I had some time since my last log and a lot of thoughts about the current setup.
One thing I thought about is lobes of the sensors. There is a HC-SR04 datasheet here, where this image can be found:
I guess, I will need a much broader directivity, at least for the sender.
Second thought: signal strenght.
Maybe a more powerful sender can enhance signal strenght on the receiver part.
This leads to the topic, I'll cover next: different sensor types.
I found some random sensors on e*ay.
First, I'll take measurements about their directivity and power then I'll make changes to my test rig.
After all I do want to believe that this project will succeed.
|Something I call "the cone"; with potetially very broad directivity. I have no idea, what this thing was used for, I could not find any datasheet.|
To measure directivity I created a small test-rig.
There is a sender-element at the end of the rail, connected to my red box. The rail has a wheel attached that can be rotated.
I guessed that eccentric mount does not affect the measurement a lot, so I mounted the sensors a little bit of centre, because it was easier this way.
I did modify the red box a little bit, so it can be connected to my scope.
So after all was set up, I took measurements of signal strength over several angles.
Blue is directivity of HC-SR04 and red of 'the cone'.
I'm very happy that I somewhat could reproduce the diagram from the HC-SR04 datasheet.
Earlier I did mention another sensor K-14WP10, this sensor will need a preamp which I didn't want to build right now. Therefore I just compared the two.
Just as said before, broad directivity is important for me, so next time I'll use 'the cone' for taking measurements.
In the diagram above each sensor directivity is normalized against its amplitude at zero degrees.
For 'the cone' aplitude at 0° is lower than the amplitude of HC-SR04.