I don't use the word "modulated" very much and I would like to make sure I use it correctly. The TSSP77038 IR receiver module is a device that detects infrared light turning on and off quickly at a frequency of 38 kHz. When it detects light like that, the output goes low and stays low until the signal disappears.
Is it appropriate to describe the TSSP77038 as a "38 kHz modulated IR sensor", since the infrared light wave needs to be turned on and off at 38 kHz? Or would the word "modulated" only apply to the gaps that one would insert into a 38 kHz IR signal in order to transmit actual data?
Opinions are welcome, but the best answers will cite trusted sources or make a compelling argument.
Additional info
The TSSP77038 datasheet does not use the word modulated.
Wikipedia describes modulation this way:
In electronics and telecommunications, modulation is the process of varying one or more properties of a periodic waveform, called the carrier signal, with a modulating signal that typically contains information to be transmitted.
Best Answer
In this context, the 38 KHz signal is considered to be the carrier signal. The detector will change state whenever it sees the appropriate light frequency that is chopped at that frequency.
The modulation that they are speaking of is turning that 38 KHz carrier off and on. This modulation is what carries the information being transmitted to the receiver.
So you have 3 things in play here:
1) the photo detector inside the receiver module wants to see a specific wavelength of light (normally IR)
2) the electronics inside the receiver want to see that light turning off and on at a specific frequency (38 KHz carrier)
3) the data that you want to transmit turns the carrier off and on according to the data actually being sent. This modulation causes the output pin of the receiver module to represent that data.