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


18 Oct 2012: 20:11 PM
What compiler to use to compile source code?
18 Oct 2012: 20:17 PM
Is there minimum and maximum values for value on LED ?
31 Oct 2012: 22:31 PM
You can make use of AVRstudio to assemble this code.
01 Nov 2012: 06:13 AM
can i know what type of atmega88 use in this circuit?and for the 7 segment display is common anode or common cathode?
03 Nov 2012: 00:04 AM
AVRStudio cant compile this!
03 Nov 2012: 00:38 AM
Say source is : Evil Genius MPP Issue 2010

Can someone help with some link to source?

Submit comment

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



Fri Apr 18 2014, 03:09 AM
Fri Apr 18 2014, 02:00 AM
Thu Apr 17 2014, 05:32 PM
Thu Apr 17 2014, 10:19 AM
Thu Apr 17 2014, 08:44 AM
Wed Apr 16 2014, 07:32 AM
Tue Apr 15 2014, 04:12 PM
Tue Apr 15 2014, 11:21 AM


Thu Apr 17 2014, 01:23 PM
@mba Great .. please do.
Thu Apr 17 2014, 12:27 AM
like the forum and wish to participate
Wed Apr 16 2014, 04:45 PM
@viniciusheidrun..you should read my comment just before your post
Wed Apr 16 2014, 01:43 PM
I'm doing a drive system with SIM900D modem and microcontroller AT89S52 via sms. I'm having trouble can not generate the. Hex to send to the microcontroller, whenever I compile the error, I'm using MCU 8051 IDE, what should I do so that my system receive sms and perform my task?
Mon Apr 14 2014, 01:00 PM
@Haranadh,bipin chandra etc. Create threads for your questions.
Sun Apr 13 2014, 04:05 AM
we bought HC 06 Bluetooth modem instead of Module ,Can any one help me of using it as bluetooth module since i am doing this project?
Sun Apr 13 2014, 03:58 AM
Hi,Actually we bought Bluetooth modem instead of Bluetooth Module
Sat Apr 12 2014, 02:55 PM
Please use forum if you want to ask a question.
Sat Apr 12 2014, 01:06 PM
Hi Ahana,I can Help you on this
Sat Apr 12 2014, 03:51 AM
bipin chandra
can anybody help me. we are making a project to control the position of dc motor. so there we need to interface lcd screen and the 4X3 memberane keypad and a dc motor driver chip. can anybody please give me the complete circuit diagram connection of these components with the 8051.and alse help in the programming. my email id is bipin.chandra666@gmail.com
  Choose Skin