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.
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...
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..
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...
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!
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 ;(