[DeTomaso] Fuel Gage Linearizer
Edward A. Nauman
enauman at roadrunner.com
Sun Nov 2 09:05:08 EST 2008
Thanks for the info. I don't want to give the impression that I'm trying to
market the device. I just wanted to make it available to the guys if they
were interested. Regarding Thomas' device, it sounds like the same
principal only the EEPROM is built into the microcontroller in my case. The
box I built will work with any combination of sender/gage in the automotive
industry. It wouldn't take very much additional programming to make user
calibration possible. It has an RS232 port built in and the PIC is an "in
circuit" programmable device. Like everything I design for myself, it's
over engineered so it would be expensive to market it with the intent of
making money. Besides I like production manufacturing about as much as I
like root canals... :) Here is a link to another design that I did for fun
that would never make it to the merchandise shelves.
http://www.youtube.com/watch?v=xtlN_9sXn3c
Cheers
Fast Eddie
Edward A. Nauman\
C.E.O.
Smart Litez Inc
Palmdale, CA. 93551
(661) 305-7636
> -----Original Message-----
> From: John Taphorn [mailto:jtaphorn at kingwoodcable.com]
> Sent: Sunday, November 02, 2008 5:43 AM
> To: Edward A. Nauman; Email Forum Pantera
> Subject: Re: [DeTomaso] Fuel Gage Linearizer
>
> Ed
>
> Several years back, Thomas Tornblom offered his electrical engineering
> expertise to the group with an alternative solution he called his Gauge
> Corrector.
>
> It is an adjustable eeprom to match the sender to any gauge. If I
> recall
> correctly, the eeprom can store 10 data points. Thus, I was able to
> adjust
> my fuel gauge to read accurately at 1/8th intervals by filling the tank
> 2.65
> gals at a time and storing the value. Of course, it assumes that the
> quantity of fuel used between those data points is linear for a given
> drop
> in the float arm. However, accuracy at 1/8th intervals is close enough
> for
> me. Obviously, if you are using a data point for every gallon verses
> 2.65
> gals, your approach will be more accurate between my 1/8th data points.
>
> Although a benefit of Tom's eeprom approach is that I was able to
> calibrate
> it myself and could easily perform the operation again should I change
> my
> gauges to a set with a different impedance. I.E. I am currently using
> it on
> my Auto Meter, but could have used it on my Veglia initially.
>
> I don't know if Thomas is still offering the product. It was very
> inexpensive and has the JT Seal of Approval.
>
> I am not trying to discourage your idea or willingness to help, simply
> illuminating the possibilities and the contributions of others.
>
> JT
>
>
> ----- Original Message -----
> From: "Edward A. Nauman" <enauman at roadrunner.com>
> To: "Email Forum Pantera" <detomaso at realbig.com>
> Sent: Saturday, November 01, 2008 1:56 PM
> Subject: [DeTomaso] Fuel Gage Linearizer
>
>
> > 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
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >>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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