Help me please.........Very important question for me

[installer2001]

hello Guys,
plz help me urgently


Query is that "How IR can pass through Human finger or Ear Lobe "


Suppose that we have IR transmitter & receiver .

(IR TRANSMITTER) then i place my finger (or ear lobe) in between and then i place IR receiver .
So none of the light is able to pass through my finger(or ear lobe) and the receiver is in cutoff bcoz no IR pass through from my finger (or ear lobe) .

Sir plz tell me any IR transmitter that will able to penetrate the human ear lobe.
bcoz ear lobe is most sensitive part of human body without any bone
Is there any higher intensity IR available ,if yes then from where.
Sir if at output i get only few millivolts then it will be more than enough for me....

I am currently using LED55(IR transmitter working at 940nm wavelength ) but not getting desired result .

 

[AndyECE]

Your skin (water, etc) is a strong absober of IR radiation. It will penetrate extremely poorly.

I imagine that the signal that you try to use will be overpowered by the natural IR radiation that your body is emiting on its own.

 

[installer2001]

Sir then what i have to do to increase my power output.........

Please please think on this and reply as soon as possible...

 

[Meridian]

Sir then what i have to do to increase my power output.........

Please please think on this and reply as soon as possible...

Why is that... homework???

 

[installer2001]

respected Meridian
It's not my homework...It's my project .
I am designing some Biomedical relatd project....

 

[jdtoronto]

It is actually more common to use RED leds for that sort of use rather than infra-red. Often the led is driven with a modulating AC source and then this is demodulated on the receiving side to remove ambient lighting artifact.

John

 

[pauloynski]

For sure the human body will absorb allmost all IR radiation but this kind of circuit has been widely used. However, red leds seem to be less absorbed. To make a test place a red led behind your ear lobe and you´ll see it clearly (obviously you can´t compare it with an IR). The key is to use a very high intensity light emitter. In a conventional light receiver you´ll have as an output a DC level, lots of noise and a varying signal correspondent to the variation of the blood pressure. Take a look at this **broken link removed** and this http://www.8051projects.net/_IR_based_heart_beat_sensor. The idea of AC modulating the signal is very interesting because it will help removing unwanted signals and easy filtering. Please google for "heart beat monitor" and you´ll find some circuits (including in this forum) or like this **broken link removed**.

 

[Raidar]

Have you tried RF Exposure research on human body and perhaps you can see the effects of IR on human body too..The power around 4 dB

 

[nikhilele]

give a try to blue leds.

 

[Audioguru]

This project is discussed on another website.
Google was used to find many similar projects that shine near-infrared (does not respond to heat) through earlobes and fingers.

The OP posted the datasheet for his near-IR LED that has a peak current rating of 10A!

He was asked to post his schematics but none has appeared. His last post indicated that his IR receiver circuit was just a light-dependent-resistor so no wonder it does not work.

 

[installer2001]

Kindly help me in selecting appropriate receiver for my circuit. instead of LDR.. and also discuss it's circuitry..

whether i should use IR receiver IC or an IR photo-diode with a preamp or an IR photo-transistor??

 

[Audioguru]

I think you should do your own research. Then you will learn.
Maybe you should just copy one of the similar projects on the internet.

 

[vistapoint]

There are numerous circuits that can be found with google. The IR signals after the finger or ear lobe is still pretty strong, not a challenging design.

You dont' even need laser diode or special detectors. PIN detectors will be fine. Try google oximeter IR diodes or something.

__________________________________________
low price 1/4W 1% resistors on ebay:
**broken link removed**

 

[mosfets.bjt]

what can i tell u is,
ir is extremely low frequency light.
penetration of ur light or radiation depends on ur frequency,
as frequency increases, penetration increases,
thats why ur ir cannot pass thorugh human body but ur mobile signals can pass all the walls of ur house and u r connected with world.

regards
mosfets.bjt

 

[INS-ANI]

@mosfet.bjt
what is the max thickness ir can penetrate?
i am considering wood and plastics in my case.

 

[mosfets.bjt]

only transparent objects will let ir pass through.
you can also use translucent object of very low thick ness...

instead of having a long discussion, just take any night vision handycam or mobile camera,,, turn on ur infra red.... see the infra led through ur camera... u will be able to see its light....

just place an object b/w camera and infra led to abserve. if u can see the light through object, u can use that object, otherwise not.

 

[gulabsingh]

this application note by texas instruments will give you all the answers of your questions...