New Low Fuel Alarm Sensor

[Eric Page]

In an earlier thread (http://teamkitfox.com/Forums/threads/3532-Low-Fuel-Sensor), we discussed existing low fuel alarm sensors, and I mentioned that I found an alternative that might work. It's an ultrasonic liquid sensor that detects the presence or absence of fuel by shooting high-frequency sound pulses through the wall of the tank and measuring reflections. I bought the sensor from this Amazon listing (https://www.amazon.com/gp/product/B0836D8RP1/), which was the lowest price I could find, by half.

The sensor is 1.1" diameter x 0.75" thick. It has an 18" long 4-conductor pigtail with a 4-pin connector (JST XH-series (https://www.digikey.com/short/z0b8pb)). The four wires coming from the sensor are:



[*=left] black (ground)
[*=left]red (12V)
[*=left]yellow (active high output)
[*=left]white (active low output)


When the sensor detects liquid, the active high output provides 12V and the active low output pulls to ground. It comes with three small plastic vials containing acoustic gel for testing, epoxy resin for mounting and hardener for the epoxy.

26115 26114

I plugged most of the bungs on a Kitfox aluminum header tank and filled it ~3/4 full of water, then I mounted the sensor to the back of the tank with acoustic gel and tape. During testing I tilted the tank along the plane of its back face to move water behind the sensor. The sensor is rated for a power supply of 10-36V. I powered it with 12V from a bench supply and it consumed 13 milliamps (0.013 amps).

It doesn't like to be mounted near the edge or corners of the tank; I'm guessing that the extra metal in those locations interferes with sensing. After some trial and error, I ended up mounting it ~2" down from the top edge, between two of the top-side bungs. In that location it detected changes as I tilted the tank very reliably, and I never saw it miss. Sensing a change of state takes about one second, at most.

From my testing, I'd say it's a winner. It's dirt cheap, it's small and lightweight, it mounts outside the tank and it doesn't require an additional tank, hoses or fittings. I'm going to go ahead and use it. I'll design a small interface board to make it easy to connect to ship's wiring. Once that's done and tested, I'll post details in case anyone else is interested.

One note: I don't know that the sensor location I tested is feasible once the tank is mounted to the airframe, so I'm planning to mark areas with no interference on the tank and re-test, when I get to that point.

[rv9ralph]

The sensor you found has promise. My question is what are you using to display the reading. I have a simple, few electronics panel.

Ralph

[Jerrytex]

Good Deal! I was hoping it was going to work out.

I'll be ordering one soon.

[Russell320]

How long will the acoustic gel remain in place after installation?

[Eric Page]

How long will the acoustic gel remain in place after installation?
It's only used for testing. Permanent installation is with the provided epoxy, though I suspect that a thin skim of Hysol would work just as well.

[Eric Page]

My question is what are you using to display the reading. I have a simple, few electronics panel.
I'm going to use an alarm input to a Dynon EFIS, but using the sensor with an old-school instrument panel would be pretty easy too.

I didn't mention it in my first post, but I plan to design two versions of the interface board to use with the sensor. One will be very basic, to support EFIS inputs, and the other will incorporate a dead-simple LED flasher circuit for less complex panels, like yours.

I'll post more on those once I've designed and tested them, but it'll be a little while. I'll try to keep the assembly as simple as I can; I know some folks aren't very comfortable with board-level soldering.

[CoClimber]

I have two of these, one for each wing tank. I'll install warning lights on my, yet to be built, panel. I have a float switch for my header tank to tell me that I really messed up with fuel management.

[avidflyer]

I ordered a couple of them. One for a spare. I'm thinking running to a small green LED light for full header tank, and a red LED light for low fuel in header tank. Thanks for posting these sensors up. JImChuk

[n85ae]

There's some Arduino circuits out there for using with that sensor. But for header you only really need to know
continuous low fuel, since the header always has a bubble in it working out exact volume would not be of much
value

Jeff

[avidflyer]

I ordered a couple of them. One for a spare. I'm thinking running to a small green LED light for full header tank, and a red LED light for low fuel in header tank. Thanks for posting these sensors up. JImChuk

The header tank should always be full of fuel I would think under normal situations. I would have the sensor as high as possible on the header tank. And as I understand this sensor to work, is it will send current down the one wire if the sensor is reading fuel. That in my thinking would go to the green light, which will maybe also tell me everything is working with the sensor. If header tank starts to run empty, the sensor should then send a current down a different wire to the red warning light. Maybe I've got it all wrong, but that is what my plan was based on how I thought it could work. Am I wrong? JImChuk

[Eric Page]

Am I wrong?
A bit, yes. When there's no fuel detected, both outputs are high impedance, or floating (OFF). When fuel is detected, both outputs are active (ON). The active high output (yellow wire) provides 12V (or whatever voltage the sensor is powered with), and the active low output (white wire) pulls to ground. That's the important point: with fuel present, both outputs are ON; with fuel absent, both outputs are OFF.

