RE: Re: Beam Breaks - worthwhile?

["Kevin Hawkins" <lists@xxxxxxx>]

Just had a chat with Phaedrus about their motion bar - and first of all
must
say what a pleasant surprise it is to talk to a company that wants to help.
They went out of their way to see if there's an opportunity for adapting
their product to this need - and I shall let you know how this progresses
as
one is on it's way here as a free loan.  Have been very pleased too with my
VIOM module I got from them a while back too - (16 Input and 16 Output via
serial) - not as clever as IanB's soon to be released xAP enabled board
though !! ( they deserve a plug as it's so rare to feel good after a
telephone conversation with companies nowadays).

Their original 'beambar' design uses 4 beams because it was
designed to be mounted vertically (and allows for several units to be
stacked) to protect an area eg a window - thus the beams were spaced
reasonably far apart to be economic in the coverage length - whilst not
allowing people (or whatever) to squeeze between. Two beams had to be
broken
to trip an alarm , which is typical in most vertical multiple beam
arrangements - falling leaves etc.  The motion sensor came simply from
seeing a new application using the existing hardware. So this means there
was no essential technical reason why the beams couldn't be closer - or
indeed that four were needed - I shall have a try at narrowing the gap and
see what the effect is. It may well be achievable in a two beam design as
well.

A couple of interesting points were made. The sensors could be
mounted diagonally and still sense direction - this reduces the width
requirement to 15cm. However you need to ensure that beams are broken in
order - if for example a middle beam is broken first it gets confused - if
you mount diagonally there is an increased risk of this happening - eg hand
ahead of body - or carrying something.

I'll report back in due course..



Paul - re your comment below there are some quite fancy beams
that work on reflected light, both indoor and outdoor - for example the
RetroVisor form http://www.rv-ltd.demon.co.uk
<http://www.rv-ltd.demon.co.uk/>
 - when they get clever and long distance
(as this one is 30M ) they get expensive too though.



K







-----Original Message-----
From: Jon Payne [mailto:jgpayne@xxxxxxx]
Sent: 14 August 2003 16:26
To: ukha_d@xxxxxxx
Subject: Re: [ukha_d] Re: Beam Breaks - worthwhile?



I was thinking also that two may be needed for direction i.e. when you
enter
the lounge the light comes on, but not when you leave it...

jon
----- Original Message -----
From: "Paul Robinson" <ukcueman@xxxxxxx>
To: <ukha_d@xxxxxxx>
Sent: Thursday, August 14, 2003 3:56 PM
Subject: Re: [ukha_d] Re: Beam Breaks - worthwhile?


> Is a receive/transmit pair the only reliable way to do this?
>
> ISTR something that was both transmit and receive, relying on a
reflection
> to operate. Is there such a beast or did I imagine it?
>
> ----- Original Message -----
> From: <ian.bird@xxxxxxx>
> To: <ukha_d@xxxxxxx>
> Sent: Thursday, August 14, 2003 3:35 PM
> Subject: Re: [ukha_d] Re: Beam Breaks - worthwhile?
>
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