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From: David Higton (2:221/10)
To: All
Date: Sat, 25.12.21 20:07
Re: Motion sensor that can "see" through glass
From: David Higton <>

In message <sq31e8$1dhv$>
Chris Schram <> wrote:

> On 2021-12-23, Axel Berger <Spam@Berger-Odenthal.De> wrote:
> > Chris Schram wrote:
> > > It would be used in some sort of RasPi or Arduino configuration.
> >
> > That might work, but it's a lot of hassle and complication. The doorbell
> > already is an electric signal. Could you not use that directly?
> >
> Heh! You don't know about my doorbell. It's a brass replica of an antique.
> You twist a knob on the outside of the door which spins a clapper against
> the bell on the inside. No electronics, or even electricity involved.

OK, here's a suggestion for sensing the bell (which, I recognise, isn't
what you asked for, but might be a good alternative).

Sense the movement of the clapper by optical reflection.

Either paint a white spot on it, or attach reflective tape, somewhere
that a reflective sensor can see. You may find that you need two sensors
so as to avoid the problem where the clapper comes to rest just on the
threshold of one sensor, and, despite hysteresis, you might find it's
changing state frequently and causing false triggers; if so, position a
second sensor such that it can't possibly be on the threshold at the
same time, and look for changes (in either direction) from both sensors.

I'm still looking forward to hearing what you propose as the method to
alert you, whatever the detector is.


* Origin: - the fidonet nntp junction (2:221/10)


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