follvalsch

follvalsch:

Teardown: Water Flow-Sensor

Recently the shackspace lasercutter started to act up a bit. Turns out that I’ve probably put a bit too much copper sulfate into the cooling water and it started to react with the aluminium connector pieces which then corroded and closed up on themselves.

However, after having just cleaned them, the lasercutter complained again that there was no flow. So this time around I suspected the flow sensor itself. Turns out I was wrong (it was the just recently cleaned connectors, again) but I took apart and cleaned the flow sensor anyway.

The sensor itself is genius in its simple design. It has a single moving part: a small flap that blocks flow in one direction but lets it pass with close to zero force in the other. The flap position is then detected, I’m going out on a limb here, most likely using a hall sensor or something similar.

What I also found is a piece of horrible engineering.
One side had a connector screwed in, secured with Teflon tape and a small O-ring. The O-ring was pressed to the casing by the face of the screw-in connector tube. So as soon as you start fastening the connector, the O-ring will inadvertently end up being squeezed into the tube and bunch up there, restricting flow and doing actually a worse job with water proving than if it simply wasn’t there at all.

Long story short, I’ve left out the O-ring entirely, put everything back together and it worked beautifully.

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