Heart rate monitor using PIC 16f877 and output display on LCD

[Sim123]

Hello everyone!! I am designing a heart rate monitor using PIC micro controller 16f72. The input which i'll get from the heart beat sensor(IR LED and photodiode), i am using LM358 to amplify that.The output of LM358(which is opamp) will be analog. I should give this as an input to PIC microcontroller's ADC(Analog to digital converter pin). But in all the circuits available for reference it is giving to T0CLK (Timer 0). How PIC will use this analog input without analog to digital converter. Please advise!!

 

[barry]

You have threee choices:
1) Take the output of the LM358 and send it into a voltage comparator which will give you a digital signal you can apply to T0CLK
2) Write software to determine zero-crossings on the signal from the ADC and measure time between crossings
3) Use a different micro-one with a comparator built in. Many PICs have a zero-crossing detect module.

Wait, fourth choice:
Instead of using an LM358, can you use a voltage comparator?

 

[KlausST]

Hi,

maybe the LM358 is used as a comparator. --> the schematic will tell you.

Klaus

 

[Sim123]

Hi,

maybe the LM358 is used as a comparator. --> the schematic will tell you.

Klaus

Thanku so much guys for the help. I'll try to configure LM358 as a voltage comparator.