Bike fuel level indicator

[husoi]

Since I got the Shadow I had to rely on a temperamental light that could or not go on when the fuel goes low.

Because the distance to empty greatly varies with riding style, speed etc. guessing how far I could get would result on either filling up with half tank or, as it happened not long ago, or pushing the bike for 200 yards to the station. 

I've been looking for anything that would work as a fuel gauge. However, most are too big and won't fit in the tank.

So, it was time to think outside the box...

 

After weeks of investigation I found a model that could work.

For that I would need some parts and to dig my electronics' tools.

 

Obviously I won't need all of these, they are lots of different parts to be used.

 

Yesterday evening I managed to create a prototype (working one ).

The idea is to have the display LED's fitted on the handlebar while the "brain" will be safely located elsewhere.

In this pic the tank is represented by the wee bowl with water.

When immerse the LED's will light up.

 

Next steps, transfer the circuit onto a permanent IC board and finding a fuel resistant wire that will be fitted inside the tank with the sensors.

[Gerontious]

try it with petrol in the glass.

Edited July 21, 2021 by Gerontious

[fredc]

 

petrol is non-conductive

use a dipstick

[husoi]

I'll be running 4 wires inside the tank to connect the sensors.

Although, as you say @fredc petrol is non-conductive I don't want to risk the cables moving around and not only change the position in the tank sending false information but also connect to the tank wall and create a short-circuit.

 

So far I found out that a good contender is PTFE insulated wires and having the soldered connections covered with heat shrink PTFE tube.

To hold the wires and sensors in place I'm thinking of some stainless steel cable like this.

https://www.diy.com/departments/diall-stainless-steel-cable-l-10m-dia-3-5mm/1521256_BQ.prd

The biggest problem I'll have is to fix the cable at the top next to the cap.

The bottom will be going all the way down to the secondary tank so holding it there won't be an issue as it will be passing through the short connecting hose.

 

My plan is to have the lower sensor on the upper side of the secondary tank, the 2nd sensor just above the bottom of the main tank, 3rd sensor halfway the main tank and sensor 4 close to the top (around 2in from top).

[Jerry1111]

If you use PTFE wires, you're measuring capacitive coupling between them. What's the Df of petrol? Will it work?

Also, have at least a cursory read of ATEX - you don't want to be trapped in a situation with an empty tank, some oxygen inside, a wire sparking because of some little inductance somewhere... It's not nice!

[husoi]

PTFE wires are the only ones I found that are chemical resistant.

Adding to this I'll be using PTFE heat shrink tubbing to improve insulation and minimal naked wire exposed to fuel.

 

The device won't be measuring capacitance between the wires, only one will have a very small current (in order of 5mA - 0.005A) that is far from capable of creating a fire.

The sensor works on resistance the same way as the current thermistor that is fitted to the fuel light. This means I'm not adding any risk.

Because voltage at the sensor is less than 3V (max value) there is no risk of fire/explosion so ATEX rules don't apply.

This opposite to the 12V that a normal fuel sensor have makes it safer than standard OEM fitted one.

The sensor will be connected to the "brain" and subject to less than 3V as above and the other end will be grounded minimising the risk even further.

[S-Westerly]

One thing which I'm sure you have considered but would this count as a modification to the bike for insurance purposes if god forbid you had an accident?

[husoi]

I would argue that is an added gadget and not a mod.

Similar to an USB charging port. An insurance company won't discard responsibilities because you  have a charger.

Even if they would argument with the use of a phone whilst riding, which is illegal for phone calls or texting, makes the installation of a USB charger illegal.

This argument becomes redundant when the phone is used as navigation device.

[Ian Frog]

Knowing what insurance companies are like !

If they believe you have made any alteration in the fuel storage area I believe you will have more chance of getting pregnant than getting paid out.

Even worse if god forbid any flames were involved.

I believe this would apply to anything like this which I suspect is why there appear to be no manufacturers doing aftermarket fuel level gauges like there are doing gear position, gear selection etc.

I may be wrong but I would be interested in others opinion.

Cheers

Ian

[S-Westerly]

Think you'd need to talk to a loss adjuster and get his professional take rather than random opinions. Personally I'd not take the risk but that's my own judgement. As it is my bike has a perfectly adequate fuel level display so not really an issue for me.