well we just built an ir emitter circuit emitting a 38kHz signal. we r confident that works. however the ir detector shows either high or low (when i block the signal with my hand). why does it not show a 38k signal?

help would be apreciated

 

Assuming you're using an IR receiver IC that's how it's supposed to work, it demodulates the incoming IR and 38KHz carriers, and outputs the original modulation.

However, they are designed for data, not a plain carrier, and using a plain carrier will drastically reduce range.

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we have an ic (generating the signal) hooked up to ir emitter. the receiver is just a receiver hooked up to an ociliscope

 

Like I said, it's working exactly as expected then - if you want an AC output from the receiver you need to modulate the 38KHz in the transmitter - this will also massively improve range.

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hi,
Is the ic generating the 38KHz carrier signal or is the ic modulating the 38KHz carrier and is the receiver just a detector.

That is, are the 38KHz TX and RX ready built modules or have you made them?

Do you have a diagram to post?

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Very simple concept.. it's this property helps it to use i r as proximity detector...

See.. there are two separate parameters.. 1. range 2. ability to pass through an object (transparency..)...both are independent factors...


*1. first thing you should remember is: if you want to improve the range.. then you are to reduce the duty cycle to 10 %... ( but you dont want this...)...

*2. second thing you should remember is: i am sure ..the ir rays never pass through an opaque object... Sometimes your detector gives high and sometimes low...

Reason 1 : very simple ... light travels at speed of 3,00,000Kms / sec. and hence it might be reflected many times before it reaches detector..

Reason 2 : or your detector might be faulty...


I hope you have used 555 timer...

regards..

simran...

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Simran..
8051 Specialist..

 

Use tsop 1738 as IR detector.. and that of a good quality from a german co. called VISHAY...






any help you need ask...

__________________
Simran..
8051 Specialist..

 

As Sir Nigel said, 38 kHz signal has to be modulated and and most IR receivers have a maximum of 600uS pulse width modulation, longer than this will not be received.