31-08-2017, 04:01 PM
Here we describe how to control electrical and electronic equipment from a remote location using radio frequency (RF) transmission. An RF interface is used instead of infrared (IR) to avoid the drawbacks of an IR interface. In addition, RF has a longer range. The signal is transmitted by an RF transmitter and received by an RF receiver to turn the desired device on or off. This system can be used to control up to fifteen devices.
Fig. 1 shows the block diagram for controlling RF-based multiple devices using a microcontroller. The keypad signals are fed to the AT89C2051 microcontroller, which, in turn, is connected to the RF transmitter via the HT12E encoder. The microcontroller continuously reads the status of the keys on the keyboard.
When any key is pressed, the data is passed to the encoder and then to the RF transmitter from where it is transmitted. The RF receiver receives this data and gives it to the RF decoder. The decoder serially converts serial bit data into four-bit data on one AT89C51 microcontroller port. The microcontroller energizes the corresponding relay via a relay controller. The devices are connected to normally open contacts (N / O) of the relays.
Fig. 1 shows the block diagram for controlling RF-based multiple devices using a microcontroller. The keypad signals are fed to the AT89C2051 microcontroller, which, in turn, is connected to the RF transmitter via the HT12E encoder. The microcontroller continuously reads the status of the keys on the keyboard.
When any key is pressed, the data is passed to the encoder and then to the RF transmitter from where it is transmitted. The RF receiver receives this data and gives it to the RF decoder. The decoder serially converts serial bit data into four-bit data on one AT89C51 microcontroller port. The microcontroller energizes the corresponding relay via a relay controller. The devices are connected to normally open contacts (N / O) of the relays.