Best way to detect an object presence

Hello to everyone, just got here

I will try to explain what I need in the simplest way possible. Im designing a desk lamp, and we (me and the team) have come up with the idea of replacing a button with something more fancy. The lamp has an “O” shape, and the ligh comes form the inner side of the O. We were thinking of having some kind of sensor that detects when a human hand its placed in the middle, and that triggers the swich on/off.

What im looking for is the simplest and least bulky way of detecting that presence of the hand. Something that detects light, blocking of light, sound, anything. I have some ideas, but I want to hear your thougts. We are looking for something small, simple, and well, cheap :stuck_out_tongue:

[EDITED]
The “O” part of the lamp will be made of concrete, and a base at the bottom made of thermoformed plastic (its a Technology class project for the university, Im studyng industrial design). An arduino nano and a bluetooth board will be located inside the housing … Its one of the requirements that proffesors have determined. So we can use some kind of really small sensor in the “O” (we can´t drill or make more room there) OR we can put something bigger in the housing.

Thanks!

Capacitive sensing may be a way.

So, what are your ideas? What components do you have access to? Do you plan on using a whole Arduino just to turn on a lamp?

What im looking for is the simplest and less bulky way of detecting

Less bulky that what?

Switches work well.

What's your budget? The VL53L0x and VL6180X reflective time of flight sensors aren't cheap by hobby standards, but they'll do the job.

What about an infra-red break-beam sensor - just an IR LED on one side and a photo-transistor on the other side.

...R

Robin2: What about an infra-red break-beam sensor - just an IR LED on one side and a photo-transistor on the other side.

...R

I second this. very easy and very cheap. One down side might be, if the lamp is in direct sunlight the IR sensor might become saturated and falsely trigger the switch. Maybe this can be figured out in code.

Thanks for your replies!

INTP: So, what are your ideas? What components do you have access to? Do you plan on using a whole Arduino just to turn on a lamp?

The lamp will have an arduino nano and a bluetooth board... Its one of the requirements that proffesors have determined (its a project for the university, Im studyng industrial design). So we have part of the hardware already there.

larryd: Switches work well.

Indeed. But it would break the conept we are trying to achive. We are looking for something more minimalistic and "magicness". We have considered puting a normal switch behind a plastic housing, though. We call that the plan B (The lamp its kind of an "O" made of concrete, with a base at the bottom made of thermoformed plastic. Its a Technology class project).

mikb55: What's your budget? The VL53L0x and VL6180X reflective time of flight sensors aren't cheap by hobby standards, but they'll do the job.

Mmm yeah, that would be to expensive, at least where I live (Argentina).

-> So IR LED + IR break-beam sensor OR capacitive sensor: This would be the options, right? I have access to that kinda stuff in the local stores. Any other suggestion or recomendations? I realice now that there was important info missing in my first post

Ill definitely have to show you the final result when its done, you are being very helpfull!

I don't think a break beam is even necessary. Put both components on the same side and let the hand reflect. Same as on all those LED coffee tables. The simple modules I've built that were purely analog in design, only required a handful of components. With an MCU, an IR LED and an IR photodiode with a few resistors and you'll have a very rudimentary proximity sensor perfectly suitable for your project that will be easier to hide if you put them next to each other and use reflection instead of break-beam config.

A ring wire through your lamp (you say it's a circular one) may work really well for capacitive sensor. They can be made really sensitive (look at how a theremin works). Least bulky for sure, but stands and falls with proper grounding.

INTP:
I don’t think a break beam is even necessary. Put both components on the same side and let the hand reflect. Same as on all those LED coffee tables. The simple modules I’ve built that were purely analog in design, only required a handful of components. With an MCU, an IR LED and an IR photodiode with a few resistors and you’ll have a very rudimentary proximity sensor perfectly suitable for your project that will be easier to hide if you put them next to each other and use reflection instead of break-beam config.

That would be a good option then! The only disadvantage I see is that it would require to make two small holes in the housing to let the emmiter and reciever work. Or maybe we find even a better way of hidding it.

wvmarle:
A ring wire through your lamp (you say it’s a circular one) may work really well for capacitive sensor. They can be made really sensitive (look at how a theremin works). Least bulky for sure, but stands and falls with proper grounding.

Well Its acctually almost an O, its open(“cutted”) at the top. A curvy “U” would be a better description. Could your idea work anyhow?
Reference image, without the plastic piece:

Should work just fine. In the end it's just a kind of antenna. Do look up how such sensors work, or try to build your own Theremin then integrate it into your lamp!

As I said, they stand and fall with proper grounding - as otherwise the whole object's potential will start floating.

You won't get much smaller than SMD components if you go with IR. But since you have a bunch of circuitry elsewhere, a capacitive wire working as an antenna would be less obvious even though it'd be bigger in a way. Capacitive is going to need some fine tuning, though. Play just with an Arduino and the capsense library and read that guide to get started.

The lamp will have an arduino nano and a bluetooth board

So where is the Bluetooth content of this project? What sort of Bluetooth is is BLE or normal? They are not interoperable.

Hello to everyone! I just wanted to come by and say thanks for all the answers you gave me. The proyect was a success! Not only the pieces of concrete and thermomolded plastic ended up well, but the control system “without a button” works smoothly.

I used an IRED and a phototransistor, mainly because of the cost. The process of removing all the backgroud IR radiation turned out to be quite a headache. I had to learn a lot of programming, light properties and signal detection. Through several test and iterations of the code, we have finally archieve a detection failure rate of less than 1% even while being exposed to direct sunlight or light changes.

A couple of images:
https://photos.app.goo.gl/oJSo5YtxEKSHrgZRA
https://photos.app.goo.gl/tg1w2U5HkNqz9U8F9

A video!
https://photos.app.goo.gl/WfiW6NE8WBJ4H8UNA

Well, I thinks thats it. I felt the need to share it with you beacuse you were really helpfull! :slight_smile: