Re: Damned Projects!

See addendum at bottom.

Wanderer wrote:

Cursitor Doom wrote:

Gentlemen,
>
I'm currently in the process of building a device which will shut off
the power to a washing machine in the event of a hose failing and
spewing water out all over the floor. This is an eventuality which has
always caused me considerable angst, so I finally decided to do
something about it. After all, those flimsy 'exhaust' hoses go brittle
over time and having one split 'in action' could cause a significant
amount of damage to the surrounding area in a very short time. Having
something to cut the power off instantly as soon as the water hits the
floor would be a very worthwhile addition to the utility room and
beyond.
I came up with a pretty simple design which I've already proven to
work first time at the breadboarding stage. However, turning this
concept into a practical proposition is taking *far* longer than I'd
imagined. I am getting there, but *slowly* and was wondering whether
other people here have the same sort of problem as I invariably do
with these little personal projects they undertake?
>
Your hydrophobic pal,
CD
>

>
The way I've seen water detectors done is with an LED angled to reflect off
a piece of glass to a photodiode when the glass is dry. When the glass is wet
the index of refraction of the glass/water is different from the glass/air and
allows the light to pass through and not hit the photodiode. That's how automatic
windshield wiper raindrop detectors work.

Here's the physics of a rain sensor:

<https://www.yoctopuce.com/EN/article/how-to-build-a-rain-sensor>

When you rotate this sensor on its side it ought to work:

<https://www.instructables.com/Measuring-the-Refractive-Index-of-Liquid-at-a-Defi/>

If it's high enough, you probably can fabricate (print) it as a single
piece and leave the cover off altogether.

On the other hand, a cover does keep the dust out. Accumulated dust appears
to be the bane of a refractive water sensor.

Danke,

--
Don, KB7RPU, https://www.qsl.net/kb7rpu
There was a young lady named Bright Whose speed was far faster than light;
She set out one day In a relative way And returned on the previous night.