On-Off Keying Modulation for remote control

[amirahmadian]

Hi.
I've been trying to build a simple radio remote control system. I wish to use microcontrollers (AVR micros) as the heart of transmitter and reciever circuits. The system is going to be simple, it transfers just two different commands (I represent them using binary codes). Also the distance of transmission won't be very high (about 20-30 meters).
I've learned about On-Off Keying Modulation method (OOK) recently and I hope I can use it in designing my remote control system.
I think building the transmitter is not so difficult, because the micro just has to switch the carrier wave on and off (according to the bit that is being sent). Also I'll need a kind of oscillator circuit to make the carrier wave.
But the main problem is in the reciever. What kind of circuit should I use to detect the carrier wave? How can the presence of carrier be determined and be converted to a logical value readable by the micro? (I prefer easy methods!) After the micro recognizes presence of the wave, I think it will be easy to decode the bits and detect the command (However I'll need a protocol to distinguish one and zero bits, but it's not a trouble).
Another question is about noise. When the carrier wave is not transmitted, doesn't noise affect the reciever? (Reciever may mistake noise for carrier?)
And the last question, What frequency is suitable for the carrier?

Thanks :smile:

 

[FvM]

To avoid re-inventig the wheel (or at worst case the square wheel), why don' you use available cheap ASK (OOK) RF modules? 433 MHz can be used license free in many countries.

If the solution is too simple, you can still build your own transmitter and receiver with available RF ICs. At least you'll learn much about suitable RF transmission techniques by reading the available manufacturer documents.

 

[amirahmadian]

why don' you use available cheap ASK (OOK) RF modules

Actually I don't like to use modules. In fact, I can not! Sorry I can't tell you the exact reason but this project has to be a little more flexible and using modules may make some problems.

you can still build your own transmitter and receiver with available RF ICs

Could explain more about these ICs, please? Could name some of them?

 

[FvM]

Manufacturers for sub-GHz small radio devices are e.g. TI, Analog Devices, Hope RF, Microchip, Silicon Labs.