Capacitive fuel Gauges

E

eddu107

Filing Flight Plan
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eddu107
Hello?
Am not sure as to whether I should address Mr Jim Weir directly or even if this is the correct forum or if anyone else can help me with this. I am an Electrical and Electronics Engineering Student in Kenya. I am doing a project on automated refueling systems especially for diesel generators while also remotely monitoring the fuel levels. It is basically an embedded system with a microcontroller and ideally would use level sensors. However am having problems acquiring such sensors due to cost and time constraints and while researching on how to build homemade level sensors i came across some articles Mr Weir had written back in the year 2000 on capacitive fuel gauges.The articles are available on this link, www.rst-engr.com/kitplanes/ under the title, capacitive fuel gauges. My question is, is it possible to use such a fuel gauge in place of level sensors and in place of the 0-5V gauge the output is instead fed to an Atmega32 Microcontroller whose maximum operating voltage is 6.0 Volts and maximum current for any of the pins is 20mA.

I was supposed to post the question in this section for Mr Weir and i dont know if I have done it correctly but any assistance would be greatly appreciated.
Thanks.
Edwin.
 
eddu107 said:
Hello?
Am not sure as to whether I should address Mr Jim Weir directly
I was supposed to post the question in this section for Mr Weir and i dont know if I have done it correctly but any assistance would be greatly appreciated.
Thanks.
Edwin.
Click to expand...

Folks, this is a little OT, but my normal place for answering this sort of stuff is blocked from Kenya, so if you can bear with me ...

Thanks,

Jim
 
Last edited:
OK, here we go ...

If you have two metal plates separated by a dielectric, you have a capacitor. In particular, if you have two metal plates, each of them one foot square and separated by a plastic washer 0.010" thick with air in between you have a capacitor of approximately 3.2 nanofarads.

If you allow jet fuel or diesel or kerosene to fill that gap between the plates you now have a capacitor with approximately double the capacitance, or about 6.5 nanofarads. If it only fills it half way, then you are halfway between 3.2 and 6.5 or 4.8 nanofarads. It is linear with fill factor.

That's the extent of the design. You are an electronic engineering student. You need to find out how to change a variable capacitance into the parameters that your circuit needs to work, and that will be like your job when you graduate with your engineering degree. Best you find out in school how that all works before you get into the profession.

I will, however, give you a pointer. Allow that capacitor to be the C in an RC oscillator. THen figure out how to change frequency of the oscillator to voltage to run your microprocessor.

Best of luck,

Jim
 
Thanks Jim, I can work on it from there. Nice articles by the way!
 
weirdjim said:
Do ya, do ya mean that after twenty years of monthly articles I'm an overnight success?

:rofl:

Thanks,

Jim
Click to expand...
Isn't that like saying that someone saved a hundred thousand dollars a year but even after 10 yrs, 11 months and 29 days they still didn't have a million.

But on the beginning of the 11th year, they crossed that million dollar mark.
Are they an overnight millionaire?
 
weirdjim said:
Do ya, do ya mean that after twenty years of monthly articles I'm an overnight success?

:rofl:

Thanks,

Jim
Click to expand...
I'm sorry, but I finally noticed the name on those articles:redface:

...after only 6 or 8 months.
 
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