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FWIW, I've found that Genie-brand garage door "photo-eye" pairs are
easy to use in other applications. One of the two devices is a
modulated IR source with a collimating lens; the other is a sensitive
IR receiver. They are enclosed as "semi-weather-resistant" and
commonly available as replacement parts for as little as $15/pair.

The two devices must be connected in parallel (via screw terminals;
polarity does not matter) and both powered by 12vDC through a
100-ohm resistor. When the two sides can see each other (an unbroken
beam), continuous ~300uS, ~6-volt pulses appear at ~300Hz across the
resistor. Expressed differently, a ~6v ~300Hz signal rides on 12vDC
power when the beam is unbroken.

The receiver also works to receive conventional IR-remote signals,
like from a TV remote, and can be remoted simply at the end of any
pair of wires. It is quite sensitive, it appears. The IR modulation
is seen as a ~6v signal on power.

http://www.prodoorparts.com/products/112.cfm , for example, but they
are often on ebay.
Tom



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That is cheap Tom. What sort of range have you found with them? To date
I've probably used several hundred Omron equivalents on automatic gates,
and they cost about USD300 per pair! They are a little more user
friendly with relay out, but nevertheless, still expensive.

Tom Becker wrote:

> FWIW, I've found that Genie-brand garage door "photo-eye" pairs are
> easy to use in other applications. One of the two devices is a
> modulated IR source with a collimating lens; the other is a sensitive
> IR receiver. They are enclosed as "semi-weather-resistant" and
> commonly available as replacement parts for as little as $15/pair.
>
> The two devices must be connected in parallel (via screw terminals;
> polarity does not matter) and both powered by 12vDC through a
> 100-ohm resistor. When the two sides can see each other (an unbroken
> beam), continuous ~300uS, ~6-volt pulses appear at ~300Hz across the
> resistor. Expressed differently, a ~6v ~300Hz signal rides on 12vDC
> power when the beam is unbroken.
>
> The receiver also works to receive conventional IR-remote signals,
> like from a TV remote, and can be remoted simply at the end of any
> pair of wires. It is quite sensitive, it appears. The IR modulation
> is seen as a ~6v signal on power.
>
> http://www.prodoorparts.com/products/112.cfm
> , for example, but they
> are often on ebay.
>
> Tom
>
>------------------------------------------------------------------------
>
>No virus found in this incoming message.
>Checked by AVG Free Edition.
>Version: 7.5.516 / Virus Database: 269.19.0/1216 - Release Date: 9/01/2008 10:16 a.m.
>
>



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> ... They are a little more user friendly with relay out...

I guess that's part of what the $300 buys, and they are probably
industrial-grade bullet-proof enclosures. These sure aren't that - but
I guess they handle the garage environment sufficiently, and I've got a
few doing real work. I used two pairs of these sensors to surround
swinging restaurant kitchen service doors - to mute the kitchen staff's
music when the doors were open to the dining room; I needed a relay
closure for that task so the glue was more involved - but to feed a
processor, converting the 6v 300Hz signal to a logic level is just a
single NPN stage.

Mounted high on the door frames, away from a mop or a cart, they have
done fine.
Tom



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At that price, I can see a myriad of uses. Hopefully there is a NZ
agent, else the price will escalate.

Tom Becker wrote:

> > ... They are a little more user friendly with relay out...
>
> I guess that's part of what the $300 buys, and they are probably
> industrial-grade bullet-proof enclosures. These sure aren't that - but
> I guess they handle the garage environment sufficiently, and I've got a
> few doing real work. I used two pairs of these sensors to surround
> swinging restaurant kitchen service doors - to mute the kitchen staff's
> music when the doors were open to the dining room; I needed a relay
> closure for that task so the glue was more involved - but to feed a
> processor, converting the 6v 300Hz signal to a logic level is just a
> single NPN stage.
>
> Mounted high on the door frames, away from a mop or a cart, they have
> done fine.
>
> Tom
>
>------------------------------------------------------------------------
>
>No virus found in this incoming message.
>Checked by AVG Free Edition.
>Version: 7.5.516 / Virus Database: 269.19.0/1216 - Release Date: 9/01/2008 10:16 a.m.
>
>



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> ... Hopefully there is a NZ agent...

You must have some similar brand there, no? Are these not mandatory in
NZ like they are on American installations?
Tom



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I had an opportunity to measure the longest usable beam length of the
Genie photo sensor pair.

Source-to-sensor worked fine at about 50 feet, the length of the cable I
used, indoors. Although reliable, that distance seemed close to the
edge, and in sunlight the usable distance is probably less.

When the source and sensor are held together, both looking at a
retroreflector ( I used a common 4" plastic bumper reflector), the range
to the reflector is at least 20 feet, the limit of the test. The pair
was able to detect me walking by at four feet or so.
Tom



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