David Deley wrote:
Good idea protecting the computer input. I hadn't thought that far yet.

I'm using "The MailMinder Wireless Mail Alert" device I purchased for
only $12. A little transmitter box attaches to the mailbox door inside,
detects when the door is tilted open and sends a signal. I was surprised
the receiver actually worked in the house--I thought that would be too
far away with too many walls blocking the signal.

However, problems with the inexpensive receiver a

. There's no way to turn the receiver off
. There's no way to stop it from sounding an alert when you open the
mailbox to insert outgoing mail, or to retrieve your mail.

But for $12 it's a nice start.

Thank you for all the suggestions.

http://members.cox.net/deleyd/


OK, I see there is some kind of receiver here, with a LED on it.
Now, all you need, is a way to connect that to the computer.

http://ecx.images-amazon.com/images/...4L._AA280_.jpg

The easiest thing to do, would be to use your computer as a
source of power for the receiver. The Molex disk drive connector
has +5V and +12V on it. If you need some other voltage, you can use
a three terminal regulator. For example, this one might make 3.3V
from a 5V input for you.

http://search.digikey.com/scripts/Dk...1086CSX-3.3-ND

If the receiver used a 9V battery, you could use the 12V on the
Molex, plus a three terminal (linear) regulator, to create 9V.

http://search.digikey.com/scripts/Dk...LM2940T-9.0-ND

There are various ways to get the signal from the LED on the receiver,
into your computer. A photodarlington would be a relatively simple solution,
but you'd need a light tight box around the photodarlington and the receiver
LED, so only the LED could trigger it. This converts light, into an
electrical signal. The Darlington pair is two transistors cascaded, so
that the gain is higher. There might be sufficient gain, to drive
a logic signal (like on a game paddle switch) directly. Darlingtons are
not fast, but would be suited to the low speed detection, of a light or
LED going on. The ones I have in my junk bin, don't have part numbers,
and I fiddle with them until they work :-)

http://search.digikey.com/scripts/Dk...&name=BPW38-ND

You could also connect directly to the receiver circuit (open up the
receiver, and add circuitry to it), but that is getting pretty complicated.
If there is sufficient swing on the signal driving the LED, you might
buffer a logic signal from that with a single transistor. Radio Shack
still carries stuff like that.

http://www.radioshack.com/product/in...ductId=2062586

But at least your $12 purchase, has solved most of the important
problems for you. No lightning to worry about.

Paul