Synopsis

The encoder then converts this 4 bit parallel data into serial data, i.e. generates a code for each parallel data input.  The output from the encoder is connected to the reset pin of the time 555 such that the timer will operate only when there is any output from the encoder.  The timer produces a 38KHZ signal used to drive the IR LEDs, thus producing a modulated 38 KHz IR signal.

 

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Parts List

  • R1 – 100Ohms
  • R2 – 50K
  • R3 – 10K
  • C1 – 10uF
  • C3, C2 – 10uF
  • V1 – 5V
  • U1 – HT12D
  • U2 – AT89C51
  • U3 – ULN2004
  • Q1 – BC547
  • J1, J2, J3, J4, J5