Ratio transmission project

Thread Starter

stoopkid

Joined Mar 3, 2011
146
I want to make a very basic radio project that involves two units. One unit has a motion detector that output a high or low and the other that reports that high or low and if possible, can also confirm that it is receiving a signal. I would be fine with it "expecting" a low response and alerting me for either a high or a loss of signal but I would prefer being able to differentiate between the two. I have experience with the arduino but if possible I'd like to avoid it to save power and be able to use batteries.

I'd appreciate any insight but where I'd like to get started it the radio connection. Whenever I google for it I just get info on am/fm broadcast but I'm just interested in simple communication. Just a high/low but maybe on 2-3 frequencies(although just one would really do it). I'm looking for the most economical way of communication at a distance of maybe around 15 meters(however I can be flexible).

Thanks.
 

R!f@@

Joined Apr 2, 2009
9,682
Try Ebay to find a suitable transmitter.

If u are on a learning curve, try googling for info on AM and FM Modulation and it' basic circuits
 

ErnieM

Joined Apr 24, 2011
8,011
SparkFun has some legal transmitters and receivers, fairly inexpensive too as I recall.

Sorry their sight does not search well for me or I would provide specific links.
 

Wendy

Joined Mar 24, 2008
21,929
That or design something that can be activated via tones through two wires and a capacitor. That can be sent via simple radio. FM transmitters are a dime a dozen, while receivers can be bought of the shelf.
 

Thread Starter

stoopkid

Joined Mar 3, 2011
146
I found the sparkfun ones. Although they mention that they require filtering of the signal because of interference so while it would work, it seems like I would need a micro controller on both ends. I was hoping for something that simply sends/receives a high/low signal for simple application. Is that doable or should I just forget about it being that simple? Could that be done with an FM transmitter?
 

Thread Starter

stoopkid

Joined Mar 3, 2011
146
Ok, so I have this remote control outlet switcher. When you press the button on the remote, whatever is plugged into the receiver turns on or off. You don't even get to pick, it's just a toggle. How does this work? Do I need to send a code or can it be simpler? That's how simple I need it. I just want to move that High/Low signal over radio.
 

Wendy

Joined Mar 24, 2008
21,929
Ever hear of FSK (frequency shift keying)? This can be detected with a PPL (phase locked loop) or a simple amplitude detector using a low pass filter or a high pass filter.

It could also be tested with the scheme I mentioned in my earlier post.

It isn't the only way, but it would work. A simple 555 (or similar) circuit could be used to modulate a 1 or a 0 (not to be confused with the FM radio signal). The frequency representing the 1/0 would be feed into the FM transmitter.

The reciever would have a frequency discriminator (big words, simple circuit) that would translate the base oscillation back into a 1/0.
 
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