Help with building simple RF module. Please help

Hi, I am trying to build a simple RF module with a transmitter and receiver. Can someone point me in the right direction of a schematic, components list, or something along those lines? Google sprouted no answer for me. What this will be used for is a wireless relay. So when I press a button on a webpage or a physical button it sends some kind of signal to the receiver and turn's on the relay (as well as lighting up a LED). The main relay circuit uses a diode, transistor, relay, 12v battery, and when I build the receiver it will be on the board as well. Then the arduino is connected to the transmitter. Thank you :)

Do you want to build a transmitter yourself ? That is not legal. There are frequencies that are legal to use with low power. The frequencies depend on the country you live in. If you know more or less what you want, you can buy a module for transmitting and receiving. Have a look at this page, it shows what is possible with the Arduino : https://www.sparkfun.com/categories/16?sort_by=price_asc&per_page=200

These keyfob RF remotes are legal just about everywhere and too cheap to ignore. https://www.adafruit.com/products/1095 There are 3 options for the receivers, including relay outputs.

How is it not legal in U.S? All I need is a low frequency device that can at least transmit and receive inside a house, I don't really wanna buy one because it will be cheaper just to add it on my pcb in cad with the relay board. :) I guess I could compare what I need is having a wireless wire where I can send a few bytes of data over the air without using any commercial or retail rf modules :) thanks guys

Very low power transmitters that work in the standard AM and FM broadcast bands are completely legal in the U.S., as long as they meet certain restrictions. Anything that does not go much beyond your house is fine. There are thousands of web pages that will tell you how to build them.

The difficulty is building a simple receiver that will work for receiving data. Low power FM transmitters generally assume you already have some kind of FM receiver, as building an FM receiver is anything but trivial. As you can buy already built 433 Mhz Transmitters and receivers for less than $4 each , its silly to even consider building your own.

Hi, check out the electronic kit manufacturers and suppliers, you need a simple garage remote control kit. It will have everything you need.

Tom.... :)

search.jaycar.com.au/electronics/Garage-Door-Remote-Control check out the 433Mhz kit

http://www.allelectronics.com/index.php?page=seek&id%5Bm%5D=pattern&id%5Bq%5D=wireless+remote&x=26&y=8

mauried, the thing about buying them is it will be cheaper in the long run when these modules go for sale. before you ask why I am making it then and don't know how to make the RF portion. My friend owns a software that he wrote in java called jarvis. It is not commmands it actually can understand anything. free speech to the program and it can figure out what your asking and do it. He is busy with college, and I am new to electrical engineerings (I guess electronics would be correct as well). I wanted to learn more about RF so I offered to try to build it. It would be cheaper to design it on board with the relay and all the rest of the components. It is a small 1 relay board where you can plug in appliances etc and you can tell jarvis to turn them off and on and it can do it through the arduino. So it's really just going to be a relay board with on-board custom RF receiver and the arduino will have the transmitter. I couldn't find any tutorials online for how to build a simple rf trans and rec. with gnd, vcc, data line, and ANT (which I am not sure exactly what ANT is. I am assuming its not the java extension for apache web server). Also if it helps to know I have my CCNA as well so I know the basics of networking, OSI layers, diff types of mediums and all that good stuff.

ANT = antenna. You will need one for each transmitter and receiver.

The reason you wont find any tutorials on how to build simple data transmitters and receivers is simply because you cant. Data receivers that will do what you want are not simple. You need a full super heterodyne receiver which requires RF stage , Mixer , IF amplifier , Detector ,Data slicer , AGC control, Crystal Synthesised local oscillator and antenna . You also need specialised test gear including a signal generator and a frequency counter or spectrum analyser. Unless you have a very strong background in Radio Comm design then forget building the radio part of your project and buy readily available radios.

If you are in the US and want to sell something that is an intentional transmitter you will need FCC approval that will cost you several thousand dollars at least.

Thank's grumpy mike!! I will settle with buying them. :)