sensor to detect very tiny object in close proximity to other objects

Hello from Ontario Canada,

I am new to Arduino but excited to start on a new project idea

This project is focused on detecting very small objects.

I know ultrasonic sensors can detect proximity but my question is is it capable of differentiating between different objects?

i.e. can we have it to react differently to a specific very tiny object while there are other objects in close proximity?

the item is very tiny 3-5mm in diameter and the detection should be done from about 30-50cm where the sensor is held like a handset and pointed towards a box containing many items including the targeted small item but the target item might not be visible where is it exactly in the box.

This link is an example to show just the general “size of the item” and not the material or the technology… it is even smaller in the link but you get the idea

It could be made of items like foil, plastic, chip or anything, just need it to be specifically detected once under the coverage range of the sensor and don’t care if the sensor does not react to other objects at all.

There are some very tiny RFID chips but the detectors are very big and can’t detect from that distance and all that is really needed is to detect the presence of the small object and not read data out of it.

If this is not possible with an Ultrasonic sensor, would appreciate a pointer what sensor should be used for such project.


The ultrasonic sensor is going to give you the distance to the objects. It has a field of view, so it will give you the average distance to the sensing objects.

If you want to recognize the object you need to introduce some intelligent recognition. The ultrasonic sensor gives you back one distance not able to do many things later on. You can not compare the distance against other objects.

My suggestion is a sensor with different pixels, ideally a 3D camera (approx 250€). This type of camera will give you a matrix of pixels where each pixel is the distance to an object. In that case you are able to recognize objects or shapes.

Other sensors with less pixels and lower price could be:

Wavelength of 40 kHz sound is about 8 mm. Objects of the size you mention will not give much if any echo.

Besides that, there's indeed the field of vision, a cone of about 30°. The nearest object within that cone that gives a proper echo will be what your sensor records.

The Pixycam may be another solution. It is much cheaper than the prices mentioned in #1, it is designed specifically to work with Arduinos, but of course it has its own limitations. Read up on it to know whether it may work for your application.