[DeTomaso] Fuel Gage Linearizer
Asa Jay Laughton
asajay at asajay.com
Sat Nov 1 21:22:22 EDT 2008
Eddie,
Beautiful dissertation. Part of me is a geek and wants a kit. Part of
me simply fills the tank when it gets below a half or a quarter. Part
of me knows that if I miss those two opportunities, the little red light
reminds me I better fill up at the very next station I pass. I
understand how each sending unit/gauge combination will be different and
I think you came up with a brilliant solution, I just don't know if
there is that much of a market for it.
I love the idea though,
Asa Jay
Asa Jay Laughton, MSgt, USAFR, Retired
& Shelley Marie
Spokane, WA
1971 Mach I Mustang [ASA JAY]
1973 Pantera L 5533 [ASASCAT]
******************************
http://www.asajay.com
http://www.351c.info
Edward A. Nauman wrote:
> Hi guys,
>
> I have been away from the list for a while and was searching through
> the archives. I came across a message about a circuit I designed a couple
> of years ago. Being an instrumentation engineer for 3 decades, one of my
> pet peeves developed over the years is the non-linearity of automotive fuel
> gages. The fuel gage in most cars is really a fuel level gage and not a
> fuel quantity gage. Since the fuel level transducer is usually a wire-wound
> potentiometer actuated by a float at the end of an arm, the potentiometer
> output is proportional to the angle of the float arm which is a sinusoidal
> function. Most of the automotive fuel level pots I have examined have a
> linear output with respect to rotation angle of the shaft. So, the fuel
> level with respect to the output of the potentiometer becomes a function of
> the length of the float arm and the sin of it's angle. In other words the
> measurement, if uncorrected, is non-linear. This is sometimes corrected for
> by manufacturing a non-linear pot that linearizes the sinusoidal output in
> the range of interest. Remember, that is for fuel LEVEL. When you
> translate level into quantity. The shape of the fuel tank becomes the next
> source of non-linearity. Obviously if you had a cone shaped tank, one inch
> of fuel level near the top is a lot more than quantity 1 inch at the bottom.
> Depending on the irregularity of the cross-sectional area of the tank as the
> fuel level rises, the equation for quantity Vs. level can get quite
> complicated. The simplest way to correct the situation and still be
> adaptable to different tank shapes and sizes is to use a micro-controller
> and a calibrated look up table to translate the level into actual quantity.
> The design I came up with for my car uses a PIC microcontroller that has on
> board an EEPROM to store the look-up table. Operationally, the fuel level
> potentiometer is connected to my circuit which reads the resistance and
> "looks up" the correct corresponding fuel quantity. It then drives the gage
> with the correct voltage to indicate the actual quantity. The setup
> requires calibrating the tank at 1 gallon intervals which means draining the
> tank and filling it one gallon at a time. Since I was only building one of
> these circuits for myself, I did not write any code to have the micro
> perform the calibration automatically, meaning, that I recorded ADC output
> on my computer, generated the lookup table with Excel and manually entered
> the lookup table into the micro. I did the same thing for the one I built
> for Chuck Buthala. But that meant he had to perform the calibration, email
> me the data, and I programmed his look up table and sent the box to him.
>
> If you guys are interested in something like this, I can do 1 of 2
> things. I can put together a kit consisting of a PCB and a parts list with
> a schematic and a wiring diagram. Or, I can build you one and send it to
> you with installation instructions. But unless you are familiar with PIC
> microcontrollers and own a programmer, you would have to send me the data
> and I would have to program it and send it back to you. In order for me to
> write the code for an auto calibration routine, I would have to have enough
> commitments to justify the time spent. Bear in mind, I'm not trying to make
> money here, just offering this to my Pantera brothers if they are
> interested. If there is enough interest, I will figure out a price based on
> the responses I get.
>
>
> Cheers,
>
> Fast Eddie (#2100)
>
>
> P.S. If my explanation is either too complicated or too simple, please let
> me know and I will clarify any questions you may have.
>
>
>
>
>
> Edward A. Nauman\
>
> C.E.O.
>
> Smart Litez Inc
>
>
>
> Palmdale, CA. 93551
>
> (661) 305-7636
>
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>> The circuit was designed by Ed Nauman. He built one for me and it works
>>
> great. The gizmo works with a chip which uses the sending unit resistance,
> compares it to a look up table in the memory and >sends the correct signal
> to the gage. You have to go though a calibration cycle to set it up. There
> is an article in the POCA news about two years ago on the circuit. Ed if
> your listening I hope my >description is correct.
>
>
>> "www.ProvaMo.com" <pantera007 at sbcglobal.net
>>
> <http://list.realbig.com/mailman/listinfo/detomaso> > wrote: It was not
> "Me" Chuck that Ohm'ed, but I did test one gallon at a time, the
>
>> ohming was, I think, someone in the Nordic region perhaps.
>>
>
>
>> Chuck
>>
>
>
> -----Original Message-----
> From: detomaso-bounces at realbig.com
> <http://list.realbig.com/mailman/listinfo/detomaso>
> [mailto:detomaso-bounces at realbig.com
> <http://list.realbig.com/mailman/listinfo/detomaso> ]On
> Behalf Of Mark McWhinney
> Sent: Tuesday, July 24, 2007 10:41 AM
> To: 'Garth Rodericks'; detomaso at realbig.com
> <http://list.realbig.com/mailman/listinfo/detomaso>
> Subject: Re: [DeTomaso] Incorrect gas gauge
>
>
> Some of the fancier aftermarket gauges allow for multiple calibration
> points. I think little Larry has that. If he is lurking, may he can fill
> us in.
>
> As I recall, Chuck did the one-gallon at a time work to record the ohm
> readings.
>
>
> -----Original Message-----
> From: detomaso-bounces at realbig.com
> <http://list.realbig.com/mailman/listinfo/detomaso>
> [mailto:detomaso-bounces at realbig.com
> <http://list.realbig.com/mailman/listinfo/detomaso> ] On
> Behalf Of Garth Rodericks
> Sent: Tuesday, July 24, 2007 10:33 AM
> To: detomaso at realbig.com
> <http://list.realbig.com/mailman/listinfo/detomaso>
> Subject: [DeTomaso] Incorrect gas gauge
>
> Just another reference point for the non-calibrated nature of our gas
> gauges.
>
> When mine is full it registers Full.
> 40 miles after fill up it registers at the 3/4 mark, or slightly below.
> But I can drive for quite a long time between 1/2 tank and Empty.
> And, at Empty the warning light comes on.
>
> I have not tested how far I can go after the warning light comes on,
> however the most I've
> been able to add at a fill up was 19.5 gallons.
>
> Now, I recall a year or two back that someone posted that they made a
> simple electronic
> converter to calibrate the fuel gauge. I think they took ohm readings from
> the sender as they
> filled the tank 1 gallon at a time, then created a mapping table to send
> an accurate reading
> to the gauge. Does anyone remember who that was? I recall they were
> planning to make it
> available for sale, but I never saw anything more on it. Does anyone have
> more info? I'd like
> one.
>
> Cheers!
> Garth
> #4033
>
> YMMV,
> Garth
> #4033
>
>
> ---------------------------------
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