hello ! did anyone ever tried to use a pulse sensor (like the one sold on sparkfun) on other body part, like an arm or on the thigh? also, how accurate are this sensors at detecting a pulse?
It is usual to post a link when referring to products rather than expecting us to google search and guess at the version you have.
An IR pulse sensor works by the reflection of IR light from the bone. The finger has bone close to the surface which is why it works so well. The toes can also be used for this.
You can use the transmission by placing the emitter and sensor ether side of the ear lobe but the results are not so good.
how accurate are this sensors at detecting a pulse
Accurate is the wrong word here, it detects a pulse so it is 100% accurate. You might mean sensitive or reliable but not accurate.
My treadmill has a heart rate sensor that works on either a finger or an ear lobe.
The reason i didn't post a link is because i don't have a specific sensor, the purpose of this post is to consult what sensor i need to buy, and because its for a project with a tight budget (i'm a bio-medical engineering student) i cant just buy them all and compare them. how does it work on the ear lobe, where there is no bone? also i know there are pulse sensor that don't use a photodetector, but uses electrodes to sense a pulse (like the one you have on polar watches), do anyone know if there is an adruino version for this kind of sensors?
how does it work on the ear lobe, where there is no bone?
The emitter is on one side and the detector on the other. So the system measures the transparency which changes with blood flow. The bone reflects the IR light so the sensor and the emitter can be on the same side.
do anyone know if there is an adruino version for this kind of sensors?
I know how ECG work, and i cant use its data at my project. and about the pulse sensor - all of the sensors i seen have the emitter and the detector on the same side, and still it can sense a pulse from an ear lobe, but i think i dont have any other choice but to buy the sensor and to try it out. Ant that leads me to my final question - where to buy the sensor? i saw that sparkfun sell this sensor for 25$, but you can find on ebay pulse sensors that look exactly the same but at a fraction of the price (like this one or this one) . did anyone have any experience with buying this sensor from ebay (or anywhere else beside sparkfun) ?
I know how ECG work,
Then why did you say:-
i know there are pulse sensor that don’t use a photodetector, but uses electrodes to sense a pulse (like the one you have on polar watches), do anyone know if there is an adruino version for this kind of sensors?
and i cant use its data at my project.
all of the sensors i seen have the emitter and the detector on the same side,
Do you think you have seen everything.
The ear lobe sensor could have a reflector on the other side, like a piece of foil.
Attached is a circuit I published in 1984 that uses an IR emitter and detector.
If you have ever been in hospital, you will have had “obs” done. A finger sensor like a clothes peg looks at the transmission or possibly reflection of red light through the capillaries to a photo detector generally on the opposite side to the transmitter. Not only does it do pulse, but O2 saturation as well. There might be transmission and reflection light sensors. For a bio-medical aspiring engineer, you need to do some homework. Having been on the wrong side of A&E doors, I can assure you that pulses are never taken by instrumentation on thighs or upper arms using optical methods - upper arm pulse methods use cuffs and sphygnomanometers to get pulse and BP.
An ultra-bright red LED and a TSL261 (can’t remember the exact part number) with finger in between plus a scope works well. Then it’s up to you to discriminate the pulse from the noise. I thought engineering was all about finding new solutions, not going over some very old ground. Ebay is not a good place to make medical breakthoughs with - a better bet are sites like Texas Instruments who do a vast range of bio-medical sensors. Yes, you do need to buy a few bits and try things out, it’s what it’s all about
Oh, and, some of the spelling and grammar in this posting leave a lot to be desired, just an “ob”