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| Anyone familiar with vehicle fuel gauges? |
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| MrOmnos:
Hi, I am trying to make something that can connect to existing fuel gauges in vehicles and display the amount of fuel in percentage. I am guessing all types of fuel gauges used today probably have analogue voltage on the wires coming out of the tank. Is this correct assumption? Anyone here have any knowledge on fuel gauges that would like to share? It would be really help if you could share anything you know about fuel gauges. Meanwhile I am also google. Thank you! |
| vk6zgo:
--- Quote from: MrOmnos on March 24, 2020, 12:47:54 pm ---Hi, I am trying to make something that can connect to existing fuel gauges in vehicles and display the amount of fuel in percentage. I am guessing all types of fuel gauges used today probably have analogue voltage on the wires coming out of the tank. Is this correct assumption? Anyone here have any knowledge on fuel gauges that would like to share? It would be really help if you could share anything you know about fuel gauges. Meanwhile I am also google. Thank you! --- End quote --- I haven't had anything to do with fuel gauges for a long time, but in the time I did play with them, there were two types:- The really old ones used a resistive sensor in the tank & (I think--it's ages ago) a twin coil meter movement in the dash---It certainly wasn't a permanent magnet, moving coil! These would come up almost instantly to the correct reading when the ignition was turned on. Old tanks had baffles in them so the fuel wouldn't slosh round when driving,(cornering, etc), allowing the reading to remain pretty steady. The "bean counters" saw these baffles as a waste of money, & decreed that they be no more. All good, but now the reading jumped all over the place, which is why the baffles were there in the first place. :palm: The answer to this was to make the meter slow to respond. To this end, they used thermal meters-- they apparently used some sort of bi-metal spring. This worked well, except that it was a bit unnerving to fill your near empty tank up, & wait about a km for the reading to go to "full". My car didn't have a low fuel light, so I played around, trying to design one. I ended up with a rough "first draft" which worked, but real life intervened, & it got shelved, never to be seen again.p :( I would expect modern temperature gauges to do this "damping" function electronically, either analog or digitally. Many fuel gauges rhese days are "rendered" on the dash display, not real electromechanical ones. |
| schmitt trigger:
I remember the thermal meters. They required 10s of milliamps at full scale. As you mention, nowadays everything in vehicles has become electronic and most recently bussed. I haven't poked around in a modern auto, but I suspect that nowadays fuel level data may be transmitted via LIN or CANBUS. |
| PKTKS:
Floating resistor gauge wired to OBDII likely may be encapsulated on CAN or other proprietary protocol as well Paul |
| unknownparticle:
Dunno about your issue but I have to fix a problem with reserve fuel indication on my 15 year old MV Agusta motorcycle. Bikes used to have, many years ago, a reserve fuel tap. So, you rode on main tap until the engine started to miss or even stopped, then turned on the reserve tap, whilst still moving, by hand after groping around under the fuel thank! All very ancient tech and clumsy, but you knew where you were! Now, with my MV, there SHOULD be a reserve level indicator light on the dash so you know you have about 20 miles to find fuel. Except, mine stopped working, with obvious consequences. So, I browsed the manual to find out how it worked and it's basically a thermistor capsule on a stick that becomes exposed when the fuel level drops, thus an increase in temp, thus a signal to the dash module, light comes on. So the thermistor is dead, MV can no longer supply the part, so I have to find an alternative. Great! Although, if that part had been available, it would have cost about £150.00!!! |
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