Block the return wave of ultrasonic sensor

I am trying to develop a system with Arduino and an ultrasonic sensor. The process that an ultrasonic sensor like the hc sr04 follows is:

  1. Send a wave (trigger signal).
  2. It hits the object.
  3. It returns to the module via a reflected wave (echo signal).

I want to block the reflected wave if the trigger wave hit a specific object so the Arduino don't read any echo signal or read a high distance (not the real distance to the object). I am trying with acoustic isolation but it's doesn't work. Can anyone help me please?

Can't you simply unsolder the receiver transducer?

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But i need the sensor work with other objects. I want to block only if I use a specific object. I am trying to know what kind of product do that

How is the sensor supposed to recognise a specific object?

Something like the isolation sound panels that have music studios. I think this panels block the sound no?

The panels absorb the sound rather than blocking it. Can you cover the object(s) that you want to ignore in ultrasound absorbing material ?

…or simply ignore returns that are closer or farther than the desired range.

Perhaps

The distance to the object is always variable :frowning:

So, it’s impossible to discriminate between a real echo, and an unwanted ping…

Think it through a bit more.

Sounds like xyproblem to me. What are you trying to achieve? What is this "specific object"?

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Using ML to train models?

Though with a 15 degree detection cone what's a wall machine model over what a box machine model might not be so discernable.

I want to detect the presence of a person (like his arm, finger...) without touching nothing (but it can wear anything). I tried RFID system with tags but in the industry it have coupling issues. Problems also occur with inductives and capacitives sensors

So where does the need to ignore some objects arise ?

You want to differentiate between an arm and a finger with using a sensor that has a 15 degree detection code?

I use 2 AMG8833's and Linear Regression to detect people from 15ish feet away.

The idea is that the ultrasonic sensor will works normally with other object like a bottle, folder... but when a person or any part of her body stay in front of the sensor it will not receive a reflected echo signal, so it will detect that there is a person there. A vision system would be really expensive :frowning:

I'm going to look into it. Thanks!

If no reflection is received then how will you differentiate between a person being there and nothing being there ?

Because it is always pointed at an area within the measuring range, i.e. it is continuously receiving a normal measurement value.

Have you tried this

RCWL-0516 Microwave Proximity Sensor

google it. They work well for detecting people.

Otherwise, ask all your people to wear ultrasound absorption clothings.

a7