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ckt using LDR

hi, I'm planning to work with a simple ckt. Just have only few ideas about the ckt. following are the details:

the ckt is meant to be a, heart pulse detecting ckt. main principle: finger tip is to be placed in the gap between a LED and a LDR, so that at each time the heart pumps,the pressure at tip changes. (OR), i.e.,during respiration,while breath in , blood gets oxygenated.thus haemoglobin absorbs light from the LED and less light is sensed by the LDR.corresponding analog voltage is obtained at the output.

This output has to be converted into digital form using the A/D- convertor module of any microcontroller(amplification is required with high gain).The final output has to be displayed in the CRO.

I believe you could help me with the ckt, its a kind of urgent,(max 4 days more).

Thanks, Neona.

Reply to
itzneona
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Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com
Reply to
Tim Wescott

few

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=A0 =A0 =A0 =A0 =A0(OR),

e quoted text -

Yeah I'm assuming the LDR is light depenedent resistance.. but who knows.

What kinda LED are you going to use Neona? When I hold my finger up to the room lights not very much light get through. (You are going to have really small signals.) You might try sensing through the 'webs' between your fingers.

Do you know what wavelength(s) hemoglobin abosrbs?

and why do you want to go to all that work to make your signal digital and then display it on a CRO... (Cathode Ray oscilloscope?)

I'd first try a photodiode for sensing the light...

George H.

Reply to
George Herold

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