 18, 2010 2:43 PM
To: [log in to unmask]
Subject: Re: [TN] More on Toyota
Yes, it's a whitewash job, IMHO. I invited Dr Gilbert to our weekly tin
whiskers telecon last week. He was very humble and forthcoming on what
he
knew and what he did not know.
He shared pictures of the APP (accelerator pedal module) which has SMT
resistors and caps and a small SOIC package that converts two redundant
Hall
sensors that the magnets attached to the pedals move by. That results
in a
1-4Vdc signal. Tin plated connector soldered to the board. Plenty of
locations for whisker shorts to do what Toyota's so-called expert said
"can't possibly happen".
If you would like to see the pictures and his technical report I'd be
happy
to share them with you.
Bob Landman
H&L Instruments, LLC
Sent from my iPhone
On Mar 18, 2010, at 12:48 PM, Chris Mahanna <[log in to unmask]>
wrote:
> Has anyone else reviewed the Toyota slideshow and related PR on the
> Dr. Gilbert debunking?
>
> http://pressroom.toyota.com/pr/tms/document/Exponent_ProfGilbert_8Mar1
> 0.pdf
>
> As part of their "defense" they have totally laid-out the fault tree
> and required sequencing.
> Assuming that it is an under-hood box, with a little material and
> process information (like finish, solder, laminate, compliant pin?) it
> appears to me to likely be a quick FA.
> The fact that there is complete silence about any (IMO obvious) FA
> hypothesis is very intriguing.
>
> Although I have no specific information!, I think it highly unlikely
> that Toyota doesn't know the root (electronic) cause for at least some
> of them.
> If Michael Pecht or one of my competitors has their hands on a faulty
> unit the public should know the answer soon enough. If not, it
> probably means tort beat quality one more time (aren't they supposed
> to work in consort!?)
>
> I think it will be very interesting to see how the legislators and
> regulators handle such a situation.
>
> Chris
>
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