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'[EE]: Differentiating gravitas from axel-ration.'
2005\09\01@161301 by Gus Salavatore Calabrese

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I am really happy to read all the useful and inciteful ideas put forth.

 I realize I did not supply enough information in my original post.

---->  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 ?   <---

My desire is to build a product that will sell for $30-$50 max.  Less  
would be great.
The product requires NO skill to install.  If it requires power that  
could come from the
cigarette lighter socket.  The user can put it in the back window or  
mount it anywhere
they want.
The desired result is to have the light FLASH to alert other drivers  
to wake up.
False positives are not that bad.  False negatives are to be avoided.
If it works correctly 90% of the time it is certainly better than  
"nothing".

Your comments made me realize that another product could measure the
speed at which a car was approaching the rear and flash the brake lights
if the closing vector was excessive.  In addition, if an Italian  
driver ( note
my last name ) is following on the bumper, the light would flash.

( on a side note: I actually got a driver following me to use his  
turn signals today,
by repeatedly striking the side of my head with my open palm.  He  
started using his
signals and he also flipped me off.    see
urbanlegends.about.com/b/a/007882.htm  )


ALL OF MY COMMENTS / TEXT/ IDEAS ARE PUBLIC DOMAIN.  PLEASE FEEL FREE  
TO USE THEM.


I really apppreciated Bills comment

\Isn't "x-axis" acceleration due to typical hills liable to be MUCH
smaller than acceleration caused by  even gentle breaking?  Maybe
you can get by with a simple threshold.  Have you measured the sorts
of values that actually occur instead of getting hung up on theory?

BillW

Also the one about a strain-gauge on the brakeline
Possibly the one about monitoring the brake-light will work.
And vibration sensing to calibrate.



yes, inciteful is a pun




Augustus Gustavius Salvatore Calabrese 720.222.1309    AGSC
http://www.omegadogs.com   Denver, CO

Disclaimer: The above statements are not intended as an endorsement of
any kind and any inference of having any verifiable knowledge about
anything referenced above is purely coincidental. ( we hope )

If you are not part of the solution, you are precipitate.





2005\09\01@165114 by Rich Mulvey

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Gus Salavatore Calabrese wrote:

{Quote hidden}

  While I'm aware that The World Is A Very Big Place, I have to wonder
how many places, like my state, restrict the use of blinking lights in
civilian vehicles, other than turn signals.

- Rich

2005\09\01@171810 by David Van Horn

picon face
>    While I'm aware that The World Is A Very Big Place, I have to
wonder
> how many places, like my state, restrict the use of blinking lights in
> civilian vehicles, other than turn signals.

As one who has such lights installed, I can tell you it's a whole
'nother can of worms!  Some jurisdictions don't seem to mind, others are
much more uptight about it.  Here in Indiana, one may have red, or white
strobes to the rear, white to the front, and yellow all around, without
any special permits. They are considered essentially an enhanced
"emergency blinker".   I have them because of my Skywarn involvement.  I
get just as much authority in traffic with them as a tow truck would
(none!)

I can imagine other places where you could end up in a very bad mess
over something like this.  In Virginia, I am told that even the police
aren't allowed computers and similar devices that can be seen by the
driver.
Sort of an Amish approach to law enforcement I guess....





2005\09\01@175751 by Robert Rolf

picon face
If you want an 'idiot proof' system with negligible installation
requirements, use the same technology as that found in
 'radar' door openers (X-band RF to get narrow beams).

Using doppler off the road surface (oblique angle measuring),
you can measure vehicle velocity directly, and thereby the
rate of change of velocity to detect acceleration and braking.

By measuring the rate of closing of a following vehicle
(again with X band radio waves), you have part two of your
product (follow too close warning).
The typical alarm X-band motion sensor works out to
about 40 feet for human sized objects, which should be far
enough for what you want to detect (big metal car).
A dielectric lens can increase this range substantially.

By mounting both waveguides orthogonally in a waterproof package
that mounts to the rear bumper, and perhaps using wireless
communications (if not hard wired) with your flashing lights
indicator, you have what you describe.

The problem is your target price. I don't see how to make it
as cheap as you want except in huge quantities.

