There are many ways to detect a heartbeat electronically. One of the simpler ways is to take [Orlando’s] approach. He’s built a finger-mounted pulse detector using a few simple components and an Arduino.
This circuit uses a method known as photoplethysmography. As blood is pumped through your body, the volume of blood in your extremities increases and decreases with each heartbeat. This method uses a light source and a detector to determine changes in the amount of blood in your extremities. In this case, [Orlando] is using the finger.
[Orlando] built a finger cuff containing an infrared LED and a photodiode. These components reside on opposite sides of the finger. The IR LED shines light through the finger while the photodiode detects it on the other side. The photodiode detects changes in the amount of light as blood pumps in and out of the finger.
The sensor is hooked up to an op amp circuit in order to convert the varying current into a varying voltage. The signal is then filtered and amplified. An Arduino detects the voltage changes and transmits the information to a computer via serial. [Orlando] has written both a LabVIEW program as well as a Processing program to plot the data as a waveform. If you’d rather ditch the PC altogether, you might want to check out this standalone heartbeat sensor instead.
Pedantic correction: I think that’s pulse rate and not heart rate. They’re normally correlated but certain heart conditions can cause deviations.
If anyone is wondering what “the line” is for the amount of pedantry we allow in the comments is, there ya go.
you sure it’s a line??
Not a grey area??
If it’s a line, what thickness???
I was just looking into these things. I found the SMS BioSport In-Ear Headphones, which just plug into your phone and allow apps like Runkeeper to measure your heart rate. I believe they do this by measuring the pressure created in your ear by your moving eardrum. Seeing as it just plugs into your phone and doesn’t need any batteries or other extra power source, I wonder if it would be possible to take a project like this one, and generate the needed signal.
I’d really like to do this; anyone any idea as to what kind of signal they might generate? I guess it’s something on the line that is normally used by those push buttons you use to change volume / skip songs on certain headphones?
This project seems similar to the Pulse Sensor that was funded through Kickstarter a while back:
https://www.kickstarter.com/projects/1342192419/pulse-sensor-an-open-source-heart-rate-sensor-that/posts?_=1421009551355&page=2
So most any (at least that I am aware of) pulse sensor uses some sort of optical detection method (there are also electrical detection method). I looked into the SMS BioSport device and it does this as well. I found this on their website. “Merging premier sound quality with the latest in fitness-monitoring biometrics technology, the headphones include built-in optical sensor that continuously measures your heart rate while dynamically removing noise signals caused by your body’s motion during your workout.” http://smsaudio.com/products/biosport-in-ear-wired-with-heart-monitor
I’m not entirely sure what you are specifically referring to here, “…I wonder if it would be possible to take a project like this one [which project, the one featured by Hackaday or the headphones?], and generate the needed signal [is this ‘signal’ referring to the pulse signal in general or the signal generated by the SMS BioSport device?].”
Sorry for being unclear. What I meant was building your own pulse sensor (like the one from this post, or getting the ready to use arduino pulse sensor from the kickstarter link) and using it to create the signal used by apps like Runkeeper as a cheap alternative to the 150+ USD SMS biofit headphones.
Somehow these SMS biofit headphones manage to get extra power from the headphone jack so they can run without batteries (also means they don’t work with all phones, but it is supported by the nexus 5 I have so I don’t mind ;) )
There’s an app for that…
https://play.google.com/store/apps/details?id=si.modula.android.instantheartrate
For sure, heart monitoring is pretty standard these days. This project was done as a part of an introduction to engineering module for freshman biomedical engineering majors. It was designed to show them how simple it is to sense something like heart rate and give them the confidence to do something like that themselves. In this same lab activity, they were asked to research other devices for measuring heart rate, and compare what they did in lab, to whatever commercial product or app they could find. It was a fun class.