Re: Damned Projects!

On 28/12/2024 12:39 pm, Wanderer wrote:

On 2024-12-26 14:29, 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.

That's elegant. Transparent plastic would work as well, and might be less brittle. the theory is well understood and has some subtle aspects.
https://en.wikipedia.org/wiki/Total_internal_reflection
--
Bill Sloman, Sydney