How to drive a fuel gauge from an information cluster.

Projects General Guidance
1

I gutted an information cluster from an old Audi 80 b4. The information cluster, from what i know, uses resistance to determine what value to show on the gauge. I presume that means i just need to limit the current flowing to the gauge. Is it possible to do that with an Arduino? I thought about using PWM to somehow limit the current, but I don't think that's how it works. If it matters, the current draw at a full short to ground is 200mA, so I'm going to be using a MOSFET to drive the gauge

2

Try and get a glance into the wiring diagram of the car and what kind of sensor it uses. In the old days the fuel sensor was a float turning a simpel potentiometer. In that case the indicator was a pure voltmeter.
Now days? Maybe different.

3

I would expect PWM to work. It's what I would try based on what you have said.

4

I have driven this type of display with PWM, used it as a clock display.

5

There are 3 types of "analog"(have a needle) gauges that I know of.

  1. Mechanical - No electrical parts so are of no use here.

  2. Electrical - These are voltmeters(no matter the actual use) usually are connected to 6 or 12v(important!) and use a sensor that provides a variable resistance.

  3. Stepper motor - In the early to mid 90's stepper motor driven gauges began to appear, such as the Switec x.27 There are libraries available for the Switec but I don't know for any others.

Your car was manufactured during the transition era and so could be either of the last two. If it is electrical you need to determine if it is 6v or 12v as many companies used a 6v regulator just for the gauges. If it is a stepper driven unit you will need to identify which one you have.

6

Hutkikz:
Your car was manufactured during the transition era and so could be either of the last two. If it is electrical you need to determine if it is 6v or 12v as many companies used a 6v regulator just for the gauges. If it is a stepper driven unit you will need to identify which one you have.

The gauge is powered with 10V, and from fuel sensor related listings on ebay i deduced that it uses a resistor card for variable resistance.

7

As for now it turns out i cannot test out PWM or anything, because my Arduino had to be sacrificed to switch an inverter on/off automatically, so I'll bump this thread in a few days when a replacement arrives.

8

I hope you are not using UNOs - very inconvenient form factor for a real project. :astonished: Nanos much more practical. :sunglasses:

9

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