u/One-Cardiologist-462

I’m not squeamish when it comes to getting my blood drawn… but when you go to a lab, and the first thing you see on their waiting room wall is this, it kind of makes you think twice… 🤔

Today, I had an issue where I checkled under the sink and noticed that the waste disposal had a very slow leak.
After tightening the seal, I decided to implement a home made moisture sensor and warning system.
It essetially detects water by passing electricity throught the water to the gate of a mosfet, and then using that mosfet to pull current through a dedicated LED flashing chip.
A small test button is included, to test the battery works, though I do not anticipate the batteries draining very quickly.
As such, only zinc cells were implemented.

This has given me a good chance to put the dedicated LED flasher chip to good use.
After checking online, I think it's been discontinued.
I initially wanted to use a high brightness 5mm transparent red LED, but it wouldn't fit into place, so decided on a 3mm LED instead.

The LED can be changed by inserting it into the female wire ends.

As for the sensor itself, just a small square of stripboard with interleaved probe terminals.
Simple, but gets the job done.

All installed with tape and hot glue gun, for fast removal, if needed.
All mounted on a small peirce of card, for a quick and dirty job.

Strange failure mode of a linear halogen, I thought I'd share here, since they're a dying breed.
It seems that a break in the lead-in wire was causing a very short arc, which in turn caused the glass envelope to develop a severe hot spot.
Glass, when incredibly hot is actually conductive, but resistive, which further adds to the heating of that spot.
During the dim parts of the failure, one end of the glass envelope was glowing a deep red and the filament barely glowed.
This flickering went on for about five minutes before finally stopping and resting in a state of heated end glowing.
After a full power cycle and time to cool, the glass is no longer conductive, and the failure is complete - No more flicering or current passes.
The filament remains intact.

Nice and simple two transistor flasher, with a red and blue LED.
I kind of wish I had opted for warm white LED behind the colored lens, and that would have given a more natural halogen look.