RF based REMOTE CONTROL

Introduction:-
                  The rf transmitter a gadget that disseminates radio waves with the help of an antenna. A rf transmitter consists of an oscillator that changes electrical power in to a reasonable frequency. There is also an amplifier for audio frequency (AF) and radio frequency (RF). A modulator regulates the signal information on to the transmitter for dispersion. The rf transmitter has an important component that makes its working possible; this is the antenna that transmits an electromagnetic signal for many types of communication. rf transmitter works together with rf receivers. There must be rf receivers on the other end for transmitters to play their role. Communication by use of these systems is possible for radios, cell phones, televisions, walkie –talkies and other electronics used for the purpose of broadcasting. It is possible to find both rf receivers and transmitters in one device. A good example of such technology is used in mobile phones where one can receive and call using one gadget. Currently communication does not rely on analogue mode but uses digital technology thus eliminating the need for complex wiring system to do the connections that carry information.

For an example: We will be using ASK (Amplitude Shift Keying) based Tx/Rx(transmitter/receiver) pair operating at 433 MHz. The transmitter module accepts serial data at a maximum of XX baud rate. It can be directly interfaced with a microcontroller or can be used in remote control applications with the help of encoder/decoder ICs.

RF transmitter module:-

RF transmitter module

RF receiver module:-

RF Receiver module

Working:-

The encoder IC takes in parallel data which is to be transmitted, packages it into serial format and then transmits it with the help of the RF transmitter module. At the receiver end the decoder IC receives the signal via the RF receiver module, decodes the serial data and reproduces the original data in the parallel format.In order to control say a dc motor, we require 2 bits of information (switching it on/off) while we need 4 bits of information to control 2 motors. HT12E and HT12D are 4 channel encoder/decoder ICs directly compatible with the specified RF module.In order to drive motors, we would need to connect a suitable motor driver at the output of the decoder IC. The motor driver circuit can consist of a relay, transistorized H-Bridge or motor driver ICs like the L293D, L298 etc. 

Block Diagram:-

Application:-


                 Rf transmitter enables you to make use of your television, radio, phone and other communication hand held devices. Rf receivers are installed in these devices in factory to make them respond to any signal send. A rf transmitter may interfere with other communication services. This means that you should take precaution by seeking from the relevant authorities about the mode of frequency to use when installing your communication system. Rf receivers are capable of receiving broadcast information from a rf transmitter in different patterns like a single beam or broadcast system. You cannot however tell the difference when you are listening from your radio or watching TV. Rf receivers function hand by hand with transmitters so none can be on its own. Communication is hence a two-way traffic and some communication models are accommodating the receiving and transmitting factors in one equipment. These functions perform well by the energy from electricity or solar. The major important thing in a communication system is to send and receive feedback. Modern times have included the aspect of time in the instruments of passing information no matter how far you are located. This would however be impossible if it was not for transmitters and receivers.

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What is RFID

 
RFID stands for Radio-Frequency IDentification. The acronym refers to small electronic devices that consist of a small chip and an antenna. The chip typically is capable of carrying 2,000 bytes of data or less.
The RFID device serves the same purpose as a bar code or a magnetic strip on the back of a credit card or ATM card; it provides a unique identifier for that object. And, just as a bar code or magnetic strip must be scanned to get the information, the RFID device must be scanned to retrieve the identifying information. 

Working

A Radio-Frequency IDentification system has three parts:

• A scanning antenna
• A transceiver with a decoder to interpret the data
• A transponder - the RFID tag - that has been programmed with information.

The scanning antenna puts out radio-frequency signals in a relatively short range. The RF radiation does two things:

• It provides a means of communicating with the transponder (the RFID tag) AND
• It provides the RFID tag with the energy to communicate (in the case of passive RFID tags).

This is an absolutely key part of the technology; RFID tags do not need to contain batteries, and can therefore remain usable for very long periods of time (maybe decades). The scanning antennas can be permanently affixed to a surface; handheld antennas are also available. They can take whatever shape you need; for example, you could build them into a door frame to accept data from persons or objects passing through.
When an RFID tag passes through the field of the scanning antenna, it detects the activation signal from the antenna. That "wakes up" the RFID chip, and it transmits the information on its microchip to be picked up by the scanning antenna.

In addition, the RFID tag may be of one of two types. Active RFID tags have their own power source; the advantage of these tags is that the reader can be much farther away and still get the signal. Even though some of these devices are built to have up to a 10 year life span, they have limited life spans. Passive RFID tags, however, do not require batteries, and can be much smaller and have a virtually unlimited life span.
RFID tags can be read in a wide variety of circumstances, where barcodes or other optically read technologies are useless.

• The tag need not be on the surface of the object (and is therefore not subject to wear)
• The read time is typically less than 100 milliseconds
• Large numbers of tags can be read at once rather than item by item. 

Passive RFID vs. Active RFID

Passive RFID tags operate using power from the RFID transceiver. Passive tags are small and inexpensive, but do not have good range.
Active RFID tags are powered, usually by a battery. Active tags are larger and more expensive, but offer a much better identification range.
RFID tags store data, which is typically used for authentication. Passive tags typically store between 32 and 128 bits of data; Active tags can store up to 1MB of data.
Passive tags are Read-Only; Active tags are typically rewritable.

Applications

Please click at one of the applications below to read how Rotil Communications B.V. applied these techniques successfully at previous projects.

• Vehicle start interruption
• Access control and identification
• Petrol stations
• Working hours registration system

Other possibilities to apply the RFID technique are for example:

Vehicle identification

Every vehicle will carry a transponder. Through the unique id number in the transponder it will be easy to ‘recognise’ the vehicle. This can expanded with the registration of technical vehicle information such as temperature, GPS location.

Logistic processes

Every container, box or crate has a transponder fitted to it. With each step in the process, the transponder is being read and the operation is saved in the central database. By this is, it will be very easy to find out which steps in the production process has already been made.

Service and maintenance

All products, devices or vehicles will get a transponder. The service or maintenance mechanic scans this transponder for each maintenance. The software on a computer, which is connected to a central database, enables him to register for example the product details, customer number, maintenance tasks, date/time. Now it will be much easier to find out which maintenance or service has been provided to a certain product/vehicle with just a click. This will be very (cost) efficient.

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