Re: Optical Sensor (different from the 2-d sensor)

Howhurley wrote:
On Jul 7, 3:05 pm, Tim Wescott <t...@xxxxxxxxxxxxxxxx> wrote:
Howhurley wrote:
Hi again. I am looking for an optical sensor, probably LED based,
maybe laser diode, that can be mounted on a thin PCB. It needs to be
fairly small. I am designing a small retroreflective system from
inside a slot machined into a molding with a piece of reflective tape
approx 3 ft away.
Any takers on this one?
LEDs and lasers both emit light.

Do you mean you want a sensor designed specifically for use with a
retroreflector?

You're probably stuck with using a PIN photodiode and LED, and doing
your own optics.

But your request is so vague it's impossible to tell.

How bright are the other lights in the room? How many of these devices
will be in the room working together? Does it have to work while
looking at it's brother right next to the reflective tape? How wide is
the slot? How much accuracy can you pay for? Etc.

--

Tim Wescott
Wescott Design Serviceshttp://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details athttp://www.wescottdesign.com/actfes/actfes.html

I want to project an LED or laser beam perpendicularly out of a .33
inch aluminum slot. I want to "see" the reflection from reflective
tape. up to 3 ft away and tell when the beam is broken. I was
thinking that I could modulate the frequency of the transmitter and
use a uP with the capability to have a fairly small window so I can
eliminate extraneous "noise."

I probably could put the detector on the opposite side instead of the
tape.

I was also thinking, if I did that, I could use a couple line
collimated lasers, frequency modulated, so an individual reciever
would be able to tell if the source was interrupted.

Thanks again for your response.

Sorta like the ones you can buy from Radio Shack, only smaller?

Should work.

I would try first with an LED or laser + a PIN photodiode. If you _really_ want to distinguish your signal from others you'll use a pseudo-noise sequence to turn the thing on and off; if you're sane you'll just use a fixed tone and hope that there's nothing else in the room on frequency.

You may have more of a challenge minimizing the coupling between the transmitter and receiver with no reflection than you do with anything else.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html
.

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