Not the remote-control receiver
The TK64 Infrared Receiver and the TK15 IR Receiver have nearly the same name and do opposite jobs. The TK64 measures how much infrared light arrives, steady or flashing, as a voltage on SIGNAL. The TK15 decodes a remote control's 38 kHz bursts and ignores steady light. Pick by the job: a beam or a reflection, TK64; a remote, TK15.
Two blocks, one word apart
The silkscreen on this block says INFRARED RECEIVER. The TK15 IR Receiver says nearly the same. They are not two versions of one thing.
The TK15 is built around a Vishay TSOP18138: a light sensor, an amplifier, a 38 kHz filter and a decoder in one small package. It answers only to light that flashes 38,000 times a second, the way a remote control sends, and it pulls its SIGNAL LOW for each burst. Anything steady it ignores on purpose.
The TK64 is a bare light sensor, an Everlight PT334-6B phototransistor, and a resistor. It has no filter and no decoder. SIGNAL is a voltage that follows how much infrared arrives: near 0 V in the dark, higher in more. That is what ACTIVE HIGH on its front means.
The same light, two answers
Press Remote button. The TK15 turns each burst into a clean LOW, which the IRremote library turns into a button code. The TK64 rises with each burst too, but slowly, and it cannot tell one button from another.
Now press Steady beam. The TK15 stays HIGH, as if nothing had happened. The TK64 rises and stays up for as long as the beam lasts. That is why the TK64 is the half of a break-beam pair with the TK63 Infrared Transmitter, and the TK15 is not.
Press Sunlight. The TK15 ignores it. The TK64 does not: sunlight carries a lot of infrared, and the reading goes to the top. Much of this book is about living with that.
Which one you want
- A beam across a doorway, an object near the sensor, how much infrared a lamp gives off: the TK64.
- A TV remote, or one board sending codes to another: the TK15, with the TK16 IR Sender on the other side.
When it does not work
No. A remote sends its code as bursts of a 38 kHz carrier, and a button is only a pattern of those bursts. The TK64 has no filter or decoder for them: its reading rises and falls as the remote flashes, but it cannot tell one button from another. The TK15 can, with the IRremote library.
Not a steady one. The TK15's chip is built to ignore light that does not flash at 38 kHz, which is how it shrugs off sunlight and lamps. A steady beam looks to it like one more lamp. For a break-beam, use the TK64.
Look at the part on top. The TK64 has a black 5 mm dome standing up off the board, and its back says TK64 INFRARED RECEIVER and DETECTS INFRARED LIGHT. The TK15 has a small receiver lying flat in a metal shield.
It was wrong on both counts. The part is an Everlight PT334-6B phototransistor, and the board has no decoder: SIGNAL is an analog voltage, near 0 V in the dark and higher in more infrared.
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