Re: Damned Projects!

On 12/27/2024 1:02 PM, Cursitor Doom wrote:

On Fri, 27 Dec 2024 11:12:19 +0000, Cursitor Doom <cd@notformail.com>
wrote:
 

On Fri, 27 Dec 2024 08:30:05 +0100, Arie de Muijnck <noreply@ademu.nl>
wrote:
>

On 2024-12-27 02:21, Cursitor Doom wrote:

On Thu, 26 Dec 2024 15:09:38 -0800, john larkin <jl@glen--canyon.com>
wrote:
>

On Thu, 26 Dec 2024 19:29:11 +0000, Cursitor Doom <cd@notformail.com>
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

>
Tell us about your design.
>
I recall a water detector made from a clothespin and an aspirin and a
couple of pieces of wire.
>
But it doesn't take much current to turn on a mosfet.

>
True, and that's what my design relies on. I say "design" but that's
over-dignifying it. I doubt there's more than 10 components to it all
told - tops! Still, the most important thing is it works.
How did the pin/aspirin desgin work??

>
>
https://ademu.home.xs4all.nl/download/Waterdetector%20without%20headache.jpg
>
Arie

>
Ingenious!

 Just for a bit of fun (which I don't get much of at my age) I thought
I'd replicate the idea to see how effective it is. My first attempt
didn't work out at all, as the clothes peg compressed the (soluable)
aspirin as it became saturated and prevented it dissolving
sufficiently for the gap to close. I was left with about a tenth of an
inch between contacts.so FAIL!

The sensor I made is simple and reliable.
Etch a board with two "combs" where the
tines of the combs interlace, like this:
+-+-+-+----o
| | | |
||||||||
  | | | |
  +-+-+-+---o
When water drips onto the sensor, the open circuit between
top and bottom "combs" goes to a resistance, in my case below
100K and sufficient to drive an NPN and operate a relay.
Ed

For this to stand any chance of working, you'd have to fashion the
contacts so they have pointy ends. That should work, BUT if it were
used in my applcation, several dozen gallons of water would be all
over the floor before it would be able to close-up. My design, OTOH,
shuts off the electric in about 25 femto-seconds. :-)