Cheapy DIY for fuel-starvation insurance...

There's a few turn-key product solutions you can spend couple hundred on and get a "bingo-fuel" warning system. They are a great, highly accurate and reliable backup to the gauges and I've heard good things about them. But it was a compelling and simple electronics project.



How they work... The sensors are a commodity item. You can get them online, I bought mine for $15 for three. Search for "Optical Liquid Level Sensor Switch". The physical working principal is that light refracts off of a liquid differently than a gas (air/vapor). The sensor is an all-in-one unit requiring a 5v source/ground and outputs either while in liquid it outputs no signal (low/ground) or in gas/air/vapor (high/5v). The unit I purchased came with a data sheet and claims it was capable of passing 10ma of current through it when triggered.

10ma is not a lot of current, but it could directly drive a small LED (relatively dimly) with a current limiting resistor. Pull 5V off your USB, one each of; sensor, led and resistor, a bit of soldering and that's it!

In my case I am going to connect them to one of the user-defined inputs in my G3X. It will show a FUEL-L or FUEL-R warning in RED on the PFD. But I also tried connected it to a ATTiny85 to drive bigger brighter LEDs and to test the sensors. That worked much better and wasn't at all hard.

As for mounting, I should have been more exacting... but I saw where others installed them and put mine in the same basic pace on the inboard baffle about 60mm from the bottom. I'll measure the fuel until the light goes off and placard the fuel valve with whatever that is... something between 2-4g I suspect.

Enjoy!

I've had similar thoughts but was going to use two- essentially to replace the float switch with a rougher, but more reliable "green/yellow/red" status to provide the "truth" info so I could compare to my fuel totalizer.

Aircraft Component Technology

What is old is new again. I have this system installed in 94 from Aircraft Component Technology. Don't think they exist anymore. The system is simple and works. The LED-s are mounted in the fuel sight glass. Here is a link to the documentation for those inclined to research further.

https://photos.app.goo.gl/A8aqdCoQ96JqKH4t5

Carlton

I can't see the image.

Is the sensor ok for use with fuel?

My only question would be if the sensors are approved for a explosive vapor environment.
G

sailvi767 said:

My only question would be if the sensors are approved for a explosive vapor environment.
G

Click to expand...

Looking at the docs for the Omega LV170, it is CSA approved when used with a zener barrier. However, this setup isn't exactly cheap at $135 for the sensor plus another $200-$300 for the barrier.

no pic seen

OPs pic is not visible.

If I were building one I?d port the light signals in and out via fiber optics, keeping all electricity out of the tank.

Why don?t you just set warning limits on your EFIS/EIS system? My old GRT WS system (at least twelve years old) allows one to define minimum fuel level for the fuel tank sensor and the fuel totalizer (different fuel measurement systems). I went to a lot of effort several years ago to calibrate the fuel floats to the EIS and they now read pretty accurate once you get below 16 gallons in each tank. In fact the lower the tank level the more accurate the reading. The fuel totalizer which reads fuel consumption is even more accurate in letting me know fuel remaining.

I have my L & R tank limits set at three gallons each and my Total Fuel limit set at eight gallons. When one of these conditions exists the EFIS will give a fuel warning. If I?m trying to cut it closer than those limits them my brain has obviously ?gone for a walk? and I will soon join it.

I assume the G3X has a similar limits setting capability.

I wear a swatch.