Wireless Heart Rate Monitor

Hi,

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

Thanks, Mark

Reply to
Mark Witczak
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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

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Reply to
Spehro Pefhany

Are you talking MICS (Medical Implant Communications Service)?

Reply to
Thomas Magma

Mark Witczak wrote in news:nCwQd.36312$Vg3.2296 @lakeread05:

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.

Reply to
Dan Major
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Reply to
JMK

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.

Reply to
Fred Bloggs

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.

Reply to
Fred Bloggs

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

Reply to
Thot

Dan Major wrote in news:Xns95FEC23895A26soonerboomergbronlin@68.12.19.6:

Could you post some details?

Thanks, Dave

Reply to
Dave

Fred Bloggs wrote in news:421339E8.3050102 @nospam.com:

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 = f*ck you polar.

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

Shop around.

Venting, thanks!

Dave

Reply to
Dave

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

Reply to
Adrian Godwin

"Thot" wrote in news:VDUQd.80789$bu.11978@fed1read06:

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.

Reply to
Dan Major

computer

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.

Reply to
Lord Garth

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.

Reply to
gwhite

You might find this helpful:

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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

Reply to
Rick Moll

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