Re: Door Bells.

[kimble <kim4@xxxxxxxxxxxxxxxxxx>]

Ali Watkins wrote:

<unlurk>
> Just wondering if anyone has (or has seen) a wireless doorbell that
has
> some kind of external latch that pulses when its rung, instead of just
> the speaker.  Ideally this would be a small LED or a light or
something!
>
> Does anyone else have their doorbell wired into the pc?

Have done exactly this - cheap[1] wireless[2] doorbell (tenner from
B&Q)
into PC's parallel port[3].

The receiver turned out to be a cheap all-in-one-chip job, so no chance
of finding a nice logic signal to go on.  What I did was take the audio
signal, rectify it with a diode, smooth it with a capacitor, and use
that signal to trigger a small transistor which pulls the parallel port
pin low (I'll attempt ASCII-art):


+--------O
+5V
10k


+--------O
Audio                / c    DATA
O--->----+----+-----
D1            b\  T1
---          e
C1 ---
R1
Audio                      GND
O---------+----+-------+--------O


You'll have to play around with the values of C1 and R1 - I've no idea
what I used, and you might need different values depending on how long
you need the signal to be present and the tune the doorbell plays.

Note that this ties one of the audio lines to the signal ground on the
parallel port, which may cause Issues if you decide to power the
receiver from something which also connects to this ground (original
batteries or a 'floating' wall-wart should be okay).

</unlurk>


kim.
xxx

--
[1] Painfully cheap.  The thing only seems to be reliable within about
5-6 metres of the receiver, although some of that could be down to the
walls, which are impervious to wireless LAN signals too.  It does
however do a fantastic job of picking up mobile phone signals if you're
silly enough to leave your phone lying too close to the receiver.
Knock-Down-Ginger over SMS.

[2] Wireless as this is a rented house, and we fear for our deposit if I
were to start drilling holes in things.

[3] Which then goes on to make a fuss on IRC and trigger strobe
lights[4] around the house in a specific pattern, for those of you
wanting a silent wired wireless doorbell  :)

[4] My partner is Deaf.