I'm a newcomer to all this , so please bear with me. I am working on a project that requires a transmitter (I want to plug it in a USB port on a PC ) with the ability to send RF ( needs to go thru walls) commands over 8 different channels or frequencies to 8 receivers located up to, say 40 feet. The software program will allow the user to choose which channel or channels to transmit commands on. I am trying to avoid using a card slot or an external device. It needs to be a simple plug-in that anyone with basic computer skills can do. The receivers can be no larger than a quarter with an attached long life ( 3-4 years) battery. Each receiver will be connected to LED's and a piezoelectric speaker. The receivers do not need to communicate back to the transmitter. To top it off, everything needs to be very inexpensive. Hopefully with high volume sales, it will be affordable. Any ideas / suggestions are greatly appreciated.
Thanks in advance.
I don't even think that there are batteries smaller than a quarter that could just blink an LED once a day for 3-4 yrs let alone sit in standby listening for broadcasts and running a piezoelectric speaker + LED. What do I know, though..?
Okay peaple, now that everyone thinks I'm nuts, how about this...A receiver about 1 inch in dia. x 1/4 inch thk. PLUS a battery 1 inch dia. x 1/8 thk. , or thereabouts. Don't PC's have those little batteries that last for years running the clock etc.
Don't PC's have those little batteries that last for years running the clock etc.
Sure they do. But the power requirements of a RTC and the power requirements of an RF receiver are orders of magnitude apart.
I might as well throw this in to. The complete object , including the receiver and battery needs to retail for about $8.00. It is only receiving RF signals not transmitting, so that should not require too much power.
Window / door sensors not a bad idea. I wanted to transmit from a PC. But I will look into it. Thanks
Okay peaple, now that everyone thinks I'm nuts,
Not necessarialy nuts, but lacking significant knowledge of hardware and such to complete your project as you have stated you want it to be. I want to make a cheap/fast two person flying carpet, but for now I'll have to be content with my rio yellow 2005 Honda S2000. 
You hit the nail right on the head Richard. That's exactly what I have in mind. Yes, this is not my field of expertise, but I am getting a lot of valuable info from this post. And I am really trying to keep most of it in the U.S. It's hard to beat China's prices though.
So I can transmit 8 different messages on one RF freq.?
Got it. Thats perfect, just what I need. They are decoded at the receiver end. I will have a software program in that I chose which receiver accepts which commands.
I'll have to be content with my rio yellow 2005 Honda S2000.
You drive an S2000? Sweet!! I love those cars. I have yet to drive one, though. Sadface.
You drive an S2000? Sweet!! I love those cars. I have yet to drive one, though. Sadface.
Unfortunately they made the last ones in 2009. Don't know if they will make a replacement, so I'll have to take good care of the one I have (probably my last "big toy"). Below is the way I wish I could drive it. Bottom is a page of interesting S2000 youtube videos.
WOW! I could never be a passenger in a car with someone driving like that. ESPECIALLY without a helmet! I have a friend that owns an E46 BMW M3.. He thinks he's a racecar driver. Scares the crap out of me all the time. His car is crazy fast. Aren't we well off-topic now? haha