short range low power radio for telemetry

Apr 07, 2004 1 Replies
B

hi,



i am toying with the idea of using a small radio transmitter to transmit one (or two ideally) audio signals over a very short range (no more than a few metres) to eliminate wiring from a job i am working on. problem: the power supply for the transmitter would be limited to 3V and around 2 or 3 milliamps. is this possible? SNR would not have to be terribly high.



if so, perhaps someone can point me in the right direction here - can i expect to find a chip transceiver pair that will do this job off the shelf, or should i be thinking of building this out of discretes? or should i be looking for a complete off-the-shelf system? such things exists?



thanks in advance for any comments,



ben


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W

transmit

than

2

high.

i

exists?

Depends on how much you want to spend. You could use a cheap portable FM radio as the receiver, with the earphone output connected to a 567 PLL chip for detecting the tones, or even simpler. The transmitter could be a simple FM wireless microphone circuit minus the microphone, with two tone generators in place of the microphone. These could be a

555 to generate the tone, passed thru a low pass filter to eliminate the harmonics.

Or you could just buy a remote and receiver like those used for garage door openers. These are in the $40 range. See for example this URL

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