Review on Gikfun Digital 38kHz IR Receiver Transmitter Sensor Module Kit for Arduino (Pack of 3 Sets) EK8477 by Chris Ostby

for 38KHz IR remote controls. The emitters are standard IR emitting LEDs - there is no internal/external oscillator on the emitters. Another cool thing about transmitters is that they have 3 pins: VCC, GND, SIG, but actually only 2 pins are needed. The transmitter has a red LED for visual display. The receivers are also 3-pin: VCC, GND, SIG - the SIG output is active low. A red LED is also available here for visual display. They're primarily used for IR remote control, but I've used them to develop an Arduino morse code transceiver (instead of radio hardware). Morse code "pulses" are much wider than normal IR clock pulses. The IR receiving device contains an integrated circuit that filters and decodes the clock envelope. It also includes automatic gain control (AGC) circuitry that "saturates" when the clock envelope is too long. The workaround is to use one of the Arduino timers to generate a 38kHz square wave, 50% duty cycle and an open on a digital pin. . The interrupt service routine counts the number of interrupts and "closes" the square wave for 8 clocks and turns it off for 8 clocks and outputs it to another digital pin. This pin supplies the (-) side of the IR emitter. The morse code digital output pin powers the (+) side of the IR emitter.