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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ExperimenterUK
Tue Jun 30 2015, 05:24 PM
@sachinmm The 8051 timer can't do 1 second. It can do 50ms so count 20 times
sachinmm
Sat Jun 27 2015, 05:01 AM
how calculate 1 second delay in 8051 by using timer and what value should be store in TH0 & TLO register??
sachinmm
Fri Jun 26 2015, 08:25 AM
hello sir plz tell me how to know the 74HC165 parallel in serial out ic is fauty or not?
Wed Jun 24 2015, 08:24 AM
ben mutuku
How can one use XOR gate to ensure the first output is '1' and the next is '0'?
ExperimenterUK
Wed Jun 17 2015, 01:37 AM
@baz..try adding a hash and a semi colon
Sun Jun 14 2015, 06:31 AM
baz
@ExperimenterUK no..i dont do that i just type message example.. Hello my name is baz and then i click send message,
ExperimenterUK
Sun Jun 14 2015, 01:55 AM
@baz..did you end your message with a hash and a semi colon
Sat Jun 13 2015, 06:48 PM
asif Jamadar
I want the program for v/f control technique of 3 phase induction motor
Sat Jun 13 2015, 07:06 AM
baz
@ExperimenterUK okay thank you...but now I already complete and my dot matrix already light up but when i send message from pc to my hardware project it doesnt show any message on my dot matrix..its only blinking when i click send message....I really dont know whats the problem...I had follow all the steps...schematic and use the coding that have been provided..is it because firstly i had wrong burn the coding in AT24C16?? Is that effect ????
ExperimenterUK
Sat Jun 13 2015, 12:08 AM
@baz Load the hex file into the at89c52, The at24c16 holds the message to display

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@ExperimenterUKThanks a lot for correcting my misc...
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@ExperimenterUK Thank you for your simple and usef...
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The 8051 timer can't do 1 second. It can do 50ms, ...
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