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Topic: Heart rate monitor (Read 2287 times) previous topic - next topic


As a small project, I wanted to try to get my pulse read by my arduino. I have tried use LDRs with superbright LEDs, but it seems that many of the existing projects use IR leds. I do have an IR led, but not a detector... the LDRs I have only "see" visible light. I also tried using an op-amp to amplify my heart's voltage, but this didn't seem to work (I also kept getting mains 60Hz interference). I'm also not sure how I should set up the op amp. Differential amplifier? Inverting amplifier? I think I'll get something like this or this, but for now, does anybody have any ideas? I have is two LM358s, some LEDs (including an LDR), an assorment of resistors, and some other general components.

Jack Christensen

Don't know anything about these, pretty spendy, but I do use a Polar monitor and they work well.

Less for just the module


I saw that... but I (1) don't have a heart strap and (2) would like to make my own.


it works really fine



I know, but I don't have the strap.


Sep 17, 2011, 08:36 pm Last Edit: Sep 17, 2011, 08:41 pm by sync Reason: 1

I know, but I don't have the strap.

The strap "T31" cost only ~20$ at any Healt/sport boutique near you. It is good for two years if used at average one hour a day.


But I wanted to make something... anyone know how that strap works?


IR led and detector is the way to go; I think that's how the belt works
there are only 10 types of people
them that understands binary
and them that doesn't

Jack Christensen

But I wanted to make something... anyone know how that strap works?

It has a two fairly large pads (~ 3" x 0.6") that pick up the electrical signals like an EKG (definitely not optical). Doesn't always work well on dry skin. Instructions recommend using a little water if you don't want to wait until you start sweating enough, and that's what I do. Once there's enough moisture they seem pretty solid. They can also be used swimming but I haven't actually tried that. Some exercise equipment has built-in Polar receivers so they can display heart rate.


I also kept getting mains 60Hz interference

Can you post your schematic?

If you use a power supply => you might add some capacitors to straighten the power signal.
Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)


You really want to check this out: http://www.kickstarter.com/projects/1342192419/pulse-sensor-an-open-source-heart-rate-sensor-that

It uses an IR Led and check for the reflection. You can probably build one yourself or buy the kit (support on Kickstarter).
Hope this helps.


How about Heart rate + midi
From 2008: http://www.flickr.com/photos/recotana/2283848566/in/photostream/



As mentioned in the OP, I wanted to use IR LEDs (hospitals use it... so it must be good!) but I don't have any photodiodes. I'll place an order for some. I guess EKG is not really the way to go....



You could try using an LED as the sensor. Yes LEDs can be input devices.
I've used an LED as an input on projects to detect light levels to detect day/night
or even when a finger is touching it.

You can hook one up across an Arduino analog input and ground
to see how the the analog input readings vary as the light varies.

The color of the LED affects the spectrum of light the LED is sensitive to
when used as a sensor. i.e an infrared led will be most sensitive to infrared light.

Google around you will find many links on how to use them as sensors
and some very impressive uses since depending on your circuitry
you can actually use the same LED for output and input.

--- bill

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