backup fuel gage using same sender$

[Glombard]

I have a resistive fuel level sender driving a stewart warner fuel gage. I'd like to leverage the same sender to give fuel level on my Skyview Classic. I could connect the terminal on the back of the stewart warner gage to EMS pin 22 (I think) as a voltage input. between that terminal and ground would be ~2.5V for Empty and ~0.3V for full. That means voltage decreases as fuel level increases in this setup. Will the Dynon system work with a voltage that's inversly proportional to fuel level, ie a negative slope to the calibration curve? I would like to keep both the steam gage and have fuel level on the dynon if possible, but would prefer not to add 2nd sender to the tanks. Is there another way to accomplish this?

 

[Rhino]

Not sure if you can change that in the settings, but you could invert the voltage going into the Dynon, if you're willing to tinker a bit. A simple comparator IC or common emitter transistor circuit should do it.

 

[Glombard]

Not sure if you can change that in the settings, but you could invert the voltage going into the Dynon, if you're willing to tinker a bit. A simple comparator IC or common emitter transistor circuit should do it.

I wondered how difficult that would be. I’m not an electrical engineer so those circuits might be a little over my head, but if they are as simple as you suggest I suppose I might get there with a little research.

 

[swatson999]

Or, you could just try it. Connect it up one side, and use the Dynon calibration routine.

It's just a fourth-order polynomial that's stored in the config file...nothing that says it can't have a negative slope.

You can't break anything in the Skyview system by trying this.

 

[Glombard]

Or, you could just try it. Connect it up one side, and use the Dynon calibration routine.

It's just a fourth-order polynomial that's stored in the config file...nothing that says it can't have a negative slope.

You can't break anything in the Skyview system by trying this.

I think that’s plan A. If it’s a 4th order polynomial curve fit, that gives me some hope that it will work. I also wondered if I could use a custom sensor type and call it Fuel Level. I wonder if that would engage functions like detection of refueling to prompt entering the new fuel load.

 

[swatson999]

Any order polynomial > 0 will work. It's just a question of accuracy (since the curve is not linear, due to the shape of the tanks, dihedral, etc.).

(And assuming, of course, that Dynon's calibration function doesn't make some really dumb ass assumptions, like more fuel >>> higher voltage; but you'll know soon enough, and my money is on it working just fine doing the standard calibration per the installation manual).

 

[Rhino]

Make sure to come back and let us know if it works.