How do IR remote controls work so well?

[Kasterborus]

I've been experimenting with detecting reflected laser pulses in the
532nm (visible green) wavelength. By modulating the pulses and tuning
a receiving circuit I've been able to get the detector to work over a
distance of several feet in a darkened room.

I'm thinking that mixing infrared laser light with the 532nm and using
IR photodetectors. Would this allow for more ambient light in the
room?

My TV remote control seems to do very well in detecting pulses from an
IR diode, even in bright sunlight - is there more to it than just the
shift to the IR spectrum? Or is the modulation a key factor in the
detector being able to "see" the remote?

Dave

 

[[email protected]]

I've been experimenting with detecting reflected laser pulses in the
532nm (visible green) wavelength. By modulating the pulses and tuning
a receiving circuit I've been able to get the detector to work over a
distance of several feet in a darkened room.

I'm thinking that mixing infrared laser light with the 532nm and using
IR photodetectors. Would this allow for more ambient light in the
room?

My TV remote control seems to do very well in detecting pulses from an
IR diode, even in bright sunlight - is there more to it than just the
shift to the IR spectrum? Or is the modulation a key factor in the
detector being able to "see" the remote?

Dave

The modulation is a big part of it. The remotes I've worked with
(Samsung and Sony) both send 32 bits total and the last 8 bits are
sent twice, the second time inverted which helps data verification.
Both remotes continously repeat the 32 bit sequence as long as a
button is held so there's a good ghance some af the commands will get
through.

GG

 

[Bob Monsen]

I've been experimenting with detecting reflected laser pulses in the
532nm (visible green) wavelength. By modulating the pulses and tuning
a receiving circuit I've been able to get the detector to work over a
distance of several feet in a darkened room.

I'm thinking that mixing infrared laser light with the 532nm and using
IR photodetectors. Would this allow for more ambient light in the
room?

I guess it depends on the detectors. Some may filter out other frequencies.

For example, the TSOP11xx set of photo modules are very good at filtering
out light at other wavelengths. That is how IR works so well for TV, for
example; they filter everything except the 950nm IR between 900nm and 1um
down to -6db, and then only respond to modulation frequencies between 0.95
and 1.05 percent of the target modulation (ie, 40k).

See the figures in this data sheet:

http://www.tranzistoare.ro/datasheets/restul/305097_DS.pdf

My TV remote control seems to do very well in detecting pulses from an
IR diode, even in bright sunlight - is there more to it than just the
shift to the IR spectrum? Or is the modulation a key factor in the
detector being able to "see" the remote?

Dave

Again, the detector is tuned to both the frequency of light, and also to the
modulation frequency of the signal.

 

[Jamie]

I've been experimenting with detecting reflected laser pulses in the
532nm (visible green) wavelength. By modulating the pulses and tuning
a receiving circuit I've been able to get the detector to work over a
distance of several feet in a darkened room.

I'm thinking that mixing infrared laser light with the 532nm and using
IR photodetectors. Would this allow for more ambient light in the
room?

My TV remote control seems to do very well in detecting pulses from an
IR diode, even in bright sunlight - is there more to it than just the
shift to the IR spectrum? Or is the modulation a key factor in the
detector being able to "see" the remote?

Dave

They have a IR passive filter that helps reduce non IR light .
also, the modulation scheme has a lot to do with it.

Normally common mode input receivers are used with capacitor
offsets on one input so that the DC component can be nulled out
while the AC component will be visible with high gain..
they may even have a band pass filter after that stage..

This means, your modulation scheme must use a steady stream
of pulses for 1's or 0's.




http://webpages.charter.net/jamie_5"

 

[John Fields]

They have a IR passive filter that helps reduce non IR light .
also, the modulation scheme has a lot to do with it.

Normally common mode input receivers are used with capacitor
offsets on one input so that the DC component can be nulled out
while the AC component will be visible with high gain..