IR LED tx/rx for object detection

[engineheat]

Hi,

I need a quick and dirty way to detect the presence of a small black matte object, using Arduino

I want to try using a IR LED like this:

and the corresponding receiver:


The object moves along a fixed track. At the location of interest, I plan to orient the two LEDs (tx/rx) facing each other, and if the object blocks the IR ray, the Arduino would get the signal.

The challenge is that the object is small (2mm diameter). It's too small to block all the IR light. To better "focus" the IR beam, I want to build a conical opaque "cover" to the transmitting LED with a tiny 1mm or so opening so that the object can fully block the IR ray. Is this a good approach?

Thanks

[engineheat]

Hi,

I need a quick and dirty way to detect the presence of a small black matte object, using Arduino

I want to try using a IR LED like this:

and the corresponding receiver:


The object moves along a fixed track. At the location of interest, I plan to orient the two LEDs (tx/rx) facing each other, and if the object blocks the IR ray, the Arduino would get the signal.

The challenge is that the object is small (2mm diameter). It's too small to block all the IR light I'm afraid. To better "focus" the IR beam, I want to build a conical opaque "cover" to the transmitting LED with a tiny 1mm or so opening so that the object can fully block the IR ray. Is this a good approach?

Thanks

[wraper]

Is it possible to use photo interrupter sensor like in mouse wheel? How big distance there should be between emitter and receiver?

and the corresponding receiver:

It's not something you should use. It's for IR remote control, way too sensitive so will catch even reflections from walls and needs signal to be modulated at certain frequency.

[ledtester]

A photo interrupter like wraper suggests is a better approach.

You want to shield the detector so that it can only receive light from the emitter.

https://www.rohm.com/electronics-basics/photointerrupters/what-is-a-photointerrupter

The detector is a simple photo-transistor.

In a pinch you can use an LED:

https://wiki.analog.com/university/courses/electronics/electronics-lab-led-sensor

and there are a bunch of videos on youtube demoing this -- i.e. search for "using an led as a light sensor"

[jackthomson41]

I would suggest you to simply use ultrasonic sensor HC-SR04, with IR Proximity Sensor in Proteus you need to interface both receiver & transmitter while in ultrasonic sensor simply plug trigger and echo pin and detect the object.

[mikerj]

I would suggest you to simply use ultrasonic sensor HC-SR04, with IR you need to interface both receiver & transmitter while in ultrasonic sensor simply plug trigger and echo pin and detect the object.

How on earth do you think a 2mm object is going to be reliably detected via ultrasonic sensors of that size? 

[Gyro]

Is it possible to use photo interrupter sensor like in mouse wheel? How big distance there should be between emitter and receiver?

and the corresponding receiver:

It's not something you should use. It's for IR remote control, way too sensitive so will catch even reflections from walls and needs signal to be modulated at certain frequency.

As you can see from wraper's photo, the interrupter sensors have a narrow slit in front of the IR receiver. Without this, you're unlikely to be able to cleanly sense a 2mm diameter object. With just an LED and phototransistor you'd probably just see a minor dip in amplitude.