IR Transmitter with HT12E

IR (infra-red) transmitters containing the encoder-IC HT12E from Holtek have been published in Elektor Electronics on previous occasions. The interesting aspect of this design is that the entire IR-transmitter has been squeezed into a handy key ring.The operation of the encoder IC HT12E has already been thoroughly dealt with in earlier publications. It will suffice to mention here that an address can be programmed on inputs A1 through to A8. This address has to be set the same as in the receiver.

Resistors:
R1 = 976kOhm 
R2,R4 = 10kOhm 
R3 = 100kOhm 
R5 = 10Ohm 
Capacitors:
C1 = 100nF
C2 = 100µ F 10V radial
C3 = 10nF
C4 = 220pF
Semiconductors:
D1 = 1N4148
D2 = IRED (e.g., LD274)
IC1 = HT12E (Holtek)
IC2 = TLC555
T1 = BC337
Miscellaneous:
S1 = miniature pushbutton (HAK)
Enclosure: KM series Box UM14
PCB, available from The PCBShop