Re: Electronics help & Light beam sensors

["psghome2002" <psghome@xxxxxxx>]

Thanks Ian,

I'd be interested to see the article although I have now just seen a
dual beam break sensor for =A335 on the Maplin web site. I guess it
might be quicker and easier to try this? It quotes a 30m range with
relay contact output. It does say indoor use but I guess it should
be OK in the garage.

On another related query - I've been thinking about how to sense
when the garage door is open or closed. I could use a set of micro
switches and relevant levers etc but then thought why not use the
travel limiting switches in the electric door opener? The main
gearing cogs have an open and closed limiter which is adjustable and
makes contact with two micro switches. These switches are obviously
then used to stop the motor when reached.

I'm not sure if I can 'tap' into this switch in parallel and use it
as an input to HomeVision without affecting the door opener
circuitry? Would I need to isolate it in some way?

Cheers,

Paul.

--- In ukha_d@y..., "Ian B" <Ian@M...> wrote:
> Hi Paul
>
> I read something recently about beam breaks and the strategy was
in that
> case to modulate the IR to 36 Khz but then speed things up again
by a factor
> I don't remember. (Read the article) OK, the on period is again
modulated
> onto 300 Khz. The net effect of this meant that the system was
very low
> power consumption and immune to most IR sources e.g. remotes.
Direct
> sunlight might need some shading but that would not be a problem
for you.
>
> There was no range quoted but it uses a TSOP or similar and 555
timers. If
> you like I can dig out the article and mail it to you or if more
folks want
> to read about it I will put it up on my site - you guys choose.
>
> Ian B
>
> >-----Original Message-----
> >From: psghome2002 [mailto:psghome@h...]
> >Sent: 23 June 2002 14:58
> >To: ukha_d@xxxxxxx > >Subject: [ukha_d] Electronics help & Light beam sensors
> >
> >
> >I'm trying to make up a combined parking sensor and garage door > >safety switch to be fitted to the inside of the door frame and
> >looking across the opening (double garage width). I imagine the > >output to be linked to HomeVision which, in turn, will allow my > >Comfort system to close the door (or not) depending on any number =
of
> >factors I choose to program. I'll also have a couple of high
> >intensity LEDs (red and green) mounted in a box on the far end of<= BR> > >the garage wall so I can tell when the cars are far enough in to > >close the door (or if there's an obstruction).
> >
> >The signalling, interface to the electric garge door and LED's are=
> >pretty simple and not a problem but the light beam sensor is. I > >bought one of those Velleman kit form beam break sensors that uses=
> >two IR LED's (transmit) and a single receive LED. Unfortunately the
> >range is about half of what I need. I'm also wondering if IR beam =
is
> >the best technology to use (poss interference from remotes,
sunlight
> >etc)?
> >
> >The transmit circuit looks pretty simple with just a few
resistors,
> >capacitors and three transistors. Might it be possible to boost the
> >transmit power enough using this circuit, or should I look for
> >another sensor - I've had a look at what RS offer but most of them=
> >are pretty expensive and only a few offer the range I need.
> >
> >Any thoughts / suggestions?
> >
> >Thanks,
> >
> >Paul.
> >
> >
> >
> >For more information: h= ttp://www.automatedhome.co.uk
> >Post message: ukha_d@xxxxxxx > >Subscribe:  ukha_d-subscribe@xxxxxxx > >Unsubscribe:  ukha_d-unsubscribe@xxxxxxx > >List owner:  ukha_d-owner@xxxxxxx > >
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> >
> >

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