as the title may suggest, my intention is to create a measuring system that does not need very high accuracy and shall provide a fast result. To achieve that, I want to use a ultrasonic sensor.
Of course, there are easier methods but it should make some fun.
I drew a sketch how I thought it should look like (with Cabri 3D v2.1.2).
So the resulting distance is the full length (ca. 2 meters) minus the length that was measured by the ultrasonic distance sensor.
? Is there a problem that the sensor is very near to the bottom?
I am also planning to create a very similar device (actually the same, 90 degrees turned) that shall measure my body height. source (stick figure)
I want to attach this sensor near a wall. Is there a problem because the vertical wall then goes parallel to the emitted ultrasonic signal.
You will have no problem with a sensor positioned like that. But, ultrasonic sensors typically don't measure distances below 3cm accurately. In your second image I'm not sure if you meant to say 0.2 to 2 meters or cm (you wrote cm). But, if your second image is correct, and you want to measure from 0.2cm to 2cm, ultrasonic sensors won't work. If you typed it wrong, and are measuring 0.2 to 2 METERS, then you're golden. May I suggest using my NewPing Library which will allow for a very fast ping speed (other libraries can only ping once per second).
0.2 - 2 cm refer to the distance between the signal and the ground that is parallel to the signal's path. That's why I said in the title "attach an Ultrasonic Distance Sensor near the bottom". In the second picture, the light blue ray should depict the path of the ultrasonic signal which goes parallel to the bottom of the room. Is this also a problem?
And thanks for recommending the library.
0.2 - 2 cm refer to the distance between the signal and the ground that is parallel to the signal's path. That's why I said in the title "attach an Ultrasonic Distance Sensor near the bottom". In the second picture, the light blue ray should depict the path of the ultrasonic signal which goes parallel to the bottom of the room. Is this also a problem?
And thanks for recommending the library.
I see now. Nope, won't be a problem. I've tested plenty of sensors located on the ground (mounted to a breadboard). However, the sound "beam" is not like the blue line (not a laser). It broadcasts like how sound comes out of a speaker (because that's what it is, a speaker). But, it only needs to get a ping back and the close placement to the ground is of no consequence as it's not at a right angle to get an echo.
In any case, this setup won't be a problem at all.
karlok:
Ok, thank you very much.
And yes, it is a (almost) right angle where the signals should be reflected and so get its echo.
I will note that it really does need a right angle and something sound will bounce off of. It doesn't need to be a perfect 90% angle, and it doesn't need to be a big flat board. But, hitting a wall at enough of an angle or far away hitting something like a pillow will show no ping echo. Most objects are 3 dimensional so there's at least some part of the object that's fairly close to a right angle. But, if you wanted to trick the sensor, it would be fairly easy to make it fail. I don't think any of this is an issue at all to your project. You should be able to get very consistent readings with your setup.
