"MM" wrote in message
...
On Mon, 20 Apr 2015 19:48:47 +0100, GB
wrote:

On 20/04/2015 19:07, MM wrote:
In my rummage box

Have you tried a little card next to the letterbox:

"Please ring the bell after you put anything through the letter box.
Thanks."

That would be effective, and "simplest possible".

Each bell push has a laser printed label (had so
for months) saying "Please ring BOTH bells!"

Yeah, plenty don't bother to read stuff like that.

You have to realise that not everyone can read nowadays.

The posty always can because he has to read the letter/parcel label.

They can recognise house numbers and somehow
they work out which street or road they're on,

They can only do that by reading the street signs initially.

and that's about as far as their academic experience ever went.

Sure, but no one who gets to be a posty leaves
school now without being able to read.

My postie (well, one of them; I get several different ones)
can't even tell the difference between 7 and 5, because
sometimes I get the neigbour's mail and she gets mine.

I get some mail delivered to the same street number
on the next street over which has a MUCH longer
street name. I know that because the old fella who
lives there comes over and knocks on the door
and we have a bit of a chat when he does that.

The posty clearly just puts it in the wrong bin when
sorting the mail before putting it into the bag on
the motorbike.

"MM" wrote in message
...
On Mon, 20 Apr 2015 12:54:53 -0700 (PDT),
wrote:

On Monday, 20 April 2015 19:07:18 UTC+1, MM wrote:
Without the casing gubbins around it, this is quite small and compact
enough to mount on the letterbox flap. But the 64,000 dollar question
is, how long could I extend the two wires leading to the buzzer?
The buzzer looks like a small round black drum, approx 12mm dia and
about 15mm long. It has 2 wires coming out of it. It is marked P87J.
How about 3 metres? 10?

Any reasonable distance if the buzzer is the sort with internal driver
circuitry and the alarm is only sending DC volts down the wire.

Not sure if it's a bare piezo sounder relying on a driver circuit on the
main alarm board.

Will it screw the circuit board if I experiment with different lengths?

Nope, it won't do it any harm whatever you do.

Even if you put a couple of miles of bell wire on it
the worst that might happen is that it doesn't ring.

Will the buzzer just get quieter and quieter?

Not with the sort of distances that you get in a house
even if you use the very fine wire that is used in phone
extension cords and use long lengths of that.

On 20/04/2015 16:54, MM wrote:

I tried doing this, i.e. monitoring the postal deliveries, with VLC
and a web cam which streams the video capture to another networked PC,
but I have to be there to watch the remote display. VLC does have an
option to flash up changes from one frame to the next, but I haven't
found how to link those changes to an audible alert. Plus, it would
give all kinds of false triggers as other residents walk past my
house.


There's software called 'motion' on Linux that I use with a Pi and a
camera module to use as a security camera. It can be made to notify of
an event, which is a detection of motion. Could easily get motion to
toggle a gpio on the pi board to make something external happen, light,
sound, whatever. Or, indeed just use the audio out on the Pi and make it
chirp, howl, whatever.

On Monday, 20 April 2015 19:07:18 UTC+1, MM wrote:
In my rummage box I found a 20-year-old (at least) Polycell door
alarm! White in colour, this measures about 125mm x 33mm x 25mm. It
runs on a 9V battery, which, believe it or not STILL had enough power
to emit a few feeble clicks from the buzzer when I switched it on and
played around with the keeper.

Yes, there's a keeper to go on the door; the alarm is screwed to the
door frame. I never used it. It was a flash in the pan idea when I
lived near High Wycombe which had a high crime rate.

Now, I've dismantled the thing! The circuit board inside (approx 65mm
x 30mm) was fixed with two plastic "rivets" which I drilled out in
seconds.

With a new 9V battery the alarm is nice and loud as I remember it.

Without the casing gubbins around it, this is quite small and compact
enough to mount on the letterbox flap. But the 64,000 dollar question
is, how long could I extend the two wires leading to the buzzer?

long as you want

The buzzer looks like a small round black drum, approx 12mm dia and
about 15mm long. It has 2 wires coming out of it. It is marked P87J.

How about 3 metres? 10? I'd use bell cable or similar. Would extending
it by such a length eventually "blow" the components on the circuit
board (extra stress pumping the signal that much further)?

no


NT

On Monday, April 20, 2015 at 10:31:54 PM UTC+12, MM wrote:
I want to hear an alarm sound/see an LED flash when the postie posts
something through my letterbox. The letterbox has a flap on the inside
to keep draughts down. I want to attach 2 contacts to the flap and
body such that as soon as the flap opens and the contacts are broken,
said alarm/LED are triggered.

