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Wireless Heart Rate Monitor

Discussion in 'Electronic Basics' started by Mark Witczak, Feb 16, 2005.

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  1. Mark Witczak

    Mark Witczak Guest

    Hi,

    Does anyone have or is familiar with designing/building a receiver for
    the Polar Heart Rate Monitor transmitter?

    Thanks,
    Mark
     
  2. Thomas Magma

    Thomas Magma Guest

    Are you talking MICS (Medical Implant Communications Service)?
     
  3. Dan Major

    Dan Major Guest

    First, Polar makes a small stand-alone receiver unit for their
    transmitters. The transmitters output a "burst" at 5KHz for each qrs
    detected. At this frequency, you don't use a conventional antenna, but
    rather a resonance-tuned coupling coil. The range is *very* limited (less
    than 2 meters) and is prone to interference. I gave up on the Polar stuff
    and made my own system using off-the-shelf RF modules at 413MHz.
     
  4. Polar is (Swiss) a manufacturer of wristwatch-Heart Rate Monitors
    (HRM) that are used by people working out. They have a separate
    transmitter that straps around your chest, and a receiver in the
    wristwatch. They're a consumer product, albeit a niche one. Their
    manuals are a bit.. opaque.


    Best regards,
    Spehro Pefhany
     
  5. JMK

    JMK Guest

    --
    jan piste kronlund at tuubi1 piste net
    Please notice my new address!
    Osoitteeni on muuttunut, oikea on yllä.
    Just a little correction, Polar is Finnish company www.polar.fi ;-)

    Jan
     
  6. Fred Bloggs

    Fred Bloggs Guest

    The battery in the wrist watch is a consumer changeout, but the
    transmitter must be returned to the service center when the battery
    dies- every two-three years or so- it is a sealed unit.
     
  7. Fred Bloggs

    Fred Bloggs Guest

    The range is only slightly more than arms length because it is designed
    to be used in a group setting where several people can use them without
    interference- and this works *well*. The receiver is locking to a
    transmitter rate in addition to just simple detection so there is
    selectivity not only on signal frequency but also by steady heart rate.
    The transmitter requires a moisture layer between the skin and strap for
    best sensitivity- so if you're just sitting there in your Lazy-Boy
    versus getting off your ass and sweating, then the Polar is not for you.
     
  8. Dave

    Dave Guest

    Could you post some details?

    Thanks,
    Dave
     
  9. Dave

    Dave Guest

    I'd like to see a consumer of a S410 change the battery. It is a bitch
    and is a testament to cheap shit/unobtainable customer service.

    Polar is cheap crap, with .009mm AL metal type battery cage and soft
    plastic, coupled with nessicity for complete dissasembly - separation of
    LCD panel from PCB! Short battery life.

    I would have paid hundreds of dollars for the 6 month battery life of
    this POS, if I didn't have the nuts to change it myself 4 times. In two
    years. The plastic tabs that hold the battery are wearing out. Short
    battery life + expensive HRM + needing to line up the 20+ graphite pads
    on the display to the PCB = **** you polar.

    A $12 Chinese Timex is a bargain (battery changing wise) compared to the
    this abomination.

    Shop around.

    Venting, thanks!

    Dave
     
  10. Thot

    Thot Guest

    Hello,
    I am very interest myslef in being able to log and analyze in a computer
    overnight heart rates with the Poalr chest band or other systems.

    can you post more details?

    Thanks

    Luca
     
  11. I've been thinking of something similar and bought a cheap (Aldi)
    HRM to experiment with. This uses a similar method to the (uncoded)
    Polar units, in this case a 5.3kHz burst. Seems to be close enough
    to work with standard gym machines.

    If you google back through the sci.electronics newsgroups you'll
    find a few comments about the Polar units - the reciever apparently
    uses a Neosid encapsulated inductor as the receive coil.

    Given the audio frequency, it seems to me that a very cheap logger
    could be built by constructing a circuit built around an open-cored
    inductor and tuned to about 5kHz. Such a circuit will show 5kHz
    pulses even on an insensitive scope if held close to the HRM band.
    Add, perhaps, a little more filtering and a microphone preamp and
    then send the resulting signal to an audio recorder - one of the
    tiny flash-based music players with a microphone socket would be
    convenient, but experiments could be done with a PC sound card.

    Finally, extract the 5kHz pulses from the recorded data file
    using software on the PC. I don't know what effect compression
    will have on the recording, but it would be easy to generate
    a test file without building any hardware at all.

    -adrian
     
  12. Dan Major

    Dan Major Guest

    I used the Polar chest band, and connected to the two snaps. The EKG amp
    was a simple insrumentation amp, actually a free sample from Analog
    Devices. There are a number of such devices on the market today. I *did*
    have to add a ground reference electrode, just a disposable EKG electrode.
    The output of the amp gated a 555 on the qrs. The 555 was hooked up to an
    RF module from Radio Shack. The RF tx/rx set is no longer sold, however
    there are plenty of similar products from Linx, Abacom, etc. For the
    receiver I used a simple dipole or yagi antenna, depending on range needed,
    with the output going to a 567 tone decoder. Battery power was two 9v. If
    you bought everything new, it should cost less than $50.
     
  13. Lord Garth

    Lord Garth Guest

    That Polar unit was affecting the resistance setting on the treadmill I was
    running
    on. The thin person on the next machine was using a low resistance
    appropriate
    for her height, weight and age...when she got next to mine, all my setting
    changed
    when "my heart rate" dropped and my machine adjusted for my low heart rate!

    I set it to manual and finished the 5 miles.
     
  14. gwhite

    gwhite Guest

    I won't buy a Polar because I don't want to send the chest strap in to get the
    battery replaced. I bought a Nashbar HR monitor for $35 and I replace the
    batteries myself. Perfect. At $35 bucks it is nearly throwaway.

    To be a little fair, hapless assemblers can screw up cheststrap seals, and sweat
    then destroys the transmitter. It has happened and I suspect this is why Polar
    does things the way they do.
     
  15. Rick Moll

    Rick Moll Guest

    You might find this helpful:

    http://rick.mollprojects.com/hrm/index.html

    I'm sure the design could be improved, but it's worked for me; and at
    least a few others have built working copies.

    Rick Moll
     
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