Tire Pressure Sensor

[Luhan Monat]

You can get a digital tire pressure gage with LCD readout at
walmart for ~$10. From there you would need to do some hacking to
get something useful for your application.

Thanks, that's definitely worth checking out.

 

[Jim Thompson]

Instead of pressure, how about measuring how flat the tyre is ? Insert into
the valve stem a sort of plunger that is spring loaded against the inner
tube and tyre. Every time the wheel goes round the plunger will be
compressed and released. You could make the motion generate a voltage to
turn the electronics on, and then measure the change in inductance to get
the actual distance moved. You might even be able to extract enough power to
power a short transmit burst, and hence need no batteries ...

You would need a filter for an alarm so that the odd bump didn't register,
but a gradual change would ...

Dave

Not bad! But why not a fixed, but compressible, rod as part of the
wheel structure? If it touches repetitively, set off an alarm.

...Jim Thompson

 

[Luhan Monat]

Not bad! But why not a fixed, but compressible, rod as part of the
wheel structure? If it touches repetitively, set off an alarm.

...Jim Thompson

I've just realized that I dont need to transmit any data. I can just
put the whole alarm including pizo noisemaker on the wheel itself
(mounted near the hub). The PIC can wake up every 10 seconds or so,
take a reading, determine if there is a leak, and sound the alarm.

Much thanks for all the ideas.

 

[Joerg]

Hello Luhan,

I've just realized that I dont need to transmit any data. I can just
put the whole alarm including pizo noisemaker on the wheel itself
(mounted near the hub). The PIC can wake up every 10 seconds or so,
take a reading, determine if there is a leak, and sound the alarm.

Then the bike becomes like "modern" cars. One day, after not having used
it for a while, you come into your garage and something is going
beeeeep......beeeeep......

Regards, Joerg

 

[Jim Thompson]

I've just realized that I dont need to transmit any data. I can just
put the whole alarm including pizo noisemaker on the wheel itself
(mounted near the hub). The PIC can wake up every 10 seconds or so,
take a reading, determine if there is a leak, and sound the alarm.

Much thanks for all the ideas.

Actually, the BIG GUY plan is that tires will come from the
manufacturer with an RFID tag and pressure sensor installed.

...Jim Thompson

 

[Doug Warner]

Then the bike becomes like "modern" cars. One day, after not having used
it for a while, you come into your garage and something is going
beeeeep......beeeeep......

Centrifugal switch, or accelerometer. So it only draws power (and
alarms) while moving.

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[Paul Hovnanian P.E.]

Hello Luhan,


True. But when I was in driving school they still taught us how to watch
for weird behavior of the vehicle. Low pressure, ice, slush etc. They
also taught us how to react.

Most cars are pretty good though. I was at a customer, had half their
R&D Department in a rented Saturn L300 when the right rear decided to
deflate on a county road. None of us even felt much until we were
parked, except that the car became somewhat sluggish. It remained
remarkably stable.

I've had a rear tire sidewall blow out on a Toyota Landcruiser at 70
mph. No problems. It just settled down on the rim. Don't slam on the
brake or steer suddenly and it handles just fine.

 

[Paul Hovnanian P.E.]

Trouble is, slow leaks are hard to spot while riding until its way too
late. This is a real issue, worth doing an RF/Micro system on the rear
wheel (which tends to get all the leaks). Test for both pressure level,
and change in pressure to warn as much ahead as possible.

I already have a micro based alarm system activated by RF remote. So, I
only need to do the hard work on the transmitting end. Something
sending out a code every 10 turns of the wheel or so to save on battery.

I wonder if something along the lines of an RFID chip in the wheel might
be more reliable. No batteries to worry about, it would be powered by
the stationary transceiver.

 

[Paul Hovnanian P.E.]

Centrifugal switch, or accelerometer. So it only draws power (and
alarms) while moving.

A tiny generator with an unbalanced weight on the shaft. The generator
spins with the wheel, is shaft is held stationary by the weight (like a
self winding watch).
The generator keeps a small supercap charged and wakes up the monitor
logic when it begins turning.

One could conveivably extract enough power from such a setup to power a
small LED display on the wheel, similar to one of those spinning clocks.
Something I know we all need.

--
Paul Hovnanian mailtoaul@Hovnanian.com
------------------------------------------------------------------
It's easier said than done.
.... and if you don't believe it, try proving that it's easier done than
said, and you'll see that it's easier said that `it's easier done than
said' than it is done, which really proves that it's easier said than
done.

 

[Luhan Monat]

A tiny generator with an unbalanced weight on the shaft. The generator
spins with the wheel, is shaft is held stationary by the weight (like a
self winding watch).
The generator keeps a small supercap charged and wakes up the monitor
logic when it begins turning.

One could conveivably extract enough power from such a setup to power a
small LED display on the wheel, similar to one of those spinning clocks.
Something I know we all need.

This suggests another project. Timed LED's on the wheel that make
patterns or spell out messages at night. Devices such as this are
generally known as 'propeller clocks'.

