Using Arduino to measure heart rate using LED and photodiode pair

Hello, I am helping a friend build a "photoplethysmograph" ( a device which will tell the heart rate of someone by attaching a pair of LED and a photodiode ).

I am trying to work out a software algorithm for it but my friend has a shortage of time, so I thought about posting it here also, so that if any body has made something like this before or can guide me the process will take much less time.

This is what I am planning to do.

Connect a photodiode and IR LED in proximity but insulated from each others so that when I put my fingertip on the LED and detector pair, the detector will recieve variable amount of light depending on the heartbeat pulse.(I think I am not being very clear, Take a look here:

Now, what I think I will do is, get that signal, filter and amplify it to get a series of pulses that will correspond to the heartbeat. But how do I count those pulses? This is a part where I am a little confused. I am trying to find a way but if anybody can guide me it will be great. :slight_smile:

I've never done anything like this but it does not seem to hard,
you would have to tweak with the brightness of the led so it does not wash out thd reciever
The reciever would probably need to be hooked up to an analog input to read different levels of light,
you would have to make a program that reads the sensor semi fast in order to record the min and max of brightness received over time. You would need some programming to detect the level of brightness that is sufficiently high enough to signify a peak. Then you should be able to countthe number of peaks per second and translate into a heart rate,
The programming will be a big hard but possible

Thanks for your inputs. I am working on it. Hopefully I will be able to tackle the programming part. :slight_smile:

I wrote an article about this way back in 1984, some one put it on line:-


Many many thanks to you :):slight_smile:

@mohitdaksh I was wondering if you were able to complete this project, I am trying to measure the heart rate as well, the same you did, I was wondering if you will be willing to share what you did, thank you so much!

Sorry for late response.. But I was unable to complete it

I wrote an article about this way back in 1984, some one put it on line:-

Two things I never though I'd see again were Jimmy Hoffa and source code in BASIC!

anyhow, congrats on the article. Considering it was written in 1984, it was a breakthrough for the time.

I'm attempting to start a project for a grad course I'm taking. I'm interested in doing something similar to this, only not using but not using lights and photodiodes. I want to use the Lilypad device in an attempt to make a heart rate monitor for my dog. After a lot of searching, I couldn't find anything... So I figured I'd ask. Thanks for any help!