If you want to light an LED when fuel is present, simply connect it to the active-high output with an appropriate current-limiting resistor (R):


R = [supply voltage - LED forward voltage] / desired current


For example, a typical green LED will have a forward voltage of 2V at 20mA. So, for a bus voltage of 14.4V...


R = (14.4 - 2) / 0.02 = 620Ω (a standard value!)


26136

This will indeed confirm that the sensor is working. However, when fuel is absent, both outputs are OFF, so it won't send current to your red LED.

If you want to light the red LED when fuel is absent, you need to invert the active-high output to obtain 12V when it's OFF. The simplest way to do this is with two components: a resistor and a P-channel MOSFET. That circuit looks like this:

26137

When the active-high output is ON (fuel present) the MOSFET's gate (labeled "G") is driven to 12V by the sensor, and when the gate is at the same voltage as the source (labeled "S"), a P-channel MOSFET is off. When the active-high output is OFF, the 10kΩ resistor pulls the MOSFET's gate down to ground, which turns the MOSFET on, allowing current to flow, lighting your LED (you still need the current-limiting resistor above). The 10kΩ gate resistor value isn't critical. It just needs to be high enough to limit current through the sensor output when it's ON; anything from 1kΩ to 100kΩ will work fine.

So, if you want two LEDs, green turned on when fuel is present and red turned on when fuel is absent, the circuit looks like this (again, LED current-limiting resistors not shown):

26135

Now, with all of that said, I should point out that virtually all aircraft manufacturers these days adhere to the "dark cockpit" concept, which means that no indicators should be lit when systems are operating normally. So, your green LED would not be installed. In any case, the fact that the engine is running makes it kind of redundant.


As I mentioned in an earlier post, I'm designing a small interface board to connect between the sensor and a warning indicator. It will actively hold the LED off when fuel is present, and flash it when fuel is absent. It may also have a press-to-test function to confirm that the flasher circuit is working. If you press the test button and the LED flashes, then goes off when you release it, both the sensor and the flasher are working. Using an illuminated pushbutton switch would incorporate both the warning indicator and the press-to-test function in one panel hole.

It may turn out that the sensor outputs are OFF when it's first powered up, and it takes a couple of seconds to self-calibrate and detect fuel in the tank. In that case, the press-to-test feature would not be necessary because the warning indicator would flash briefly each time the master switch is turned on. This would confirm that the flasher and LED are working, then when it stops, you would know that the sensor works. The switch could instead be used to de-power the circuit, eliminating distraction during a genuine fuel emergency.

Anyway, that's enough middle-of-the-night thinking out loud. More testing to be done. Stay tuned...

[avidflyer]

Thanks Eric for the information you provided. The LED lights I have run on 12 volts, so they must have a built in resistor. https://i.ebayimg.com/images/g/VdoAAOSwMzVbvjIe/s-l300.jpgBecause I'm electronically challenged, If you don't mind, how do I wire up one of these for a low fuel alarm in the header tank? That would be one red led that would light up on the panel if the sensor sees no fuel at it's height in the tank. Thanks, JImChuk

[Eric Page]

The LED lights I have run on 12 volts, so they must have a built in resistor. Because I'm electronically challenged, If you don't mind, how do I wire up one of these for a low fuel alarm in the header tank? That would be one red led that would light up on the panel if the sensor sees no fuel at it's height in the tank.
If your LED came with a resistor, then you won't need to add one. In my last post, above, I explained how to light the LED when the sensor doesn't see fuel. Do you have a specific question about the circuit that I can help you with?

I would recommend that you test your LED in bright sunlight to see if it will be bright enough to get your attention immediately. Most small indicator LEDs like are shown in your picture are meant to be used on a control panel, indoors. They're not very bright, and their small size makes them even less likely to be noticed, especially if they're not flashing.

