revenger 472 Posted September 14, 2016 A friend of mine is an old car collector, One of his old Packard's has a condition common to many old cars with the fuel gauge indicator. the float in the tank moves a lot due to the old style tanks I suppose. it causes the indicator on the dash to sway up and down as well while making turns and such. We were wondering if there is a circuit that can be added across the gauge to dampen the voltage fluctuations so it reads steady yet still gives a accurate level of fuel on the indicator. I was thinking about something with a capacitor and resistor with a time constant that discharges the cap slow enough to keep the gauge at a steady level yet quick enough indicate the fuel level going down. It is a 12 volt positive ground system. Thanks Quote Share this post Link to post Share on other sites
dino71 7 Posted September 14, 2016 I am no car expert but I do own an MGB so I feel for this mans electrical woes. I read about some people having the same problem with English cars and the fix was to add a resistor somewhere before the wire that goes to the gauge. I think the resistor slows down the signal so that the needle doesn't jump around like a Pogo stick. Perhaps an electrical engineer will chime in and comment. 1 Quote Share this post Link to post Share on other sites
Malsua 1,422 Posted September 14, 2016 You could start with a 1 micro farad between the terminal on the gauge to ground. That should delay the voltage drop. Up the cap size until you get the desired result. Option 2, get a Raspberry Pi variable voltage divider with a couple optos, measure the output from the tank and average the values over 10 or 20 seconds and supply it to the gauge with a regulator. It'd be as rock steady as a modern vehicle. You'd have to transform down the car 12v to 5v for the board, but other than that, it's a very doable solution as well. There also may even be a way to adapt something from a more modern vehicle (say 70s-80s) and just insert it in the circuit. Quote Share this post Link to post Share on other sites
AverageJoe 95 Posted September 14, 2016 Can also look into Anti Slosh Foam kits for fuel tanks. http://www.ksrfoam.com/Gas_tank_foam_.php and its MIL SPEC! lol Quote Share this post Link to post Share on other sites
Displaced Texan 11,647 Posted September 14, 2016 You could start with a 1 micro farad between the terminal on the gauge to ground. That should delay the voltage drop. Up the cap size until you get the desired result. Option 2, get a Raspberry Pi variable voltage divider with a couple optos, measure the output from the tank and average the values over 10 or 20 seconds and supply it to the gauge with a regulator. It'd be as rock steady as a modern vehicle. You'd have to transform down the car 12v to 5v for the board, but other than that, it's a very doable solution as well. There also may even be a way to adapt something from a more modern vehicle (say 70s-80s) and just insert it in the circuit. Malsua has it right with option 1. Cost of about a buck, and a few minutes labor. Quote Share this post Link to post Share on other sites
mipafox 438 Posted September 14, 2016 Reset trip odometer every time he gasses up. He should know how many miles he gets from a tank within a margin of error. Quote Share this post Link to post Share on other sites