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]
printer friendly create pdf of this news item

Submit comment

(Required; Min length 5)
(Required; will not be displayed)


Tue Oct 06 2015, 08:22 AM
HI you looking for ideas or you have solution
Fri Oct 02 2015, 03:39 PM
poojitha: projects on wireless communication between two microcontrollers
Thu Oct 01 2015, 04:38 PM
hey! i wanted to simulate my circit using proteus. i have a sugar cube relay in my circuit....but i dont know which one is that in the device libraries of the software. any help? thankyou.
Tue Sep 29 2015, 09:40 PM
@Michal, that rocket is too heavy for itself and trust is not enough unless afterburners are fed with fuel properly.
Sat Sep 26 2015, 08:19 PM
Hello, its possible to make a amateur rocket with this engine, or something simillar, which be able to flight?
Thu Sep 24 2015, 10:38 AM
Ir Switch sir.
Wed Sep 23 2015, 01:10 AM
@engr1931 which project ?
Tue Sep 22 2015, 11:57 AM
Hello sir, is it ok to use 12.000MHz oscillator in IRswitch, because the requirement written in the post is 11.059MHz. And i use PIC1018 as an Ir receiver
Mon Sep 21 2015, 04:15 PM
Hello sir, your blog is kind of helpful for us especially students. May I know do you have the coding for decimal to binary using proteus 8. My mini project is about to convert decimal to binary just like a calculator. The output is LCD. A bit confusing is the decimal to binary coding on proteus 8. pls help thanks.
Sun Sep 20 2015, 09:08 PM
Have you searched our Embedded GSM Development and GSM and CDMA Discussion forums ?



Tue Oct 06 2015, 01:02 PM
Fri Oct 02 2015, 03:28 PM
Sat Sep 26 2015, 01:26 AM
Fri Sep 25 2015, 10:57 AM
Wed Sep 23 2015, 08:13 PM
Wed Sep 16 2015, 04:55 AM
Mon Sep 14 2015, 03:06 PM
Fri Sep 11 2015, 06:03 AM


Guests: 28, Members: 0 ...

most ever online: 182184
(Members: , Guests: 182184) on 06 Aug 2010: 05:37 AM

Members: 37698
Newest member: praveenraoms
Forum Activity
praveenraoms Avatar
Posted By praveenraoms
Tue Oct 06 2015, 01:06 PM
hi i want to know the code to access the geographi...
sachinmm Avatar
Posted By sachinmm
Wed Sep 30 2015, 08:54 AM
how to used polling method in this?? my code is co...
ajay_bhargav Avatar
Posted By ajay_bhargav
Tue Sep 29 2015, 09:39 PM
__irq is just compiler directive to wrap IRQ routi...
ajay_bhargav Avatar
Posted By ajay_bhargav
Tue Sep 29 2015, 09:36 PM
The comment does say the time values as per the th...
ajay_bhargav Avatar
Posted By ajay_bhargav
Tue Sep 29 2015, 09:33 PM
are you testing this on Proteus? or MplabX simulat...
ajay_bhargav Avatar
Posted By ajay_bhargav
Tue Sep 29 2015, 09:31 PM
[Topic moved to ARM Development Forum]
ajay_bhargav Avatar
Posted By ajay_bhargav
Tue Sep 29 2015, 09:29 PM
start with reading datasheet. SPI interface on LPC...
ajay_bhargav Avatar
Posted By ajay_bhargav
Tue Sep 29 2015, 09:27 PM
I am not sure you've solved it or not but "USARTRe...
ExperimenterUK Avatar
Posted By ExperimenterUK
Tue Sep 29 2015, 06:31 PM
i am confused in "__irq"....how it is uesd??sachin...
sachinmm Avatar
Posted By sachinmm
Tue Sep 29 2015, 11:11 AM
my I2C.c file=>>/*********************************...