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Topic: Simple IR retro-reflective sensor for a 3v arduino (Read 162 times) previous topic - next topic

GeorgyCarastas

Hi guys!

I don't have a lot of experience with electronics, just following and adapting schematics.
I adapted this retro-reflective sensor schematics https://create.arduino.cc/projecthub/mova2/long-range-beam-break-sensor-with-reflector-panel-4dfc48 into something that works at 1.5 meters.

I played with the LED resistor to limit the power and work at 1.5 meters. But now, if an object passes too close to the emitter / sensor box it reflects back and does't break the IR barrier.
Also, I'm using reflective tape to reflect the beam on the wall.

I use a SFH4545 LED and a TSSP4038 receiver and it works 90% of the time, except when something smooth like a hand or something closer passes.

I was thinking of trying a TSSP4P38 for it, but I'm not sure, I see that it's used as more of a distance mesurer without a reflective surface. I really want to use the reflective tape because I'm afraid it will reflect from the wall or something.

Thank you for anything!
George

zwieblum

You'll need some optics to make it work as expected.

If you are interested in the IR emitted, you cyn darken the room and use a ccd camera. It'll show you the IR light on the objects.

GeorgyCarastas

#2
Nov 19, 2019, 09:08 pm Last Edit: Nov 19, 2019, 10:03 pm by GeorgyCarastas
Thank you!

What do you mean by optics? Polarizing filters? I don't understand how that would work...

Thanks,
G

Paul__B

You need to laterally separate the emitted beam form the returned beam.

GeorgyCarastas

Thank you, the receiver is in an aluminium tube, it does not get light directly from the LED, I've made a drawing of the problem! ;)

G

DrDiettrich

Why do you think that an object breaks the beam, instead of reflecting it?

What does "break" mean here? The beam must either be absorbed or be reflected or scattered into some different direction. If an object does not behave this way, it won't break the beam.

An apparently "dark" object does not necessarily absorb IR, even if it absorbs visible light. The same for apparently reflective material...

Wawa

Transmitter/receiver opposite each other should work more reliable,
since you don't have the problem of the object reflecting IR as well.
You can also get greater distances with two units opposite each other.
25 meter in broad daylight (without optics) should not be a problem.
Leo..

GeorgyCarastas

Why do you think that an object breaks the beam, instead of reflecting it?

What does "break" mean here? The beam must either be absorbed or be reflected or scattered into some different direction. If an object does not behave this way, it won't break the beam.

An apparently "dark" object does not necessarily absorb IR, even if it absorbs visible light. The same for apparently reflective material...
Because in 90% of cases it "breaks", scatters or absorbs the light.
And off the shelf retro reflexive sensors work like that very reliably, even from a small distance. But the problem with them is that they are too big and they need 12v to power, and they don't fit in the nice little case I plan to use, and need a step-up from the usb 5v I'm using, and are expensive.

I'm just kinda hoping that there is a simpler solution, like some specialized LEDs and sensors. Fingers crossed!

G

zwieblum

Well, use a Sharp IR distance sensor, looks like that thing has built in what you want to get.

GeorgyCarastas

Hi, thank you for your suggestion, I tried with a Sharp IR and it worked great! Now I just need to figure out how to use it with a Wemos D1 without dropping the wireless connection ;(

Thank you!
G

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