Automotive Project 1

[tansis]

A recent search of the web turns up that checking tyre pressures is one of the most unwanted jobs facing owner / drivers of motor vehicles. Despite being a simple check to perform it it often forgot or rather bypassed with
a visual inspection with the possability of some percussive testing...
(go on, admit it, how many of you have kicked the tyres of a car?)

When a car tyre fails it is bad enough, but walk down the hard shoulder
of a freeway /motorway/ highway and soon enough you will come across
substantial chunks of rubber from a truck tyre, roughly the size of dinner plate wieghing close to kilo they don't bounce well on impact, particularly
with a windshield. I know, time is money to trucker / haulage operator but checking tyre pressures is a task that should be perfomed with each new load, not once a week or month or five minutes before the annual government inspection.

By now I've upset all the truckers, well let me really stick in your craw now, I analyse tachograph records, so like Santa I know whose been naughty this year :lol:

Anyhow griping aside...a suggestion for a project

The challenge....

to design a device that can measure tyre pressure, mounted internally to the wheel rim or externally on the valve and relay this information to a display in the cab of the vehicle.

Low power consumption a must for battery powered operation,
inductive power transfer solutions are more than welcome
and bear in mind in commercial operations tractor units are
not dedicated to a particular trailer.

 

[JohnBrown]

I think you'll find that a lot of the big boys are working on this right now, since it's going to be mandatory in the US shortly.

 

[stevez]

About 5 yrs ago I found an IC that was made for this purpose. I was working on a way to improve the reliability of air chucking on a large machine. I contacted the manufacturer's of the air chucks and their response at the time was "we're working on it." Sorry I can recall who made the IC.

 

[tansis]

Just because the "big boys" are working on idea does not mean
a talented amatuer or group of them cannot come up with a
more innovative design.

Besides if EU legislation is anything to go by they will need all
the help they can get..

Behold the spec sheet from hell :twisted:
for a single channel data logger, all 500 pages!
Thankfully member states are still arguing the finer points.

**broken link removed**

 

[JohnBrown]

Just because the "big boys" are working on idea does not mean
a talented amatuer or group of them cannot come up with a
more innovative design.

My post was supposed to be informative. I never said that a talented amateur could not come up with a more innovative solution. It might, nevertheless, be worth your while to investigate the current state of the art. No sense in re-inventing the wheel (or anything associated with it).

 

[DirtyLude]

MicroChip actually has an AppNote for this exact application, using their rfPics.

https://www.electro-tech-online.com/custompdfs/2004/11/00238b.pdf

 

[tansis]

Although last year's court decision has created some indecision regarding TPMS-implementation schedules :wink:

NHTSA's tests on commercially available pressure-based TPMS (direct systems) yielded an advisory message at an average of a 20% underinflation level and a safety warning at 36% below recommended pressure. Again, significant differences existed in response times that varied from 8 to 136 sec. The EU believes that temperature measurement is also essential to ensure the long-term accuracy and reliability.
(host of other related problems have been omitted to keep post short)

So some scope for improvement here,
as well as in other areas it would seem

https://www.wired.com/wired/archive/8.03/bikes.html
**broken link removed**
(personally I liked the old deformable version for the Grumman MoLab)

 

[ante]

How about this?
If you are satisfied with an early warning for low pressure just use the ABS sensors. By comparing the left side to the right for each axle you start to get a higher number of pulses from the wheel that is losing pressure since the radius getting smaller. A warning light makes you take the nearest exit to check what’s wrong.
Just a thought! :idea:

Ante :roll:

 

[JohnBrown]

How about this?
If you are satisfied with an early warning for low pressure just use the ABS sensors. By comparing the left side to the right for each axle you start to get a higher number of pulses from the wheel that is losing pressure since the radius getting smaller. A warning light makes you take the nearest exit to check what’s wrong.
Just a thought! :idea:

Ante :roll:

IIRC that IS one of the ideas the 'big boys' are looking into. Like I said, don't waste your time re-inventing stuff.

 

[ante]

Oh yea! Where can I get the information about what the “big boys” are doing so that I don’t step on anybody’s toes?

Ante :roll:

 

[JohnBrown]

To be perfectly honest with you, I can't remember where I read about it. Could have been on the web, could have been in a magazine. I don't have any inside information.

 

[DirtyLude]

Oh yea! Where can I get the information about what the “big boys” are doing so that I don’t step on anybody’s toes?

Ante :roll:

The only ones I know of are for race car data acquisition/logging apps.

But I mean, just doing a quick google search:

**broken link removed**
http://www.piresearch.com/sub_page.cfm/section/products/editID/41
**broken link removed**



Here's a chip solution:
http://www.siliconchip.com.au/cms/A_30287/article.html

Subaru Tire Pressure Monitor details:
http://www.cars101.com/subaru/tiremonitor.html

Fed propose Tire Pressure Monitors:
http://www.consumeraffairs.com/news04/nhtsa_tire_pressure.html

Monitors may be delayed:
http://www.usatoday.com/money/consumer/autos/mauto902.htm

and then I got tired of looking.

 

[ante]

Well John, just like you I can’s seem to find anyone who are using the idea I described here earlier. You sounded very sure about yourself “IIRC that IS one of the ideas the 'big boys' are looking into. Like I said, don't waste your time re-inventing stuff.” And it was absolutely not my intention to waste your valuable time with this!

Thanks

Ante :roll:

 

[Roff]

I don't intend to take sides here, but if you are talking about ABS-based TPMS, it doesn't take much searching to find that it has been available for several years on some vehicles. For example:

https://www.gm.com/company/gmability/sustainability/reports/03/pdfs/sus03pdf_700.pdf

There are others as well.

 

[JohnBrown]

There are no sides to take, as far as I'm concerned. I have no axe to grind in this matter.

 

[ante]

Thanks Ron, I’ll try to find more info on the TPMS system since the pdf was very superficial on the subject. I did not know there where something like that going on since I have seen plenty of “transmitter in rim” type. I don’t know why they want to trouble themselves with something like that which must be powered in some way and transmit vital info through all the interference that are present in the cars environment. It must be much easier to have something hardwired into the car electronics. I drive GM and I did not know this!
Thanks again!

Ante :roll:

 

[Juglenaut]

I thought of something, but I digress. Actually two ideas in one...

 

[zevon8]

I remember this becoming a feature in the late 80's, I think it was on Corvettes. This was around the same time as the computer controlled servo suspensions were hitting the market.

One reason I seem to recall for using a transmitter, was that in the case of low-profile tires, with stiff side walls, there may be very little change in diameter with a small change of air pressure. Well, atleast the calculations based on rim RPM differential would be more difficult anyways.

 

[ante]

Hi Zevon,

If just one lap of the wheels is compared it will be hard to get a safe value. However there are quite a lot of pulses per rpm from the sensors so the slightest change of the radius will certainly become evident in a few hundred meters. A circuit that compares the number of pulses would not be very complicated I think.

Ante :roll:

 

[zevon8]

True, Ante, it would not be that hard to do. Adding to the problems if I recall correctly, was separating the numbers from the "noise." Small variations mixed with different turning speeds, etc, made for complicated math, when including all the variables. Having to compare pressures over time as the air heated, etc. At least a separate sensor only needs to check pressure, and compare it to a value for a given temperature.

I wonder if the advent of low profile "run-flat" tires requiring a pressure sensor brought the cost of a separate technology down to the point that having the vehicle computer do the monitoring was no longer worth it?

It is an interesting question... the more you ponder the more questions you think of...