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.
HC-SR04 |
K-14WP10 |
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. |
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Edit1:
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.
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Edit2:
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.
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