HT12D (RF Decoder IC)

The IC HT12D can be used only with its pair HT12E. These two ICs together form an Encoder and Decoder pair. They are 12-bit Encoders/Decoders, meaning they can transmit 12-bit a data among them. But your encoder IC should not communicate with someone else's decoder IC, so an Encoder and Decoder IC pair will share a common Address which is an 8-bit data. So out of the 12-bits 8-bits will be used to set address and the remaining 4-bit will be used to transmit data.  With 4-bit data we can create 16 types (2^4 =16) of combinations. These IC’s are commonly used with RF pairs or IR pairs. So if you are working on a project which has to transmit a 4-bit data from one end to other either by wire or wireless then this IC pair will be best suited for you.

The primary function of HT12D is to decode the 12-bit that is received by the input pin. Since the IC comes with an in-built Oscillator it is very easy to make this IC work. The IC is should be powered by 5V (pin 18) and the ground pin (pin 9) is grounded. For decoding a data the IC will requires an oscillator, luckily this IC has one in-built. We just have to connect the OSC1 and OSC2 (pin 15 & 16) through a 470K resistor to invoke it. The 4-bit data that is received can be obtained on pins AD0 to AD1 and an address of 8-bit has to be set using the pins A0 to A7. It is very important that your Decoder should have the same address of that of the encoder. A basic circuit diagram for the HT12D IC is shown below

In the above circuit I have set the 8-bit address data as 0b00000000, by connecting all address pins to ground. If you want security you can connect any of the 8 pins to 5V to make it high. The complete IC is powered by a +5V supply which could be obtained from a voltage regulator like 7805.The pins AD3, AD2, AD1 and AD0 are connected to any Digital IC that can read the 4-bit data. They can also be connected to LED to physically view the received data. In this the 4-bit output data is just shown as “?” since we do not know what the Encoder IC has sent to the Input pin. If any valid data is received they can be obtained from these four pins.