Open Flow Meter

Update wiring diagram after finding a few errors when building some new units this month.

Thanks Hackaday for awarding my project the winner of the Earth Day Challenge 2021 https://hackaday.io/contest/176995-earth-day-challenge

The new calibrated version of the skit file is ready for download under V5 from our Gitlab.
We added meters per second to the display readout so now you can see both Kph and M/S.

Calibration with a commercially made flow meter:

In the image above we have the commercial flow meter on the left, a m/s to km/h conversion in the centre and the open flow meter on the right.

At first the open flow meter was providing a reading 4 times faster than the reading from the commercial unit, but after adjusting some settings both units give quite similar readings. Additional work needs to be done, however so far this will be more than good enough for GCSE, A Level and IB students usage.

The battery lid now fits better and the new version has been uploaded to: https://www.thingiverse.com/thing:4700913 Make sure to print the new version as the old version did not fit!

Here I leave the sensor in water for 24 hours to see if the silicon waterproofing of the electronics works.

When I switched on the control box and turned the prop, it still worked as before, so I'm happy enough with this waterproofing technique for now.

Here is the first fully assembled unit:

It features an: on/off switch, aviation connector, rechargeable battery, configurable intervals for taking speed tests and has a quick detach system from the ranging poll (this means we can carry less on field trips by using the range poll to hold the flow meter).

I tested a range of different pipe sensors at the start of this project back in April 2019:

I wanted to use the small clear sensor shown on the far right, however it could not measure slow moving water. The first sensor I built that was used for field work in a test was using the DN50 (the large black sensor, centre left of the image). But it still did not perform well in slow moving water.
The current build is now using the DN80, the one on the far left of the above image.