If this is the wrong group for this question, I'm sure you will all tell me to sod off, so ...
My mail box is a few hundred yards from the house. I'd like to put a micro switch in the box, and switch on a low power (milliwatts) transmitter to activate a receiver and LED in the house.
Anyone have any good ideas? Can email me a circuit or point me to one on the web?
Thanks,
By far the easiest way is to use an optical transmitter (narrow angle super-bright LED) and use your eye as a receiver. Add a flasher circuit that powers it for a tenth of a second every two seconds, and the batteries will last years.
Talking Electronics did a low powered FM-band tone transmitter based around a common 4000 series CMOS chip they called it "water bug" in their "More FM Wireless Bugs" publication IIRC.
For a receiver you could modify a surplus receiver by adding some sort of VOX circuit (IIRC T.E. did one of those too).
talkingelectronics.com.au
actually they have a whole bunch of different transmitters for less than $15 per kit.
Bye. Jasen
Thanks, but the mailbox is not visible from the house. Long, curved tree-lined driveway.
"Craig Welch"
** Idea:Buy two cheap UHF CB radios - circa $65 a pair.
Use the micro-switch on the letter flap to trigger a timer to power up the CB in the mail box for a few seconds so it can send a call tone to the one in the house. This will save massively on battery life.
The one in the house is powered from an adaptor an left on 24/7.
Additional idea:
Have the timer re-send a call tone each 15 minutes until manually re-set by someone at the box.
......... Phil
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