New Low Fuel Alarm Sensor

[n85ae]

The amazing thing about the Forum, is the amount of overthinking that goes into turning on a light

More amazing is - Arduino's, because you can do simply things simply. The time required to do things
with microcontrollers before they came along, was horrible. Now people can just make things, simply,
and they work.

Jeff

[Eric Page]

If anyone is still following this saga, I finally got back to it this morning and assembled revision 2. Everything works as intended, so I'm calling it done.

There are still two versions. One is for EFIS-equipped aircraft: it provides 12V to its output during normal operation and pulls its output to ground in a low fuel alarm condition. The other is for non-EFIS-equipped aircraft: it flashes an LED during a low fuel alarm condition. Both have press-to-test capability if installed as shown on the schematics.

For either version, you'll need a DS1603NF ultrasonic liquid sensor. They're available for <$30 from numerous vendors on Amazon, eBay or AliExpress (search links). See the first post in this thread, above, where I discuss sensor position on the header tank.

For EFIS-Equipped Aircraft

EFIS Interface.jpg

Schematic/Wiring Diagram: Sensor Interface Rev A3 (EFIS).pdf
Circuit Board: https://oshpark.com/shared_projects/sGUSk5Rn (click Actions > Order Board)
Components: https://www.digikey.com/short/p0t3pqw3 (link opens a populated shopping cart)
Momentary Pushbutton Switches: https://www.digikey.com/short/4tv9dz

For Non-EFIS-Equipped Aircraft

Non-EFIS Interface.jpg

Schematic/Wiring Diagram: Sensor Interface Rev C2 (Non-EFIS, Flasher).pdf
Circuit Board: https://oshpark.com/shared_projects/21g619xZ (click Actions > Order Board)
Components: https://www.digikey.com/short/9nm2m4ww (link opens a populated shopping cart)
Latching Pushbutton Switches: https://www.digikey.com/short/4tf58w
LED Bezels: https://www.digikey.com/short/4tfbjb

The two slots in the end of both circuit boards are for a small zip tie to strain-relieve the wires. Put the wires through a short length of shrink tube, solder the wires to the board, slide the shrink tube up near the solder joints and shrink it, then use a small zip tie around the wire bundle and through the slots. This works best with the head of the zip tie on the back of the board.

The new LED that I bought for the non-EFIS version is much brighter than the illuminated switch I tried before. It will be easily visible in sunlight, especially if mounted in front of the pilot. This photo doesn't do it justice.

New LED.jpg

Due to ordering minimums I have a few extra boards of each type, which I'm happy to give away. They're fully assembled and the non-EFIS boards will include the bright red LED and a chrome mounting bezel.

If you'd like one, please send me a private message indicating which type you need and your address, and I'll put one in the mail. First come, first served. You'll still need to buy the ultrasonic sensor and a pushbutton switch (see links above).

I'll post here again when they're gone.

[Eric Page]

All of the non-EFIS boards are spoken for. As of this posting, I have 3 EFIS interface boards remaining.

[Eric Page]

All of the remaining EFIS interface boards have gone to new homes.

Please see the links in Post #36, above, to purchase blank circuit boards and components to assemble either type of interface.