0-90ohm fuel sender to xf (volatge) gauge PROJECT

[judgetread 757]

So firstly I'm no electrical engineer or whatever, so if anyone see's any obvious issues, problem or possible explosive results please let me know

 

OK, so I didn't really look around so I have no idea if there is ant commercial  product out there that would suit this project already, but hey electronics had been a hobby for a fair while when I was young so I thought I have a crack at this myself, keep myself active and out of trouble. So yes it could be a waste of time if something already exists but I find it interesting to play and learn (and fail often)

 

I'm planning on adding a fuel cell to my xf ghia, getting rid of the standard tank and replacing it with a 60 or so litre fuel cell so it will suit my future plans.

 

Problem is, most aftermarket fuel cells come with either a 0-90ohm or 7-97ohm resistance fuel sender. The problem is this will not work for the xf fuel gauge as it uses a volt system 0.2 to 4.2 volts to display the fuel level. So the project begins, make a conversion from the resistance type fuel senders for a voltage based display gauge

 

 

The goals are:

* Gauge requires input of Volts: [ empty = 0.2 volts, full = 4.2 volts ]
* The sender, sends in ohms. [ empty = 0 ohms, full = 90 ohms ]

* Any power must be from the 12 volt DC system the car current uses, no external power or crap.

 

I drew up a schematic using a op-amp/comparator setup and a voltage divider. Added in a 5 volt regulator to the schematic from 12 volt to supply the currect volt and current needed for op-amp and resistor ratings.

I also adding in a variable trim pot, so within the same ratio other senders should work as well, such as 7-97ohm sender.

 

Using altium designer, converted the schematic to a pcb layout, adding in silk screens, overlays etc. Taking into account I didnt have any stuff available to make my own pcbs, the costs to buy all the stuff was not viable and I was planning on using SMD's, I designed to have them made.

 

[judgetread 757]

After designing the boards, I searched around and found a absolute great deal to have to pcb's made for me, I sent the Gerber files ( files the pcb board making place needs) to a board manufacturer and for a massive $9.90usd including postage have 10 pcb's boards made to the designs.

The only down side with getting these made so cheap, was the wait time. From sending the gerber's in to receiving the boards was just on 4 weeks wait but for $9.90 I cant complain. The boards come etched, silk screened, padded, and solder masked, really trying to do this myself would of been just a nightmare, the boards only meassure 5cm x 2.7cm to start with , then trying to etched the smd pads on the op amp would never of happened, so Im a happy chap.

 

 

Now, I admit my first time using SMD's components and well it wasn't that much fun soldering them to the board, using 0805's was bad enough soldering, the stupid op-amp pin pitch was crazy to solder, but in the end I got through it

Sorry about the bad pictures, camera on phone has crapped it and well these components are so friggin small.

 

 

With the board together time for a test.

Hooked it up to a DMM and a bread board and after playing around with the trim pot to fine tune out any tolerance in components all seems pretty good.

 

Hooked up with 3 ohms resistance, give out a 0.2 volts result

 

 

Hooked up to 90 ohms resistance puts out 4.21 volts

 

By adjusting the trim pot, was able to get 7-97 ohms resistors working as well, so a sender with 7-97ohm should work too.

[judgetread 757]

So, finally got around to making a case for it all, and a few pictures.

 

Adding some standoffs for the pcb to sit on

 

pcb clipped in, I also made another board this time soldering the wires directly to the board. Easier, cheaper and less stuff to go wrong.

 

A hole on the bottom of the case, where you can adjust the trimpot. Remebering its a 90ohms difference you can set the range with it so like 0-90 or 7-97 or 8-98 etc.

 

Finished box

 

Just as a size comparison to a standard 9volt battery.

 

Overall, everything worked out pretty well, except I doubt id do a SMD component project again. Well maybe for the resistors and caps, but not the IC, they are just way to small and a pain to do.

 

I have everything to set it up done now, I just need to install the fuel cell and hook it up but that may be awhile or may not

 

 

Edit: I just did a quick sticker to wrap around it. well cause I was bored

[gerg 10,871]

Awesome. You might find a few folks on here who would be interested in this conversion, if only for the fact that stock senders don't like modern fuels.

[judgetread 757]

Im going out to the shed today to try it out on the xf, so we'll see if it works or not I might have to make adjustments to compensate for wiring resistance and voltage drop to the gauge, but ill find out very soon

 

Awesome. You might find a few folks on here who would be interested in this conversion, if only for the fact that stock senders don't like modern fuels.

I guess it would work for any sender that uses a resistances based system, even lpg? I never had any commercial plans, but if people are interested I could put into a case and post.

 

Without working it out I guess it uses about 4-5$ in parts to make + the $1 board maybe less

[Outback Jack 6,352]

Bloody nice work Judgetread

I would be whacking a patent on that shit quick smart, or at least a copy right .

I always hated soldering SMD's even with paste they are a pain in the arse.

