nickyp00

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.  

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.