Go Down

Topic: Pulse heart sensor? (Read 2 times) previous topic - next topic

cyrano

I tried making something like that work, years ago. The IR solution didn't work for me, probably because of the noise level in the preamp.

Finally, I used a small loudspeaker, directly attached to the torso. That proved much easier to filter/amplify and worked very well. The speaker cone was filled with polystyrene, in order to provide a flat surface.

Not sure this will do in your case, but hey, you never know...


Daniel

Hi

i actually tried to do this a few years ago. The threads above are correct in that the pulse oximeter is the way to go. You can get a box of them on Ebay: they have a proprietary connector that gives you access to the led and a phototransistor.

Now the bad news:

1. You need some pretty sweet, very low noise operational amplifiers to detect the change in the phototransistor. If I remember correctly, a heartbeat caused a 10mv change in the photosensor's value.

2. These pulse oximieters are designed largely for people who are lying in bed and not moving around much! Every time you move your arm around, the blood gets sloshed around in your arm, and influences the signal coming from the phototransistor. Add that blood-sloshing-noise to your 10mv change detector above, and you have got a pretty serious analog and digital  job on your hands. The computerized circuitry that detects the light change in the commercial oximeters filters out such movement anomalies... so you will have to figure out how to do this in yours.  Headache number two.

I never really got it working the way it was supposed to... but if you can, I want the schematic! :)


chris


Ok this home made solution isn't going very far.

I have found this for £20 though
http://www.relax-uk.com/product.asp?id=13&sm=14
http://www.bio-medical.com/product_info.cfm?inventory__imodel=6002F

It comes with USB Mini B though, which won't go into a PC and don't think a converter will help.

They say you need this USB Pod for $185
http://www.heartmathstore.com/cgi-bin/category.cgi?item=6002-H&type=store


aalex

Hi !
I want to do the same thing.

Maybe a LED and a light sensor. (with a voltage divider) Also, we could use a sound sensor like on this page :

http://www.doctronics.co.uk/voltage.htm

Then, we would need to measure the analog in over time, and record peaks frequency using something like the Metro library. http://www.arduino.cc/playground/Code/Metro

Alexandre Quessy

chris

Sorry I am being a complete tool, skimming rather than reading properly.

My main problem is lack of circuit diagram knowledge, knowing what components are needed for amplifier circuit & how to wire them up. About time I learnt.

Go Up