RF motion sensors as used in alarm systems are in the $40
range. (x2) You need an indicator bank ($10), and a some processor
(presumably a PIC) to tie it all together. And then there is
packaging and profit.

In North America there is a requirement for all new vehicles to
have a eye level mounted brake light. This has worked well to
reduce the rear end accident rate. Inexpensive retrofit kits
were available in the years following the regulation.
Since you are in Denver, CO, I'm not sure how your device would
improve things.

There IS a way to use just ONE RF sensor/waveguide for both functions.
Contact me offlist for the technical details.

Please send any royalties my way.

Robert

P.S. The use of a variable rate blink to show braking rate
is the subject of a 1950's patent, which will count as 'prior art'
should you try to patent this anywhere.

Rich Mulvey wrote:

> Gus Salavatore Calabrese wrote:
>
>> I am really happy to read all the useful and inciteful ideas put forth.
>>
>>  I realize I did not supply enough information in my original post.

Seems to be a common problem on the PICLIST.

{Quote hidden}

2005\09\02@032904 by PicDude

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On Thursday 01 September 2005 03:13 pm, Gus Salavatore Calabrese scribbled:
> My desire is to build a product that will sell for $30-$50 max.  Less
> would be great.

Pricing will depend significantly on volume.


> The product requires NO skill to install.  If it requires power that
> could come from the
> cigarette lighter socket.  The user can put it in the back window or
> mount it anywhere
> they want.
> The desired result is to have the light FLASH to alert other drivers
> to wake up.

Be careful with this -- we looked into doing this some years ago (using a
pedal-position sensor), but found out that there are laws against this.  In
places that prohibit this, if you build a one-off for yourself, you'll
probably get a warning or ticket, but as a commercial product you get sued if
someone else gets a ticket.  Not sure what the rules are for every state
(assuming you are in the U.S.), but I remember a law regarding flashing
lights being on police/government vehicles only, except for things like tow
trucks etc could have orange flashing lights only -- no blue or red.  Another
law limits lights on vehicles to "only what is necessary" (paraphrased) for
operation -- so in those places things like under-car neon are illegal.  We
were also worried that if someone rear-ends a person with this flashing
light, they could sue and claim that it was confusing.  Being non-stardard
lighting, you'd probably lose.  You really need to check the laws for this.

Cheers,
-Neil.



2005\09\02@052700 by Russell McMahon

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>> The desired result is to have the light FLASH to alert other
>> drivers
>> to wake up.

FWIW units that did this were sold in Australia in about 1977!. AFAIR
they were named "Cyberlight". They were VERY bright at first. Taxis
tended to use them. People complained about the brightness and they
were toned down.

       RM

2005\09\02@104337 by Howard Winter

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picon face
Rich,

On Thu, 01 Sep 2005 16:51:00 -0400, Rich Mulvey wrote:

> While I'm aware that The World Is A Very Big Place, I have to wonder
> how many places, like my state, restrict the use of blinking lights in
> civilian vehicles, other than turn signals.

I thought this right at the beginning, but got distracted by the physics discussion!  Over here ordinary
vehicles have flashing turn indicators, and as a hazard warning they can all flash together when the vehicle
is stationary (even though a lot of people use them to indicate problems when moving, strictly this isn't
allowed).  

Otherwise you have to be a hazardous vehicle (towing, or with a large or slow-moving load) to have flashing
amber, an emergency vehicle on a shout (Fire, Police, Ambulance, Rescue, Bomb Disposal, blood or medical
supplies) to have flashing blue, or a doctor or other medic to have flashing green - the latter usually in
their own cars when they are called-in to an emergency.  

Doing the hazard-flashing thing every time you slow down would confuse and annoy other drivers, and you'd get
pulled up by the first police car to see you do it.  You wouldn't get away with flashing the brakelights
themselves either, because the regulations say they must come on when you apply the brakes, and flashing isn't
"on"!  You might get away with additional brakelights whose brightness indicates the rate of decelleration,
but I think even this would be frowned on.

I seem to remember seeing an American car that had three pairs of brakelights, and they came on in sequence in
proportion to the level of braking, but I'm not sure it did any good.

Cheers,


Howard Winter
St.Albans, England


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