Of all the body responses one could monitor, heart rate is one of the most important because it fluctuates greatly depending on our state of mind and physical condition. Heart rate during physical activity gives us a direct indication of our fitness level, and heart rate changes throughout the night can be clear indicators of when a dream cycle has begun. A heart rate monitor is also a very easy device to use for extended periods because it can
be placed on the body in such a way that is not uncomfortable or in the way of any normal activity.

The heart rate monitor project presented here uses a sensitive light-detecting resistor to detect small changes in the light beaming through your finger as your blood pumps through the tiny arteries in the finger. This device is not the same as the heart rate monitors typically used in hospitals because those use skin probes that detect changes in electrical activity as the heart beats. This heart rate monitor actually “sees” your pulse through the body, so it can be used on a finger, toe, or even your earlobe.

The heart rate monitor is a combination of analog and digital circuitry, as shown below.



The LM324 quad op amp (IC1) forms a sensitive amplifier and a low-pass filter that will “lock” onto tiny variations in voltage that fall within the typical heart rate frequencies. The varying voltage comes from the light-dependent resistor (LDR), which changes a very small amount each time blood pumps through the tiny arteries in between the visible red LED and the LDR surface.




Complete Design



Insert Your Fingure Here







if you feel any doubt or need further details feel free to use Forum.
Source: Evil Genius MPP Issue 2010
[Submitted by coolmirza143]
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Sun May 24 2015, 06:51 AM
Subrat Sahu
I have a confusion about 10 bit adc formula as describe bellow that resolution = Vref/1023 or Vref / 1024
Sun May 24 2015, 06:49 AM
Subrat Sahu
I have a confusion about 10 bit adc formula as describe bellow,
ExperimenterUK
Sat May 23 2015, 08:54 PM
@utpal.. Create a thread in the Pic forum
Thu May 21 2015, 01:04 AM
utpal
i am a hobbist. i work on 8051. just i have started with pic 16f877. but a bitter experiance is going on. as i am programming any code to my pic877 and putting it in my board and it is working, but the 2nd time it is not taking any program,I have experimented just 7 new one pic mcus. result is the same. please tell me the reason. my programmer is TOP3000(universal programmer).
ajay_bhargav
Wed May 20 2015, 04:48 AM
@lak you can use the same code provided you are not using any s52 specific ports and registers.
Mon May 18 2015, 05:58 AM
lak
i used to develop a code for at89s52 shall i use the same code for at89c4051
Sun May 17 2015, 07:57 AM
Ayoosh
what if i have to rotate motor continuously at a step angle of 1.8 degree
ExperimenterUK
Fri May 15 2015, 06:02 PM
@oracle1946.. Post your question in the PIC forum
Fri May 15 2015, 03:48 AM
nadeem232
if some has solution kindly share solution Principles of Electric Circuits,by Thomas L. Floyd
oracle1946
Thu May 14 2015, 03:39 PM
I want to build a PIC16F684 sun logger using either a solar cell (0.5v solar cell or photoresistor). Any help out there?

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MuhammadTanvir
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Posted By MuhammadTanvir
Sun May 24 2015, 11:11 AM
Hey guys !! Can somebody please share the proteus ...
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Posted By MuhammadTanvir
Sun May 24 2015, 11:07 AM
Hey guys !! Can somebody please share the proteus ...
ExperimenterUK Avatar
Posted By ExperimenterUK
Sat May 23 2015, 09:52 PM
Does the speaker work?.'Exactly' where on the boa...
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Posted By ExperimenterUK
Sat May 23 2015, 09:44 PM
For all your questions there is a proper, very tec...
mayank058 Avatar
Posted By mayank058
Thu May 21 2015, 04:46 AM
dear sir there is nothing to zip.I just...
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Posted By ajay_bhargav
Wed May 20 2015, 04:57 AM
can you zip your complete project and attach it he...
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Posted By ajay_bhargav
Wed May 20 2015, 04:46 AM
If you know how to drive 7-seg using an 8-bit port...
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Posted By ajay_bhargav
Wed May 20 2015, 04:42 AM
There was no proteus file included in the package,...
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Posted By ankitbajaj01
Tue May 19 2015, 07:00 AM
Hello ExperimenterUK...Please guide me on above po...
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Posted By mayank058
Tue May 19 2015, 04:54 AM
Sir I want to measure the analog signal on CRO.