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Tire Pressure Sensor

Discussion in 'Electronic Design' started by Luhan Monat, Apr 7, 2005.

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  1. Luhan Monat

    Luhan Monat Guest

    Hi,

    I would like to make a remote tire pressure monitor (0-50 psi) for my
    bicycle. Any ideas on where to get a sensor cheap? Accuracy is not
    critical, as long as temperature drift is not excessive.
     
  2. Tim Wescott

    Tim Wescott Guest

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

    Luhan Monat Guest

    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.
     
  4. 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
     
  5. Joerg

    Joerg Guest

    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:

    http://www.tyretronic.com/index.php?m=200202___AANDE_200201&language=en

    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
     
  6. Fred Bloggs

    Fred Bloggs Guest

    It won't.
     
  7. Doug Warner

    Doug Warner Guest

    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.
     
  8. Fred Bloggs

    Fred Bloggs Guest

    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.
     
  9. That's correct, for now. But a mandate is coming soon.
     
  10. Luhan Monat

    Luhan Monat Guest

    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.
     
  11. rob

    rob Guest



    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.
     
  12. Al

    Al Guest

    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
     
  13. Si Ballenger

    Si Ballenger Guest

    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.
     
  14. Joerg

    Joerg Guest

    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
     
  15. Jim Thompson

    Jim Thompson Guest

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

    ...Jim Thompson
     
  16. Joerg

    Joerg Guest

    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
     
  17. Joerg

    Joerg Guest

    Hello Rob,
    We did something similar for a large diesel drive shaft, to measure
    torque flutter etc. which could indicate upcoming engine problems.
    Balanced strain gauge on the shaft, inductive coupling to a stationary
    coil. No micro, no Zigbee, no battery. Well, neither Zigbee nor
    Bluetooth were around at that time anyway.

    Regards, Joerg
     
  18. Al

    Al Guest

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

    Al
     
  19. Jim Thompson

    Jim Thompson Guest

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

    ...Jim Thompson
     
  20. Dave Garnett

    Dave Garnett Guest

    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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