RE: Electronics help & Light beam sensors

["Ian B" <Ian@xxxxxxx>]

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@xxxxxxx]
>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
>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.
>
>
>
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