Converting fuel level signal to display on tachometer

Projects General Guidance
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Hi all

Very new to all things Arduino though nothing better than a project to get started.

I've a vintage scooter (1977 Rally 200 vespa) that has very limited instrumentation.

I'm adding a fuel gauge which I'm hoping to use an existing tachometer readout to display the values.

For the fuel level signal I'm using this pressure transducer which is designed to work with a standard fuel level gauge at a variety of resistance values.

Whilst I could use any aftermarket motorbike digital dash I'm hoping to keep it looking reasonably stock and use this aftermarket dash designed for my scooter.

https://www.sip-scootershop.com/en/product/speedometer-rev-counter-sip-20_50000630

Unfortunately this doesn't have a fuel level readout, though does have a tachometer area that I won't be using.

So wanting to check the feasibility of converting the fuel level sender signal to a signal that will display say 10000 for 100% fuel and 5000 for 50% etc.

The fuel level sender has some smarts so I can set the values for 100%, 50% and 0% (as tank not linear) so that should be quite accurate and stable.

As the fuel sender signal works off resistance and the tacho off frequency I've no idea if this can be done.

Thanks so much!

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The sender manual states it outputs a PWM signal.

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I would first tackle interfacing this signal and reading the PWM value in the controller. Then you've got to convert that to a corresponding frequency for the tach input. DO NOT connect the output of the sample circuit directly to your Arduino! Do connect the GNDs of the two circuits together.

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Hi Doug

Thanks so much the details, that makes a whole lot more sense!

Am I correct in thinking that the arduino can only use a signal up to 5V, would this mean I'd need to apply a resistor to take the signal below this?

Also would love any advice on the best arduino to get for the project? There's plenty of places to house an enclosure etc and I've a stable supply power available as have a Motogadget m-unit setup which I can run it off as an accessory etc.

Thanks again

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I'd use an optocoupler for safety. Also no need to connect the grounds that way. The signal is 100 Hz so no problem for a PC817 or similar opto, and it gives complete isolation.

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