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UART transmission using IR photo diode

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MUKESH.K.S

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I am planning to try UART transmission using IR photodiode instead of TSOP. But the problem is that the photodiode is affected by sunlight. How can i solve these problems. Any body have tried this before ? I want your valuable suggections
 

KlausST

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Hi,
Any body have tried this before ?

==> look for IRDA.


Klaus

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Hi again,

in another thread you answer this:
You have to learn PIC UART communication and IR sensor TSOP1738. Modulate serial data with 38khz signal(can be generated by pwm in pic) and send to IR led. The tsop will do the demodulation and gives back the serial data. Google it you will get lot of examples.

==> The 38kHz modulation is especially made to solve the sunlight problem.

Klaus
 

MUKESH.K.S

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Thank you for replying me. I am struggling with the bandpass filter design that I have to use with the IR diode. The tsop sensor itself contains the 38khz filter.
Whats the better method for it ?
 

KlausST

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Hi,

why bandpass?

* IRDA doesn´t need it. It is not modulated.
* TSOP1738 has built in filter
* Build your own receiver ciruit (does this make sense?) -->
you need to suppress DC caused by sunlight. Ok, indeed is about 0.0000116 Hz, with a lot of noise ;-)
and you need to pass 38kHz, but with low group delay to meet the baud rate.

all in all I think a receiver with built in filter (and AGC and demodulator) is reliable and cheap...
(At least I don´t want to design, calculate and test this all.)
Looking at Farnell gives 100 pieces of IR receiver with 38kHz filter. Starting below 0.50€ for a single piece

Klaus
 

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