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'Looking for method to differentiate gravity from a'
2005\08\31@112606 by olin piclist

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Gus Salavatore Calabrese wrote:
> I see no way to differentiate between braking and going downhill. Any
> ideas ?

Check the depth the brake pedal is pressed.

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2005\08\31@174027 by Jason

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From: "Gus Salavatore Calabrese" <spam_OUTgscTakeThisOuTspamomegadogs.com>
Sent: Wednesday, August 31, 2005 8:00 AM

> I have been designing a vehicle tail light which would start flashing
> at a slow rate
> as the brakes were applied and at a faster rate as the brakes were
> applied harder.
> Ideally this unit would be standalone except for power ( which might
> be solar provided ).
>
> I see no way to differentiate between braking and going downhill. Any
> ideas ?

Do you mean you want to use some sort of accelerometer to measure breaking?

According to our modern understanding of physics there is no difference
between acceleration and gravity.  If you are in a box with no windows and
no way to see what's going on outside the box, there is no possible
instrument that could be built to tell you if you're tipping forwards or
accelerating backwards (slowing down if you're moving forwards).

Jason


2005\08\31@203342 by Peter van Hoof

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I think everyone here is looking for way too complicated solutions to a simple
problem

A thing that you overlook is that uphill downhill is a slow event while
aggressive braking that these devices are supposed to warn for is a slow event

Detecting rate of change rather than absolute value would probably work


Peter van Hoof


{Original Message removed}

2005\08\31@204147 by Peter van Hoof

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An error in my message, it should read :
A thing that you overlook is that uphill downhill is a slow event while
aggressive braking that these devices are supposed to warn for is a FAST event

{Original Message removed}

2005\08\31@205401 by David Van Horn

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> An error in my message, it should read :
> A thing that you overlook is that uphill downhill is a slow event
while
>  aggressive braking that these devices are supposed to warn for is a
FAST
> event


Driving in San Fransisco..

I don't know what the slopes are, but they are truly impressive.

This one pegs Lombard street at 40 degrees, with eight 180 degree
switchbacks. Another one pegs it at 45 degrees.
http://members.virtualtourist.com/m/980ba/b870f/

A technical bicycling article gives some interesting numbers.
http://www.keck.ucsf.edu/~dblake/grades.txt


2005\08\31@210426 by Peter van Hoof

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The question is would it be so awful if the lights would indicate fast braking
if you barrel down a 45 degree slope when you hit a flat intersection and I
would say no, chances of that happening are not that big either. We are not the
"Dukes of Hazard"

Peter van Hoof

{Original Message removed}

2005\08\31@212550 by David Van Horn

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> -----Original Message-----
> From: .....piclist-bouncesKILLspamspam@spam@mit.edu [piclist-bouncesspamKILLspammit.edu] On
Behalf
> Of Peter van Hoof
> Sent: Wednesday, August 31, 2005 8:04 PM
> To: Microcontroller discussion list - Public.
> Subject: Re: Looking for method to differentiate gravity from
acceleration
>
> The question is would it be so awful if the lights would indicate fast
> braking
> if you barrel down a 45 degree slope when you hit a flat intersection
and
> I would say no, chances of that happening are not that big either. We
are
> not the "Dukes of Hazard"


What I think would happen, is that it would indicate that I was braking
hard when I was just coasting down, and if I braked hard going uphill,
it would probably miss that.

Safety equipment that is unreliable, is worse than no safety equipment.



2005\08\31@215927 by Peter van Hoof

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David Van Horn wrote:

> What I think would happen, is that it would indicate that I was braking
> hard when I was just coasting down, and if I braked hard going uphill,
> it would probably miss that.
>
> Safety equipment that is unreliable, is worse than no safety equipment.

I dont think you get what I am trying to describe,

Immagine an accellerometer measuring gforce in the forward direction

If you start going downhill a accelerometer would gradually go from for example
from 0g to 0.5g ( a gentle rollercoaster ) this would take several seconds and
rate of change would be small and lights would not trigger, hitting the brakes
would bring the 0.5g to 0.6 in a few tenths (hundredths) of a second  and would
trigger the lights.

Similarly going uphil , a gentle rate of change from 0g to -0.5g the rate of
change low (also in the wrong direction), no lights. now hit the brakes -0.5g
to -0.4g in a few hundredths of a second. That's a high rate of change , so
brakes and lhe lights go on.

Peter van Hoof


2005\08\31@221147 by David Van Horn

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Ah. Delta acceleration might work.. Speedbumps and such could be
filtered out I think.  

Good idea.  Also, where you have a large delta in acceleration, some
cautionary flashes might not be a bad idea.


> {Original Message removed}

2005\08\31@231551 by Oscar T.

