pulse tx and reception

[mihir08]

hey guys i wanted to know how can i Radiate a square wave generated from a micro controler ( 100 khz suppose ) and receive it at some distance and give to to another micro controler .

all i want is " IF an event occurs at 1st micro controler " it should be indicate to other micro contoller using radio waves !

 

[betwixt]

That's a very dangerous strategy.

Basically, all you are asking to do is modulate a radio carrier and detect it's presence remotely which is easy to do. However, there are many sources of radio signals and most of the 'bad' ones you need to ignore are repetitive ones. The worst sources are switch mode power supplies, TV scanning circuits and fluorescent lights, particularly low energy ones. Any of these could produce a signal almost indistinguishable from your transmission source.

You need something in your transmission that makes it easy for the receiver to verify where it came from. For example, if the ASCII bits for the name "mihir08" were sent serially instead of just a square wave, the chances of it being accidentally picked up are trillions to one.

Consider using a UART at your transmitting micro controller and another UART at the receiving micro controller, this would allow you to send real data across the link, either just for identification or to carry other information as well.

Also bear in mind that a 100KHz square wave modulating a radio carrier will take up a huge chunk of band space!

Brian.

 

[mihir08]

thanks a lot Brian . opend my eyes ! can u give any link to the circuit which will do the work . or some keyword to google for ?

thanks
mihir

 

[eetom]

(1) A square wave is made up of many harmonics. So if the reciever has a tuned input to any of those harmonics (lower ones) then it will detect the RF signal.

(2) Input your square wave into a bandpass filter preferrably tuned to the fundametal frequency of the square wave. It will output a sinusoidal then. Your reciever input tuned circuit will only respond to a sinusoidal.

Add these ideas to the previous poster about noise and detection.