I'm using these below for detecting outdoor cat. Transmitter works at 50ft, but maybe not 50M. The 9V batt lasts for nearly a year. It's thermal-IR, but if non-ambient mail is falling right across it, probably it will trigger. Or, cut into the sensor and add a leaf-switch and resistor. Perhaps extend the PCB antennas as dipoles (is it 433MHz?)
$15 wireless alarm https://www.harborfreight.com/wireless-security-alert-system-57937.html On Wed, 29 Dec 2021, Robin wrote:
I'm looking for an elegant, simple, cheap means of transmitting a single bit of information over a distance of 50 meters, without wires. Imaginative solutions sought. :) Regards, Robin van Spaandonk <mixent...@aussiebroadband.com.au>
(((((((((((((((((( ( ( ( ( (O) ) ) ) ) ))))))))))))))))))) William J. Beaty SCIENCE HOBBYIST website billb at amasci com http://amasci.com EE/programmer/sci-exhibits amateur science, hobby projects, sci fair Seattle, WA 206-762-3818 unusual phenomena, tesla coils, weird sci
