Matrix user forums

Hi all, I have been searching all the threads here but now I am completely baffled. I am making a pulse rate monitor for a project, using PIC16F88 as microcontroller and an 8bit LCD display. Could I please have some input on what is the best way to go about this. I have came across codes on this forum, however they do not seem to work for me please help

Hello,

A simple way to measure a pulse is with a LED and a LDR (Light Dependant Resistor).

The LED shines a light onto and through your finger and the LDR will provide a signal with the light intensity coming through the finger which will vary with blood flow and give you a pulse.

You then take the readings by sampling the LDR using a ADC component and a potential divider with the LDR on one side of the divider.

LDRs generally contain lead so they are becoming harder to get hold of there days, photo transistors work equally well but the current has to be tiny. For the sensor we use on E-blocks we have to use a potential divider resistor of 1MOhm.

This web page looks good at explaining the process.
http://raviyp.in/index.php/embedded/140 ... nsor-works

thanks for replying, that is the system which I am using, an LED and photodiode input. hardware is not a problem, just need the software for the microcontroller to work. any ideas?

LDRs generally contain lead so they are becoming harder to get hold of there days

I never realised that, maybe I'd better get a few in stock for future projects.

Couple of years ago I saw some Mercury tilt switches for sale at a hamfest, never seen any since. (No I didn't get any, though wish I had got a couple for historic interest).