TV remote IR receiver module
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From: Hammy on 26 Nov 2009 18:35 On Thu, 26 Nov 2009 23:01:02 +0530, "pawihte" <pawihte(a)invalid.com> wrote: >Hammy wrote: >> On Thu, 26 Nov 2009 13:00:33 +0530, "pawihte" >> <pawihte(a)invalid.com> >> wrote: >> >>> Are TV IR remote control receiver modules frequency selective? >>> I >>> know that remote control systems use PWM and the pulses are >>> decoded by a microprocessor. What I would like to know is >>> whether >>> the module that functions as the IR photosensor, amplifier and >>> pulse shaper is usually tuned to a particular carrier >>> frequency >>> so that they are not all interchangeable (aside from things >>> like >>> pin-out, pulse polarity, etc.). >>> >>> If this is so, how sharply are they tuned? Is it likely that a >>> receiver tuned to, say 38 kHz, will respond well to 36 or 40 >>> kHz >>> emissions? >>> >> They have an integrated band pass filter with a narrow >> passband. Here >> is a picture of a Panasonic detectors sensitivity versus fc. >> >> http://i50.tinypic.com/zn4u4h.png >> >> It may work but at a minimum you will have a reduced range. >> Sensitivity for the 38kHz Panasonic is reduced to about 54% >> typical at >> 36kHz. >> >> Other things to consider is they are also matched to specific >> wavelengths which is what the other graph shows. > >Thanks. This one appears to be intended for 940nm LEDs, with >practically zero response to 850nm radiation. Are remote controls >more or less standardised for 940nm? Not sure but likely considering the availability of universal remotes. >> They also have >> specific data formats here's some from the TSOP348XX series. >> >> >> The data signal should fulfill the following conditions: >> o Carrier frequency should be close to center frequency >> of the bandpass (e.g. 38 kHz). >> o Burst length should be 10 cycles/burst or longer. >> o After each burst which is between 10 cycles and 70 >> cycles a gap time of at least 14 cycles is necessary. >> o For each burst which is longer than 1.8 ms a corresponding >> gap time is necessary at some time in the >> data stream. This gap time should be at least 4 times >> longer than the burst. >> o Up to 800 short bursts per second can be received >> continuously. >> >This seems to imply that it's not suitable for detection of a >continuous emission with infrequent interruptions for >applications like an intrusion detector or an event counter. Is >that correct? If the intruder is the "Flash" then it wouldn't be suitable for intrusion detection. The carrier is usually modulated (On/off) at about 1 kHz (1mS). They are indeed used for this application I've done it and you will find lots of examples on Google. here's a link showing the carrier and data waveforms etc. http://www.rentron.com/Infrared_Communication.htm For an intrusion detection application you usually would not trip your alarm unless you had a loss of signal longer then 100ms no human being can run through a detector at that speed. This helps to avoid nuisance trips. A dual or multiple beam is even more reliable and less prone to nuisance trips i.e cat, dog or leaf etc. Alignment could be difficult and flooding adjacent receivers could be problamatic witout optics to narrow the beam. >> It doesnt hurt to try if your just scavenging detectors and >> emitters. >
From: pawihte on 27 Nov 2009 02:32 Hammy wrote: > On Thu, 26 Nov 2009 23:01:02 +0530, "pawihte" > <pawihte(a)invalid.com> > wrote: > >> Hammy wrote: > >>> They also have >>> specific data formats here's some from the TSOP348XX series. >>> >>> >>> The data signal should fulfill the following conditions: >>> o Carrier frequency should be close to center frequency >>> of the bandpass (e.g. 38 kHz). >>> o Burst length should be 10 cycles/burst or longer. >>> o After each burst which is between 10 cycles and 70 >>> cycles a gap time of at least 14 cycles is necessary. >>> o For each burst which is longer than 1.8 ms a corresponding >>> gap time is necessary at some time in the >>> data stream. This gap time should be at least 4 times >>> longer than the burst. >>> o Up to 800 short bursts per second can be received >>> continuously. >>> >> This seems to imply that it's not suitable for detection of a >> continuous emission with infrequent interruptions for >> applications like an intrusion detector or an event counter. >> Is >> that correct? > > If the intruder is the "Flash" then it wouldn't be suitable for > intrusion detection. The carrier is usually modulated (On/off) > at > about 1 kHz (1mS). They are indeed used for this application > I've done > it and you will find lots of examples on Google. > > here's a link showing the carrier and data waveforms etc. > > http://www.rentron.com/Infrared_Communication.htm > > For an intrusion detection application you usually would not > trip your > alarm unless you had a loss of signal longer then 100ms no > human being > can run through a detector at that speed. This helps to avoid > nuisance > trips. > > A dual or multiple beam is even more reliable and less prone to > nuisance trips i.e cat, dog or leaf etc. Alignment could be > difficult > and flooding adjacent receivers could be problamatic witout > optics to > narrow the beam. > I'm not really trying to build an intrusion alarm. I'm trying to learn more about the practical espects of IR remote control design. The inrusion alarm was just an example of a possible application, but it seems the Vishay TSOP348XX receivers are designed on purpose to reject CW signals. The Panasonic PNA4602M datasheet doesn't say anything specific about this.
From: pawihte on 27 Nov 2009 07:51
pawihte wrote: > > I'm not really trying to build an intrusion alarm. I'm trying > to > learn more about the practical espects of IR remote control > design. The inrusion alarm was just an example of a possible > application, but it seems the Vishay TSOP348XX receivers are > designed on purpose to reject CW signals. The Panasonic > PNA4602M > datasheet doesn't say anything specific about this. A Silan SM0038 module is very common in my area, being available at practically all parts shops, but I can't find a datasheet for it. Silan is a Chinese company and the type number probably means it's tuned to 38kHz. It works at 5V. What's unknown is the spectral range and whether it has restrictions regarding burst length and duty cycle as with the TSOP348xx. I've emailed the company, but no reply yet. Can anyone help? |