[avidflyer]

Well I ordered some of those Mosfets. Not sure how to tell which wire connects to what leg on the Mosfet, but maybe that will become apparent when I see them in person. Like I said, I'm very much electronically challenged, and not at all afraid to admit it. Thanks again Eric, JImChuk

VP2106N3-G Microchip Technology | Mouser (https://www.mouser.com/ProductDetail/689-VP2106N3-G)

https://www.mouser.com/images/mouserelectronics/images/A_TO_92_3_t.jpg

[Eric Page]

The product page on Mouser has a link to the datasheet. The first page shows the pinout.

It's not my place to tell you your business, Jim, but I think you're jumping the gun a bit. As I've said a couple of times, I'm working on an interface for the sensor that will take care of flashing an indicator and will be able to confirm that the sensor, flasher and indicator are all working before each flight. It'll be built on a printed circuit board that can be neatly packaged in heat shrink for protection and easily tied into a wiring loom.

I'm going to post links to sources for everything so that anyone can buy the parts, including a custom circuit board, for around $50 total, and potentially less if you don't like my choice of switch/indicator. The circuit will be all through-hole parts, so assembly will be no more difficult than an electronics starter kit. I'm looking at two versions, for EFIS and non-EFIS equipped aircraft.

If there's enough interest, I might even assemble a batch for forum members as a one-time deal, for the cost of parts and postage.

But, hey, it's your airplane!

[avidflyer]

Thanks Eric. Not unusual for me to jump the gun. But I guess I missunderstood the whole works right from the beginning. I'll keep an eye on what you come up with, but of course in the meantime, I've got these parts.....JImChuk

[Eric Page]

I've got a little more testing data to share. This time I placed the sensor where it would see fuel from the moment power is applied, and measured the delay from power-up until the output reflected the presense of fuel.

In this image, the yellow trace is the 12V supply to the sensor and the blue trace is the active high output. Each vertical division is 2V and each horizontal division is 0.5 second. At the left edge, both traces start at 0V. Power is applied where the yellow trace rises to 12V, then 2.5 seconds later, we see the output rise to 12V as well. This result is very repeatable; it looks exactly the same every time I run the test.

26171

This is the result I was hoping for, because it means that the sensor's output will briefly simulate a low-fuel condition at power-up, allowing an automatic self-test of the whole system. When the master switch is turned on, the indicator will flash for 2.5 seconds, then normal sensor output will begin and the indicator will go dark. If any of that doesn't happen, you'll know there's something wrong.

More to follow...

[CoClimber]

Looks like you posted more then deleted the post. If you want, I could go over what you have and review it. I am an electrical engineer and specialize in this sort of thing.

[Eric Page]

Yeah, I did. I guess the server must have sent out email notifications instantly. My apologies to anyone who came here looking for the full story. As soon as my post went live, I saw a bone-headed mistake and took it down. Then I didn't have time to sort it out yesterday. Figures!

Thanks, CoClimber. I'll write up what I've got so far and send you a PM. I'd appreciate a second set of eyes; it might prevent further embarrassment!

[CoClimber]

I think it's great what you are doing. I believe that fuel starvation is the leading cause for engine outs and anything we can do to improve that situation is worth the time. If you want a PCB knocked out, I'd be glad to help.

[Eric Page]

My apologies to anyone who was following this little side project. I posted something about this a month ago, immediately realized I had made an error in the schematic, took it down and immediately got distracted building an airplane! The schematic error has been corrected, so I'll try again.


First, here's the interface for using the DS1603NF ultrasonic liquid sensor with an EFIS alarm input:

Schematic: [Obsolete file removed; please see post #36, below, for final version.]

Circuit board:
26580

As you can see, it's dead simple: just a couple of capacitors to clean up the supply voltage to the sensor, a 4.7kΩ pull-up resistor on the active low output, and a transistor to provide a self-test of the system.

The 4-pin connector (J1) on the end of the board mates with the one that comes installed on the sensor pigtail. This circuit will pull the EFIS alarm pin to ground when fuel is present and apply 12V when fuel is absent.

Since it takes some time for an EFIS to boot and it won't show an alarm until that's done, I incorporated a press-to-test function. This is simply a normally open pushbutton switch that, when pressed, turns off a transistor to interrupt power to the fuel sensor, causing it to restart. If you do this after the EFIS is booted up you should see the low fuel alarm while the button is pressed, and for 2.5 seconds after you release it. If the alarm then goes away, the sensor is working properly.


Next, here's the interface for use in non-EFIS equipped airplanes:

Schematic: [Obsolete file removed; please see post #36, below, for final version.]

