TV remote IR receiver module

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?

Reply to
pawihte
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Generally, the 3 dB down points of these are at about +/- 2 KHz so yes, you'll get a response with a 36 KHz signal using a 38 KHz module.

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Rich Webb     Norfolk, VA
Reply to
Rich Webb

They have an integrated band pass filter with a narrow passband. Here is a picture of a Panasonic detectors sensitivity versus fc.

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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. 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.

It doesnt hurt to try if your just scavenging detectors and emitters.

Reply to
Hammy

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?

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?

Reply to
pawihte

Thanks.

Reply to
pawihte

Not sure but likely considering the availability of universal remotes.

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.

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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.

Reply to
Hammy

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.

Reply to
pawihte

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?

Reply to
pawihte

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