Tire Pressure Sensor

Motorola made these -- I don't know if they went to On or FreeFall, but IIRC Digi-Key sells them.

Thanks, I found one for under $20 that goes to 36 psi. As long as it can take about 100% overload without dammage, that may do the trick.

That's correct, for now. But a mandate is coming soon.

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.

Yes, these systems already exist; but all I'm lacking is the sensor itself to make a working device for myself. Also, the commercial ones dont allow for 'leak rate' detection, they only trip a tranmitter on a specific pressure.

This is a killer app for cars 'n trucks. Sensor plus uP plus very low power (eg. Zigbee) wireless interface = big bux for the semiconductor companies. Especially if it gets government mandated.

Best regards, Spehro Pefhany

Some car systems use an indirect method, where they measure RPM of all the wheels via the ABS sensors and, if one wheel begins to roll faster because it's diameter decreases with a pressure drop, it signals an alert.

I suppose the same could be done on a bicycle, using two magnetic pickups and a a form of deluxe speedometer that also does the speed comparision and alerting.. It won't give you the absolute pressure, and it only works if ONE tire loses pressure.

To reply, please remove one letter from each side of "@" Spammers are VERMIN. Please kill them all.

Hello Spehro,

It already exists. One of the guys on the German electronics forum (Oliver Bartels) developed such a system. I believe he also used to race Formula One rods so he should know what he's talking about. Unfortunately the pubs are only in German:

In that article it is mentioned that the US mandates it already but I doubt that.

I can see this for car tires although I check mine every other week. But for bicycles? On mine I just sit on it and then I know. Usually the pressure is digital. It is either ok, or it went kapoof.

Regards, Joerg

It won't.

Well- the air volume is so small that it takes next to nothing to lose pressure- they should be checked before every ride anyway- along with a quick inspection of the frame for cracks. A gauge should be integral to your pump- I have found that it is real easy to make that tire explode with the hand pump- and then you will be hearing impaired for a few hours or so.

In Boston, no ultrasonics need, they park by ear... clang, clang ;-)

...Jim Thompson

I had a '61 Dauphine with tubular wrap-arounds that offered substantial protection.

...Jim Thompson

Thanks, that's definitely worth checking out.

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

Yeah, in the US it's been mandated for most vehicles in 2008.

Another gadget to keep up safe! Jeesh, what ever happened to checking your tire pressure weekly? The idiots seem to be driving our technology. More junk to break down and have fixed for yearly inspection.

Al

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.

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

Hello Al,

Common sense seems on the way out. I mean, if people even need a reminder on coffee cups "caution - HOT - can cause serious injury".

In Europe some folks think they can't even live without ultrasound parking aids in the bumpers. Oh man.

Regards, Joerg

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.

Regards, Joerg