Quote Originally Posted by n85ae View Post
There's a bunch of essentially the same sensor on Amazon [...] I believe they are all the same, just sold by different vendors.
I don't mean to start an argument, but that's bit like saying an Arduino is the same as a PIC, or an MSP430, or an ESP32. Similar shape and broadly similar operating principle doesn't make them the same. Shenzhen alone is awash in electronics manufacturers, let alone the rest of China.

I'm comfortable giving this sensor a try, as both examples I purchased (separately) have worked reliably in my bench tests.

I may end up doing a two sensor, with mini Arduino with high/low, and a comparator logic for determining a fault condition. This way if for example you had a continuous high on one, and low on the other it could be flagged as a fault condition.

So - LED/ON - Low fuel. LED/OFF have fuel. LED/Blinking - Fault condition.

Or maybe use a tricolor LED, and make it Green=good, Red=low fuel, blinking amber = fault.
Something like this...
Yes, that would certainly work. Without diagramming it, I suspect an analog comparator, some logic gates and an oscillator could do that without needing any software. If you use an Arduino (or any μC), be sure to have some means of heartbeat/watchdog monitor. They all lock up sooner or later, and if it happens with the green light on...

Be sure to test your sensors on the tank. Mine are sensitive to position and don't work if they're too close to an edge or corner.

Modern aircraft designs using a "dark cockpit" concept would prefer your first indication option: when all is well, there are no lights illuminated. I would consider swapping the On and Blinking indications. It's more important that the low fuel indication get your attention than the fault condition. That said, this is experimental aviation!