Circuit board:
26582

This circuit flashes an indicator LED when the sensor does not detect fuel. It's a simple 555 timer based oscillator running at ~2Hz, with the output driving a 20mA LED driver IC (Microchip CL520N3-G). The LED driver may seem like overkill, but it has a few advantages:


It simplifies installation when users choose their own indicator by automatically providing 20mA to drive any LED, regardless of the compliance voltage required, up to the supply.

It protects the output of the 555 timer from overload if the installer tries to use an incandescent bulb or accidentally shorts the output to ground.

It costs $0.45.

I found an illuminated switch that I think would make a nice indicator for the sensor, and would allow the pilot to shut off the flashing to reduce distraction, or test the system by briefly interrupting power. It has a bright red LED inside, and you can install your choice of diffusers and actuator caps in various colors. The cap is meant to have a legend printed on transparency film behind it, which is visible when the LED is turned on. The face of the switch is 0.622" x 0.866" and it will mount in panels from 0.039" to 0.157" thick (my Series 5 panel is 0.070" thick). I'll order a switch, as well as diffusers and caps in white, clear and red to experiment with, to see which combination looks best. The image below shows a narrow-end view of the switch with the diffuser and cap removed.


26586

This is my quick first-pass attempt at how an indicator legend might look:

26583


I'm asking that anyone with electronics experience please take a look at the schematics and feel free to critique my work. I'm not an engineer, so I'm looking for feedback on basic function, robustness and any ideas for simplification.

You could probably reduce parts count by using a microcontroller (and likely the cost, given how cheap (https://www.digikey.com/en/products/detail/microchip-technology/ATTINY5-TSHR/2238294) they are), but I think that would represent a high barrier for builders who don't have the capability to flash firmware. You could likewise reduce board size by using surface-mount components, but again, it would be a barrier to builders who lack the equipment or skill to solder SMD.

I'll wait a few days to see if anyone has any suggestions. If there are, we can hash that out, then I'll order boards and parts. It'll take about two weeks to get everything, then I'll stuff some boards and give them a test. If they work, I'll wrap this up with instructions on where to get everything and how to assemble the boards.

[CoClimber]

Eric, sorry I dropped the ball on this. I like your idea of an illuminated switch so that you can turn off the alarm. The danger is that you leave it off but that can be a checklist item.

[Eric Page]

No worries! If you see anything that could be done better, let me know. We'll get this thing sorted out...

[Eric Page]

Circuit boards have arrived. Components should be here next Wed.

26740

[Kitfox Pilot]

Thanks Eric for your time to do all this research and development on this project. This could save a life someday.

[Eric Page]

I finally got around to populating the circuit boards and doing some tests. I'm making some small changes to the design of one of them and moving to v2.0. New boards and parts are on order.

It doesn't look like the illuminated switch that I found is going to be a good solution. It's not nearly bright enough, and the bezel isn't big enough to make a legend that says both "LOW FUEL" and "PRESS OFF" in text large enough to be readable for anyone over the age of 20. This image doesn't do a good job showing the brightness, but it's not great. It certainly wouldn't be adequate in bright sunlight; it's not very impressive in a well-lit room. I've ordered a discrete LED instead that should be much more attention-getting.

27129


Watch this space...

[n85ae]

I am replacing my header Tank, and lacking a port for the optical sensor (Thanks for that change Kitfox :) )
I am considering the non-contact liquid sensor you are using. It seems from at least a quick look at Amazon
reviews for variants of that sensor the failure rate of the sensor is about 50%, as well beneath the sticker is
supposedly a trim pot for adjusting sensitivity.

I do not have a sensor at present so I can't say if any of that is true, but you might want to look at how well
sealed, and assembled is the back side of that sensor. There seems some comments that they are sensitive
to environmental change on the backside (when for example used as outdoor Tank sensors).

Just some thoughts

Jeff

[n85ae]

I can't find the comments which I read earlier, but it seems there is concern about sensitivity
drifting, and due to the trim pot on the back, it's sensitive to environment.

27228

[Eric Page]

Can you post a link to the Amazon listing that you're looking at? I'd like to take a look at the product info and the reviews.

The image you posted above does not look like the sensor that I'm using. The DS1603NF has a gray plastic 2-piece enclosure with no flange on the edge, which is ultrasonically welded at the seam. There's a very shallow depression in the back where the sticker is located, but there's nothing underneath it.

