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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Mon Nov 12 2018, 05:58 AM
Pavan_user
i have seen your replica of I2C programming using AT89C51 but i am unable to understand the "ack_bit" variable usage ...looks like it is always 1...can you elaborate how acknowledgment is working....
bgk3678
Tue Nov 06 2018, 02:36 PM
kindly any one give solution for my problem
ExperimenterUK
Mon Nov 05 2018, 09:48 PM
Pins high is the normal state. You need a program to set them low
mayengbam
Sun Nov 04 2018, 05:41 PM
hello, i am niranjoy, alll the port of my 8051 is always high, even i erase all the program. why is it so happen and what is the problem. any one please help me!
Sun Nov 04 2018, 02:16 PM
BASAVARAJ g kudamble
hi I am interfacing GSM 300 to 8051 microcontroller to receive message from mobile
ExperimenterUK
Sat Sep 29 2018, 06:28 PM
Please post questions in the forum.
Sat Sep 29 2018, 11:26 AM
Ashfaq Ch
hi i have some AT89C51RC microcontrollers already programed. some one help us to how to download from AT89C51RC and after study and edit all corractions reload to AT89C51RC controller
shshistiem
Wed Sep 12 2018, 10:58 PM
hii!! some1 please let me know how i ll get rfid code to 8051 by WEIGAND mode
DrNossberg
Tue Sep 11 2018, 08:09 PM
is there anyone here?
Mon Aug 27 2018, 07:30 AM
bun
Hello everyone!

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Unfortunately I have no experience of LabView,but ...
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Make the 8051 frequency exactly 11.0592 MHz in pro...