to control ground resistance for a vehicle fuel gauge

Hi, on my car project, i would like to use fuel gauge for dual reading: with a toggle switch i could select the gauge to 1) reveice input from tank sender, as originally 2) receive signal from arduino (to show a measurement of an engine parameter).

The tank sender is most propably 0-100ohm.

How can i make Arduino to mimic the same resistance scale on it's output?

Thanks :)

Without doing a lot of research the only way I can think of is a servo or small stepper coupled to the shaft of a 100 ohm pot.

Thanks for your pro response, that helps me not to waste time to find a sophisticated solution. I'll consider, for the gauge second reading, to give it solid ground and control gauge VDC with arduino PWM. Thanks again.

Don’t see that it’s too hard…

drive the digital output with a PWM signal, and should be fine

outline circuit appended…

note I’ve presumed that the sensor has one side connected to +ve and one side of the meter is grounded … vehicles I’ve worked on have it that way round.

if this is wrong, post again and I’ll re-arrange the circuit.



meter co.pdf (20.6 KB)

I think you have drawn the p-channel fet upside down. Source goes to +12volt. Common bug of drawing programs to present a p-channel fet source down. Gets me every time too.

Instrument is most likely connected to 12volt, and tank sender connected to ground. That makes the circuit easier, with just an n-channel fet. I leave it over to you to draw it. Leo..

sorry Leo - as you say, we often just rush away with the basic idea and get something wrong… ho hum.

To complete the job I append an ammended original circuit, and the alternative with
grounded tank sensor.



meter co1.pdf (20.6 KB)

meter co2.pdf (19.2 KB)

Be aware that some cars (not sure just which ones) have some sort of funky "regulator" circuit as part of the fuel (and other) gauges circuit (part of the instrument panel wiring). The ones I have seen have some sort of "pulsing" at a low frequency (1 hz or near there) to average the power out. Trying to generate a pseudo-resistor working against something like that can be tricky (my older Toyota truck has that sort of thing). The tank sensor is just a variable resistor (1-130 ohm) with one side grounded and the other side going to the meter, but trying to put a solid state sender in worked for a while but has caused interesting issues because of that regulator.


Modern cars!!! Grrr !

I've come across some which test a bulb at turn-on, then if it's open circuit , don't send power to it. So when you test for volts with that light turned on, you see 0v and start tearing the wiring loom apart. I think that was a FIAT.

back to the meter....... if it's done like that all bets are off.

But the OP may be lucky and have a conventional system.... give it a try