[n85ae]

There's a bunch of essentially the same sensor on Amazon, this is the one with the image
and multiple output types, I'm looking at the high/low output sensor. Your original link is
discontinued. But I believe they are all the same, just sold by different vendors. I do a lot
of Arduino based hobby stuff, and my experience is that between Amazon, and Ebay the
same device is almost always available from a multitude of sources with different names.


Taidacent Non-Contact Liquid Level Sensor Externally Attached Liquid Induction Level Switch Water Level Switch (PNP Output(24V)): Amazon.com: Industrial & Scientific (https://www.amazon.com/dp/B07QKVJN2X/ref=sspa_dk_detail_0?spLa=ZW5jcnlwdGVkUXVhbGlmaWVy PUExNjcwSjlNMVhVTjkyJmVuY3J5cHRlZElkPUEwMjgxNDgzMk NXT0M3MEpBUk4yOCZlbmNyeXB0ZWRBZElkPUEwMTQ3NjIxMTZP RDE4WExDS0dXWSZ3aWRnZXROYW1lPXNwX2RldGFpbDImYWN0aW 9uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl&th=1)


Your idea is a good idea, but 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 ...





Jeff

[Eric Page]

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!

[n85ae]

Too late now, argument on!

Actually, not trying to be antagonistic, but Arduino is a good choice for this, here is why.

Arduino, IS a microcontroller (depending on which one, it's an ATmega variant, you can do this simple circuit
with an ATmega8 (if you want the simplest one). I have programmed the ATmega chips with AVR Studio, and have an
Chip Programmer for them. BUT it's a waste of time to do that for this. Arduino can be programmed from a PC right
off the USB port, just with a cable.

Doing these sensors doesn't actually need a microcontroller just to turn on an LED, but since they are essentially junk at
this price point/source I don't really trust them, and was just thinking of alternate ways to use them with more confidence.

if you don't worry about trying to look at the actual level, and just use the sensors as high/low detectors, it's very easy.

An Arduino to do this is $6-7 which is cheap. The circuit to do this, is just the sensors, which can be wired pretty
much directly to the Arduino, connecting power, and the output led. Then the rest is about a dozen lines of code.

I've never had an Arduino "lock up", but I have made stupid logic errors when programming them that look like that ...

Regards,
Jeff

Adafruit Trinket - Mini Microcontroller - 3.3V Logic [MicroUSB] ID: 1500 - $6.95 : Adafruit Industries, Unique & fun DIY electronics and kits (https://www.adafruit.com/product/1500?gclid=Cj0KCQiAyJOBBhDCARIsAJG2h5cZRFbHsP7HUOf lgangpuoGty_n8LnrOtJgSeFfMEAU0q9alBJ6lIoaApixEALw_ wcB)



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.

[109JB]

I agree with Eric concerning the watchdog. On an Arduino it is built in and very simple to implement. Below is how simple it is. I do think the Arduinos are pretty robust. I've got them running my CNC milling machine conversion, my 3d printer, and other stuff too. They have never failed me even running for days, or in the case of my sump pit water detector (Arduino Nano based), it has been running for about 6 years now.


Minimum code for watchdog:

#include <arv/wdt.h> //the library for the watchdog timer


void setup(){
wdt_enable(WDTO_4S); //enable watchdog timer with 4 second timeout
}


void loop(){
//Your main code here to do whatever


wdt_reset(); //resets the watchdog timer each time through the main program loop
}

[CoClimber]

Wow. In all my years working with Arduinos, I never noticed that they have a watchdog function. I have a Teensy 4 based EMS in my panel and will implement that the next time I am in the code.

[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 (https://www.amazon.com/s?k=DS1603NF), eBay (https://www.ebay.com/sch/i.html?_nkw=DS1603NF+Ultrasonic) or AliExpress (https://www.aliexpress.com/wholesale?SearchText=DS1603NF+Ultrasonic) (search links). See the first post in this thread, above, where I discuss sensor position on the header tank.

For EFIS-Equipped Aircraft

27518

Schematic/Wiring Diagram: 27521
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

27519

Schematic/Wiring Diagram: 27522
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.

27520

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 (https://teamkitfox.com/Forums/private.php?do=newpm&u=8892) 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 (https://teamkitfox.com/Forums/threads/11143-New-Low-Fuel-Alarm-Sensor?p=98154&viewfull=1#post98154), to purchase blank circuit boards and components to assemble either type of interface.

[napierm]

Any of these installed in a flying airplane? PIREP?