Electronic Components

Last week my friends and I went to Jalan Pasar to buy some electronic stuff. Pictures of component that i bought.

Proof Of Concept

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A small poc to prove that my circuit  is working and how green led will act in the realtime. Green led is going to blink  when infrared light reflected by fingertip is detected by ldr (light dependent resistor). Our heart beat is represented by the green led.

My Circuit Design

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I am using Proteus 7.7b to design and simulate the circuit diagram for my fyp project. This is the analog part of my circuit. How it works?

1. The circuit is supplied with 5 volt power supply.
2.  IR led and Green led will turn on because current will go through C1 due that ldr is made of high resistance semiconductor.
3. Put fingertips near the optical sensor, it will cause the Green Led to blink indicating our rate of heart beat.

Theories and explanation?

Heart rate is measured by sensing the change in blood volume in a finger artery  while the heart is pumping the blood. The changing blood volume with heartbeats results in a train of pulses at the output of ldr. We can simply say that if the rate of heart beat is high then the Green led will blink faster.

A Brief Introduction To My Project

I am developing an electronic gadget which monitor heart beat measurement using a low cost microcontroller. Optical sensors will measure the alteration of in blood volume at fingertip with each heartbeat.

The sensor unit consists of an infrared light-emitting-diode (IR LED) and a light dependent resistors (LDR), placed side by side. The IR diode transmits an infrared light into the fingertip (placed over the sensor unit), and the LDR senses the portion of the light that is reflected back. The intensity of reflected light depends upon the blood volume inside the fingertip. So, each heart beat slightly alters the amount of reflected infrared light that can be detected by the LDR.

With a proper signal conditioning, this little change in the amplitude of the reflected light can be converted into a pulse. The pulses can be later counted by the microcontroller to determine the heart rate.