First we want to thank the Hackaday jury members for selecting us as one of the twenty winners of the first round of the Hackaday Prize 2017. This is a great motivation and we will continue to work hard on this interesting project.
In addition to this good news, we finally found a solution to the problems we faced with the ultrasonic sensors.
We already made a funnel, with a wide diameter, but this turned out to be insufficient. In order to fix this we first made a funnel with a smaller diameter (see figure), but this did not have the desired effect as well. The walls of the funnels reflected the ultrasonic waves immediately, so a decent water level measurement could not be made.
We thought that the material of the 3D-printed instruments did not absorb the waves enough, which caused the too low values. Therefore we needed a sound absorbent material. The first thing that came in mind to test this was toilet paper. So we pasted some toilet paper on the walls of the funnels. Against all our expectations, this worked perfectly. In the video, one can see the results of the measurement, while the water level was increasing.
Besides the placement of toilet paper on the funnels, we also tried to place some toilet paper on the walls at the top of the pipe and use the sensor without any funnel. This turned out to work perfectly as well. Economically speaking this has even more advantages. It will be cheaper to place only an adsorbent material at the top of the pipe than produce a funnel ánd place an adsorbent material.
From now on we will look to find a more durable adsorbent material to place at the top of the pipe.