I'm worse than a novice in electronics, although I've painstakingly
soldered Velleman kits and similar before. I don't know the first
thing about circuit design, but I know enough to know what a resistor
is and what the coloured rings represent. Also, capacitors,
transistors and, above all, DIL chips such as the CMOS 4000 series.

I've reviewed several circuits on the internet, but they all seem
overkill for what I need. The problem, it seems, is getting the thing
to trigger when the circuit is OPENED.

Thanks.

MM

Having a separate street entrance I have to make a special effort to enter through another gate where the mailboxes are. I used a rubber band stretched across the top of my mailbox opening with a doubled-ended clothes peg that grabs hold of the middle of the rubber band. When mail goes in the clothes peg is pushed back and, under pressure it flips up to the roof of the letter box. I can see the front of my letterbox from the door of my apartment about 30 meters away and can tell whether the clothes peg is up or down. Unfortunately my 720p webcam doesn't have enough resolution. By attaching a tiny LED to the swinging end of the clothes peg I got its terminals to make contact with the +ve and -ve surfaces of two cr2032 batteries which I taped to a connector on the roof of the letterbox. How can I eventually make this into a Bluetooth circuit?

Well, you used to be able to get normally open or normally closed read
switches. they were often used in those little blocks mounted on opening
windows. One had the switch the other a bar magnet. When the window was
opened the magnet was taken away from the switch and it either opened of r
closed the contacts depending on the type.
All you would need was some low current circuit operating a larger relay
which had a parir of contacts used to make it latch on when it was
energised, the other pair of contacts would operat the sounder. Tto cancel
the alarm just have a push switch to break the contact in the latching
circuit when you had retrieved the mail.

I've done this with an old garage door and it worked fine till the dorr got
stuck one day...

Still the principal is the same. No need to mess e with complicated
electronics, jui ust simple dc circuit powered by a cheap DC 12 volt wall
wart.
Brian

--
From the Sofa of Brian Gaff Reply address is active
Remember, if you don't like where I post
or what I say, you don't have to
read my posts! :-)
wrote in message
...
On Monday, April 20, 2015 at 10:31:54 PM UTC+12, MM wrote:
I want to hear an alarm sound/see an LED flash when the postie posts
something through my letterbox. The letterbox has a flap on the inside
to keep draughts down. I want to attach 2 contacts to the flap and
body such that as soon as the flap opens and the contacts are broken,
said alarm/LED are triggered.

I'm worse than a novice in electronics, although I've painstakingly
soldered Velleman kits and similar before. I don't know the first
thing about circuit design, but I know enough to know what a resistor
is and what the coloured rings represent. Also, capacitors,
transistors and, above all, DIL chips such as the CMOS 4000 series.

I've reviewed several circuits on the internet, but they all seem
overkill for what I need. The problem, it seems, is getting the thing
to trigger when the circuit is OPENED.

Thanks.

MM

Having a separate street entrance I have to make a special effort to enter
through another gate where the mailboxes are. I used a rubber band stretched
across the top of my mailbox opening with a doubled-ended clothes peg that
grabs hold of the middle of the rubber band. When mail goes in the clothes
peg is pushed back and, under pressure it flips up to the roof of the letter
box. I can see the front of my letterbox from the door of my apartment about
30 meters away and can tell whether the clothes peg is up or down.
Unfortunately my 720p webcam doesn't have enough resolution. By attaching a
tiny LED to the swinging end of the clothes peg I got its terminals to make
contact with the +ve and -ve surfaces of two cr2032 batteries which I taped
to a connector on the roof of the letterbox. How can I eventually make this
into a Bluetooth circuit?

On Sunday, 29 November 2015 09:52:31 UTC, Brian-Gaff wrote:

Well, you used to be able to get normally open or normally closed read
switches. they were often used in those little blocks mounted on opening
windows. One had the switch the other a bar magnet. When the window was
opened the magnet was taken away from the switch and it either opened of r
closed the contacts depending on the type.
All you would need was some low current circuit operating a larger relay
which had a parir of contacts used to make it latch on when it was
energised, the other pair of contacts would operat the sounder. Tto cancel
the alarm just have a push switch to break the contact in the latching
circuit when you had retrieved the mail.

or just reed switch, LED & resistor.


NT