HT12E Encoder

       HT12E is an encoder integrated circuit of 2¹² series of encoders. They are paired with 2¹² series of decoders for use in remote control system applications. It is mainly used in interfacing RF and infrared circuits. The chosen pair of encoder/decoder should have same number of addresses and data format.

       Simply put, HT12E converts the parallel inputs into serial output. It encodes the 12 bit parallel data into serial for transmission through an RF transmitter. These 12 bits are divided into 8 address bits and 4 data bits.

       HT12E has a transmission enable pin which is active low. When a trigger signal is received on TE pin, the programmed addresses/data are transmitted together with the header bits via an RF or an infrared transmission medium. HT12E begins a 4-word transmission cycle upon receipt of a transmission enable. This cycle is repeated as long as TE is kept low. As soon as TE returns to high, the encoder output completes its final cycle and then stops.

Features:

• Operating voltage: 2.4V~12V
• Low power and high noise immunity CMOS technology
• Low standby current: 0.1uA (typ.) at VDD=5V
• Minimum transmission word: Four words
• Built-in oscillator, needs only 5% resistor
• Data code has positive polarity
• Minimal external components
• Secure and robust protocol
• Ideal for remote control and security applications
• Compatible with the HT12D decoder IC
• 18-pin DIP

Applications:

• Burglar alarm system
• Smoke and fire alarm system
• Garage door controllers
• Car door controllers
• Car alarm system
• Security system
• Cordless telephones

PIN DESCRIPTION OF IC HT12E: 

The pin Description of the IC HT12E was pretty simple to understand with total of 18 pins.

• VDD and VSS: Positive and negative power supply pins.
• OSC1 and OSC2: Input and output pins of the internal oscillator present inside the IC.
• TE: This pin is used for enabling the transmission, a low signal in this pin will enable the transission of data bits.
• A0 - A7: These are the input address pins used for secured transmission of this data. These pinns can be connected to VSS or left open.
• AD0 - AD3: This pins are feeding data into the the IC. These pins may be connected to VSS or may be left open for sending LOW or HIGH bits to the encoder.
• DOUT: The output of the encoder can be obtained through  this pin and can be connected to the RF transmitter.

WORKING OF IC HT12E: 

        HT12E starts working with a low signal on the TE pin. After receiving a low signal the HT12E starts the transmission of 4 data bits as shown in the timing diagram above. And the output cycle will repeats based on the status of the TE pin in the IC. If the TE pin retains the low signal the cycle repeats as long as the low signal in the TE pin exists. The encoder IC will be in standby mode if the TE pin is disabled and thus the status of this pin was necessary for encoding process. The address of these bits can be set through A0 - A7 and the same scheme should be used in decoders to  retrieve the signal bits.

PRACTICAL CIRCUIT OF HT12E:

         The above diagram shows the practical set up of the HT12E encoder IC for better understanding on the working.

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Download HT12E :Here