Low power radio transmitter

[Craig Welch]

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,

--
Craig

 

[Clifford Heath]

Craig Welch wrote:

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.

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.

 

[Jasen Betts]

On 2005-12-23, Craig Welch <craig@pacific.net.sg> wrote:

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?

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

 

[Craig Welch]

Clifford Heath wrote:

Craig Welch wrote:

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.

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.

Thanks, but the mailbox is not visible from the house. Long, curved
tree-lined driveway.

--
Craig

 

[Phil Allison]

"Craig Welch"

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?

** 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