Tire Pressure Sensor

In the 60's, while a student, the massive bumpers on my '47 Pontiac could really dish it out.

Al

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

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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.

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.

What about a small adjustable pressure switch mounted on the valve (counterweight opposite if needed). Thin wire back to a battery mounted near the hub/axle. Then via LED or whatever to a frame mounted sensor which is read every wheel rotation. Sorry no micro or Zigbee.

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'.

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

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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".

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

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

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

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

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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I read in sci.electronics.design that Spehro Pefhany wrote (in ) about 'Tire Pressure Sensor', on Sat, 9 Apr 2005:

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

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?

Hello Paul,

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

Hello Paul,

That's pretty slick. But also expensive.

Regards, Joerg

Hello Doug,

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