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-   -   Cost effective binary fuel pressure sensor? (https://vansairforce.net/community/showthread.php?t=145475)

maniago 01-05-2017 08:14 PM

Cost effective binary fuel pressure sensor?
 
I have two 5gal aux tanks that will pump into my main wet wings. Been running all over the internet looking for a low pressure fuel switch that I can T into the feed line to tell me when the line pump runs the aux tank dry. Just some simple "there is pressure/there isnt pressure" switch that I can hook an idiot light to, to tell me to shut the pump off. Not at all keen on a diaphram/contactor style sensor as is typical for oil pressure switches. Just seems like an explosion waiting to happen when used with fuel/fuel vapor.

I also looked at optical sensors, but they are some $200+ per, and the economical plastic Honeywell ones are metric threads so no joy on a T (though I could hog one out of brass if I have to).

Anyone got any ideas?

greghughespdx 01-05-2017 08:20 PM

Like this? 80 PSI, 1/8?-27 NPT THREAD

maniago 01-05-2017 08:27 PM

Thats a piezo electric transducer, I'm pretty sure. It'll put out a varied voltage for a given pressure. I have no idea how to make that be a binary on/off 12v signal. I'm not a circuit guy or for sure I'd do it.

RVDan 01-05-2017 09:02 PM

Diaphragm type switches are reliability used in aerospace applications. Stewart Warner/hobbs switches are used in many GA airplanes for fuel and oil pressure. Might give them a try.

maniago 01-05-2017 09:17 PM

Like the Honeywell contactor units, the Stewart Warner 5000 series only list oils and Jet fuels, not gasoline or combustible fuels. Maybe I'm being overly cautious, but I dont get a warm fuzzy about using them in a 100LL line.

rv7charlie 01-05-2017 09:35 PM

That's a knockoff of the Kavlico; available in many different pressure ranges. Zero to ~4.5volts output at full scale. Google 'voltage comparator' to find a circuit that you can set to trip at the voltage of your choice.

Or, find an oil pressure sender for a car that uses an 'idiot light' instead of a gauge. But you'll need to run your transfer line at similar pressures to an oil pump on an engine.

Optical sensors aren't always $200.
http://www.ebay.com/itm/GEMS-ELS-950...AAAOSwh2xYB90M

But...I contemplated doing it that way. If you insert it in a T fitting, the sensor T will probably need to be just above horizontal, so the fuel can cover the sensor cone while flowing, and drain away from it when the line empties.

Charlie

Canadian_JOY 01-05-2017 10:08 PM

Check out Pillar Point... Their optical sensors work pretty well.
http://www.pillarpointelectronics.com/sensors.html

maniago 01-06-2017 05:46 AM

Quote:

Originally Posted by Canadian_JOY (Post 1139595)
Check out Pillar Point... Their optical sensors work pretty well.
http://www.pillarpointelectronics.com/sensors.html

Ah, now were talking. Thanks for this. These guys are using the metal GEMS sensor that I see thats well over $200 on Mouser, but in a package deal, esp the T arrangement. Might just do the trick.

-------
Looks like these guys had at one time (2003) a controller for the Facet cube pump to do exactly what I'm talking about, but Facet changed the pump design, so Pillar went with a more generic "controller" ala their existing off board set up.........

Thanks again to DR and VAF for a great info resource.

avionicsr 01-06-2017 06:47 AM

Quote:

Originally Posted by maniago (Post 1139557)
I have two 5gal aux tanks that will pump into my main wet wings. Been running all over the internet looking for a low pressure fuel switch that I can T into the feed line to tell me when the line pump runs the aux tank dry. Just some simple "there is pressure/there isnt pressure" switch that I can hook an idiot light to, to tell me to shut the pump off. Not at all keen on a diaphram/contactor style sensor as is typical for oil pressure switches. Just seems like an explosion waiting to happen when used with fuel/fuel vapor.

I also looked at optical sensors, but they are some $200+ per, and the economical plastic Honeywell ones are metric threads so no joy on a T (though I could hog one out of brass if I have to).

Anyone got any ideas?

You may find something here that will work:

http://www.omega.com/subsection/opti...FdgKgQodiQ4BoA

JurcaSperocco 01-06-2017 07:03 AM

Hi,

I'm using the optical sensors from Aircraft Extra, $51 cont. USA.

http://www.aircraftextras.com/FuelSensor1.htm

They are 12 mm diameter, sorry metric thread 100.

Doc here: http://www.aircraftextras.com/Manual...Spec%20Sht.pdf

I plan to mount on the fuel line.

Hope this helps,

WingsOnWheels 01-09-2017 07:12 AM

Is there a particular pressure you are looking at for the light to come on? If not, what about one of the oil pressure switches like used for the HOBBS, I think those are set to around 5psi.


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