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>
> Immagine an accellerometer measuring gforce in the forward direction
>
> If you start going downhill a accelerometer would gradually go from for example
> from 0g to 0.5g ( a gentle rollercoaster ) this would take several seconds and

Ok, the car is increasing its acceleration as slope becomes but inclined.

> rate of change would be small and lights would not trigger, hitting the brakes
> would bring the 0.5g to 0.6 in a few tenths (hundredths) of a second  and would

now he even increase their aceleration, push the wrong pedal ?

case b :
Let start again, a positive g means decelaration.

> If you start going downhill a accelerometer would gradually go from for example
> from 0g to 0.5g ( a gentle rollercoaster ) this would take several seconds and

The driver is gentle pushing the brake, actually he is speeding down.

> rate of change would be small and lights would not trigger, hitting the brakes
> would bring the 0.5g to 0.6 in a few tenths (hundredths) of a second  and would

now he even speed down faster.


> trigger the lights.
>
> Similarly going uphil , a gentle rate of change from 0g to -0.5g the rate of
> change low (also in the wrong direction), no lights. now hit the brakes -0.5g
> to -0.4g in a few hundredths of a second. That's a high rate of change , so
> brakes and lhe lights go on.
>
> Peter van Hoof
>
>
> -

2005\08\31@233451 by Oscar T.

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Sorry I scrubbed before ending

>
> Immagine an accellerometer measuring gforce in the forward direction

case a :
   a positive g means acceleration.

> If you start going downhill a accelerometer would gradually go from for example
> from 0g to 0.5g ( a gentle rollercoaster ) this would take several seconds and

Ok, the car is increasing its acceleration as slope becomes but inclined.

> rate of change would be small and lights would not trigger, hitting the brakes
> would bring the 0.5g to 0.6 in a few tenths (hundredths) of a second  and would

now he even increase their acceleration, push the wrong pedal ? ;)

case b :
Let start again, a positive g means deceleration and ...
                      a negative g means acceleration

> If you start going downhill a accelerometer would gradually go from for example
> from 0g to 0.5g ( a gentle rollercoaster ) this would take several seconds and

The driver is gentle pushing the brake, actually he is speeding down.

> rate of change would be small and lights would not trigger, hitting the brakes
> would bring the 0.5g to 0.6 in a few tenths (hundredths) of a second  and would

now he even speed down faster. Ok.

> Similarly going uphil , a gentle rate of change from 0g to -0.5g the rate of

but now, why does he speed up (at an increased acceleration) ?

> change low (also in the wrong direction), no lights. now hit the brakes  -0.5g
>  to -0.4g in a few hundredths of a second. That's a high rate of change

Actually, he does not hit the brakes, he is only accelerating a bit slower.


IMHO, we only need a simple threshold on acceleration, (actually
deceleration) as we want to signal how much rate  we are reducing our
speed.

Cheers


'Looking for method to differentiate gravity from a'
2005\09\01@013610 by William Chops Westfield
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On Aug 31, 2005, at 7:15 PM, David Van Horn wrote:

> Delta acceleration

"jerk", IIRC... (dA/dt)

 :-)
BillW

2005\09\01@014600 by David Van Horn

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> > Delta acceleration
>
> "jerk", IIRC... (dA/dt)
>

Hmm.. I have frequently thought that this was an appropriate term to
use, as I drive around the nation's highways, in various dynamic
situations.






2005\09\01@031413 by Electron

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At 00.49 2005.09.01 -0500, you wrote:
>> > Delta acceleration
>>
>> "jerk", IIRC... (dA/dt)
>>
>
>Hmm.. I have frequently thought that this was an appropriate term to
>use, as I drive around the nation's highways, in various dynamic
>situations.

Did you ever drive in Italy?

I do every day, and I'd prefer to do it in a M1 Abrahms (some of the
drivers I meet would deserve that, expecially those with Alfa Romeo's
or BMW's, who think they're on their own private race track).

What annoys me most is the distance they keep from your butt. Some
stay at no more than 50cm from you at speeds of 100+ Km/h. I'm tempted
to hit the brake pedal hard sometimes, no matter what will happen, so
they get properly educated.

2005\09\01@035600 by David Van Horn

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> -----Original Message-----
> From: .....piclist-bouncesKILLspamspam.....mit.edu [EraseMEpiclist-bouncesspam_OUTspamTakeThisOuTmit.edu] On
Behalf
> Of Electron
> Sent: Thursday, September 01, 2005 3:15 AM
> To: Microcontroller discussion list - Public.
> Subject: RE: Looking for method to differentiate gravity from
acceleration
{Quote hidden}

Taiwan.

> I do every day, and I'd prefer to do it in a M1 Abrahms (some of the
> drivers I meet would deserve that, expecially those with Alfa Romeo's
> or BMW's, who think they're on their own private race track).

My first car was an alfa! :)




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