# Wireless Heart Rate Monitor

M

#### Mark Witczak

Jan 1, 1970
0
Hi,

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

Thanks,
Mark

T

#### Thomas Magma

Jan 1, 1970
0
Are you talking MICS (Medical Implant Communications Service)?

D

#### Dan Major

Jan 1, 1970
0
Hi,

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

Thanks,
Mark

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.

S

#### Spehro Pefhany

Jan 1, 1970
0
Are you talking MICS (Medical Implant Communications Service)?

Polar is (Swiss) a manufacturer of wristwatch-Heart Rate Monitors
(HRM) that are used by people working out. They have a separate
wristwatch. They're a consumer product, albeit a niche one. Their
manuals are a bit.. opaque.

Best regards,
Spehro Pefhany

J

#### JMK

Jan 1, 1970
0
--
jan piste kronlund at tuubi1 piste net
Osoitteeni on muuttunut, oikea on yllä.
Mark Witczak said:
Hi,

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

Thanks,
Mark

Just a little correction, Polar is Finnish company www.polar.fi ;-)

Jan

F

#### Fred Bloggs

Jan 1, 1970
0
Spehro said:
Polar is (Swiss) a manufacturer of wristwatch-Heart Rate Monitors
(HRM) that are used by people working out. They have a separate
wristwatch. They're a consumer product, albeit a niche one. Their
manuals are a bit.. opaque.

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.

F

#### Fred Bloggs

Jan 1, 1970
0
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.

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.

D

#### Dave

Jan 1, 1970
0
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.

Could you post some details?

Thanks,
Dave

D

#### Dave

Jan 1, 1970
0
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.

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.

L

#### Lord Garth

Jan 1, 1970
0
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.

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.

G

#### gwhite

Jan 1, 1970
0
Dave said:
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! 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.

R

#### Rick Moll

Jan 1, 1970
0
Mark said:
Hi,

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

Thanks,
Mark

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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