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Cost effective binary fuel pressure sensor?

maniago

maniago

Well Known Member
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?
 
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.
 
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.
 
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.
 
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-Rugged-Series-Electro-Optic-Level-Sensor-12VDC-224506-Fluid-12V-/191634359642?hash=item2c9e4c455a:g:G~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 said:
Check out Pillar Point... Their optical sensors work pretty well.
http://www.pillarpointelectronics.com/sensors.html
Click to expand...

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.
 
Last edited:
maniago said:
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?
Click to expand...

You may find something here that will work:

http://www.omega.com/subsection/opt...witches.html?gclid=CJfEh9DTrdECFdgKgQodiQ4BoA
 
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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