About optical sensor.

[Karkas]

Hello I make this new thread about the help requested in another one, I didn't
asked this questions in that because I didn't want to shunt the attention towards my questions while the questions that had to be answered were those asked by the OP, so this is the thread:

https://www.electro-tech-online.com/threads/need-more-help-with-sound-trigger.99492/

I would really like to know how would work a suggestion that they gave him, that was about using an optical sensor, I made not too long ago a proximity sensor, it was for beginners and with a not very long range of detection and I used an infrared LED and a phototransistor, and my questions is if would that sugestion be something like that, how would it work with a drop of water, I'm not working in a project about that right now, but I'm very interested in that and want to know how would it work.

Thanks.

 

[Mr RB]

You can shine the infra-red from LED to phototransistor. Then when the drop of water pass through it interferes with the beam and triggers the output. Clear water won't completely block the light beam but it will change it, so you need to detect a small change in signal at the sensor.

 

[Karkas]

But, wouldn't it be more complicated to locate the beam exactly where the drop is going to pass by? I mean the beam will be as thin as the drop, or can you find a thicker beam?.

 

[Sceadwian]

LEDs have upwards of 15degrees of beam width....tubes or optics over the receiver can narrow this reception pattern as much as you want. You can go from inches to MMs easily with the right optics, and it doesn't need to be complex.

 

[Karkas]

LEDs have upwards of 15degrees of beam width....tubes or optics over the receiver can narrow this reception pattern as much as you want. You can go from inches to MMs easily with the right optics, and it doesn't need to be complex.

Thanks Sceadwian, now I remember that when I made that project it was always indicating "proximity" and when I used my cellphone camera I saw the width of the beam, and I noticed that the phototransistor was always receiving the light even when no object aproached the device, those tubes you mention are black bodies?(blak bodies will absorbe that light, wont they?) did I need one for myu project to work right?
How do you get a larger distance of detection?

Thanks.

 

[Sceadwian]

It's just a tube....

Simple example, look at a parking lot.
Now look at it with your eye looking through a toilet paper tube...
Notice how the field of view suddenly limits itself?
This is pure plain and simple idiot proof physical mechanics.

The only thing that makes field of view and istance of reception seem magical or unobtainable by obscure methods is our failure to understand what is going on in the first place.

 

[Karkas]

Thanks Sceadwain, I understood.

 

[mneary]

Sometimes we paint the tube with black paint, often just so it looks better. If the inside of the tube is too shiny, it might accept light from a little bit off axis.

 

[Mr RB]

And even better than a tube is a black box with a entry hole and the sensor inside at the back, because it doesn't have tube "walls" to reflect. It might also easier to make than a tube...