Looking forward to your results, but from ya schematic and tests, looks to be a goer.

 

Best of Luck.

 

Jack.

[judgetread 757]

I always hated soldering SMD's even with paste they are a pain in the arse.

 

Haa yeh, my first time working with em, normally use the old through hole. Was interesting using a jewelers loop just to see the solder joins and how they sat

[VDO 124]

Wouldn't it be a lot simpler to replace the magnetic gauge movement in the XF with a 0-90 ohms magnetic movement as used in early Corvette, Camaro, Pontiac Firebird, and Humber Super Snipe..?

[judgetread 757]

maybe but its a digital dash

 

I guess ill see soon enough, its i can make it a simple plug and play setup, either way I just want to play around and have original fuel gauge working

[VDO 124]

Oops... didn't know it was the digital dash.

[deankxf 20,266]

Oops... didn't know it was the digital dash.

wouldnt make any difference, the guages work when you fit a digital dash to the GL

[deankxf 20,266]

gas guages interfaces used to be available to do this conversion.

[judgetread 757]

well had some issues, couldnt get enough current through to the gauge when hooked up, or so I thought ...

 

The 1k resistor was to high compared to the cars resistance, so bridging them pads on R2 and all seems to be working atm. But dark now to do a final test but was able get full and half tank to show at the correct ohms resistance.

With many thanks to someone else for the help working that out.

 

 

Ill get it all together and pics, then maybe a new electronics project?? 8 - 6 tacho convertor, and i know there are commercially available.

[judgetread 757]

Ok, finally got time to do some more on this.

 

Hooked it up to a fuel cell, and it is working well. Seems the xf digital dash lags by about 5-7 seconds, so i guess the dash gauge updates itself every 5-10 seconds, which seems normal and fine.

 

Trying to get all the stuff packed into a project box all neat and secure today, but between the nrl, cricket and v8's its hard to find the time to get it all done

[gerg 10,871]

The "lag" is deliberately built into the electronics of the gauge to eliminate the effect of the level rising and falling with the fuel sloshing around. You notice this also just after filling up and the gauge takes half a minute or so to get up to the full mark.

[judgetread 757]

The "lag" is deliberately built into the electronics of the gauge to eliminate the effect of the level rising and falling with the fuel sloshing around. You notice this also just after filling up and the gauge takes half a minute or so to get up to the full mark.

Yeh I figure it was like that

 

Updated first posts with completed project

[Lord_fahrquhar 2,580]

Got a business name for it.

 

The unfuckit

 

Your ford got a fucked fuel gauge? Yeah you and every other non ls owning xd-xf operator. Unfuckit will use any standard 90 ohm unit like the rest of the unverse to give you accurate fuel gauge readings.

[Lord_fahrquhar 2,580]

Testimonials:

 

Unfuckit stopped that whinging Scotsman that he canna get more power. Unfuckit gave us great readings on the level of he dilithium crystals so much so I don't understand why on a fucking starship they used an antique capacitance based fuel gauge

[XFG Panno 0]

Threadmining I know, but it is the best hit google gave me:

Judgetread - Are these commercially available yet?

 

Im doing a Barra conversion in my XF Panno. I have just installed a XH fuel tank but need to adapt the resistive fuel sender to work with the XF dash?

[Crazy2287 1,886]

Im also interested to see what the final design was to get a resistor sender to talk to the factory capacitive signal input.

[judgetread 757]

Ive one got one made sorry . I have pcb's and most pars if your handy with a soldering iron to put one together ...

[Crazy2287 1,886]

Not too worried about that, Could verobord one. Just interested in the schematic and theory of operation for the final design. Did it work and allow you full sweep of the instrument cluster? stuff like that.

[nickyp00 13]

Hi,

new here guys but this would be verry handy for my project. I have an xd falcon utility and have instaled a 5l v8 out of a eb falcon including the 4 speed btr automatic. To save clutter, mucking around and complication I have installed a fuel tank with built in pump out of a 98 xh falcon utility and of course I have the same probem as everybody else with converting the system to accept a resistance type sender unit. My sender unit measures outside the range specified in the above schematic being 2.2 ohms empty to 180 ohms full. I guess I could change the trim pot value to increase the operating range. How does the 7805 regulator go dropping the 12 - 14v down the 5v heat wize, its a fairly big drop. I had a thought to build a simple voltage divider using a 5v reg and the sender unit personally. Interesting use of the ic in the circuit. Have enjoyed electronics as a hobby for a long time but did not delve into the ic side of things that much. Not trying to steal the thunder from the previous bloes design cause it seems verry plausible solution, I have come up with my own design.  

Edited May 27, 2017 by nickyp00
Circuit I designed

[Stu5766 394]

I had a similar issue when I fitted the mustang tank to the XD.

I used a peel unit interface to convert from ohms to capacitance.

i have a couple of 0-90 units here if anyone is interested.

cheets stu.

[dex 2,065]

Neat lookn ute regardless