This circuit confuses the infra-red receiver in a TV. It produces a
constant signal that interferes with the signal from a remote control
and prevents the TV detecting a channel-change or any other command.
This allows you to watch your own program without anyone changing the
channel !! The circuit is adjusted to produce a 38kHz signal. The IR
diode is called an Infra-red transmitting Diode or IR emitter diode to
distinguish it from a receiving diode, called an IR receiver or IR
receiving diode. (A Photo diode is a receiving diode).
There are so many IR emitters that we cannot put a generic number on
the circuit to represent the type of diode. Some types include: CY85G,
LD271, CQY37N (45¢), INF3850, INF3880, INF3940 (30¢). The current
through the IR LED is limited to 100mA by the inclusion of the two
1N4148 diodes, as these form a constant-current arrangement when
combined with the transistor and 5R6 resistor.
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