 

[Michael]

Hello Luhan,


Then the bike becomes like "modern" cars. One day, after not having used
it for a while, you come into your garage and something is going
beeeeep......beeeeep......

Regards, Joerg

No, that'd not be good. But not as silly as "Your (door; trunk; whatever) is
ajar".

 

[Mac]

This suggests another project. Timed LED's on the wheel that make
patterns or spell out messages at night. Devices such as this are
generally known as 'propeller clocks'.

Actually, I think this would would be good for automotive hubcaps. I think
people would buy them by the thousands if they were cheap enough, and if
there were an easy way to put messages or graphical displays on them.

I wouldn't try to extract power from the rotation, though. I would
just sense the rotation to keep the message upright.

--Mac

 

[Spehro Pefhany]

I think I've seen this done, though perhaps not as a commercial
device.

Actually, I think this would would be good for automotive hubcaps. I think
people would buy them by the thousands if they were cheap enough, and if
there were an easy way to put messages or graphical displays on them.

I wouldn't try to extract power from the rotation, though. I would
just sense the rotation to keep the message upright.

--Mac

As mechanical devices, these exist. They have some kind of gravity
mechanism and a pivot so they always stay (more or less) vertical.
Yahoo shelled out a bunch of investors' bux to have hundreds (maybe
thousands) of Toronto taxis display their purple message at hubcap
level. LEDs would be more eye-catching, but would require a power
source at the wheel.


Best regards,
Spehro Pefhany

 

[John Woodgate]

I read in sci.electronics.design that Spehro Pefhany

LEDs would be more eye-catching, but would require a power source at
the wheel.

Well, there are fixed and rotating members there, so it's not
impossible.

 

[Si Ballenger]

Actually, I think this would would be good for automotive hubcaps. I think
people would buy them by the thousands if they were cheap enough, and if
there were an easy way to put messages or graphical displays on them.

I wouldn't try to extract power from the rotation, though. I would
just sense the rotation to keep the message upright.

The below hokeyspokes could probably be adapted to the car tire
hub caps. Back in the 50's you could get hub caps with bearings
and a weighted bottom. It stood still while the tire rotated. I
remember a 55 ford crown vic with this setup. Lowered in the rear
with finder skirts, and the non rotating hub caps on the front.
The hub caps were very big with a picture of a hula girl on them.
Had lights in the front findre wells so you could see the action
at night. Where is my Brill Cream?

http://www.drewish.com/blogger/archives/2005/03/17/2sided_pov_toy.html
http://www.hokeyspokes.com/index.shtml
http://www.treehugger.com/files/2004/12/spoke_n_wheel_l.php

 

[Doug Warner]

A tiny generator with an unbalanced weight on the shaft. The generator
spins with the wheel, is shaft is held stationary by the weight (like a
self winding watch).

No need to go to that length, I have a SmartTire system installed on
my car. The in--tire sensor/transmitters use a pair of lithium coin
cells and last for many years. They transmit every several seconds
for about 5 minutes after starting off, then every 5 minutes. The
receiver lives in the center console.
A bicycle unit, with beeper, could be built into a module that just
screws onto the valve stem.

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[Rich Grise]

Hello Luhan,


True. But when I was in driving school they still taught us how to watch
for weird behavior of the vehicle. Low pressure, ice, slush etc. They also
taught us how to react.

Most cars are pretty good though. I was at a customer, had half their R&D
Department in a rented Saturn L300 when the right rear decided to deflate
on a county road. None of us even felt much until we were parked, except
that the car became somewhat sluggish. It remained remarkably stable.

I blew a rear tire on a '76 Plymouth Gran Fury at about 60 MPH once, and
hardly felt it - I knew mainly from the sound. ("What's that noise? Oh!
I've got a blown tire!") I changed the tire in the left-hand breakdown
lane, and the spare was too low to drive on, so I waited for one of those
"highway helper" trucks to come by with some air. When I took the blown
tire, which was basically shreds on a rim, to the tire place, I asked the
tire guy, "Think you can patch that?" He said, "Uh, I don't really think
so - maybe a tube!" ;-)

Cheers!
Rich

 

[Joerg]

Hello Paul,

I've had a rear tire sidewall blow out on a Toyota Landcruiser at 70
mph. No problems. It just settled down on the rim. Don't slam on the
brake or steer suddenly and it handles just fine.

That's exactly what they hammered in. Same as driving on a road where
ice or slippery goo shows up late in the game. Keep the control, don't
panic. This was all pre-ABS and once the brakes locked up there was
hardly anything left to recover.

Regards, Joerg

 

[Joerg]

Hello Paul,

A tiny generator with an unbalanced weight on the shaft. The generator
spins with the wheel, is shaft is held stationary by the weight (like a
self winding watch).
The generator keeps a small supercap charged and wakes up the monitor
logic when it begins turning.

That's pretty slick. But also expensive.

Regards, Joerg

 

[Joerg]

Hello Doug,

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Spammers are VERMIN. Please kill them all.

Your wish may have been heard. I read in the papers today that a judge
gave one of them a whopping nine years. I think that's a bit much and he
is appealing but it does send a message.

Regards, Joerg