I did a similar thing some years back when building an alloy tank. I
used a series of solid-state liquid level sensors (data sheet attached)
that incorporate a photo diode and photo transistor moulded into a
polysulphone housing. The domed end uses the simple effect of total
internal reflection to either switch the transistor on or off depending
on whether it is immersed or not.
I mounted mine in tapped bosses on the surface of the tank, but these
could easily be built into a "dip-stick" and mounted from the top of the
plastic tank. Just another variation on a theme.
Nigel
On 17/06/2014 15:02, Andrew Sarangan wrote:
> I will take some photos and write up some details in a few days.
>
> The idea was based on what I accidentally observed one day when
> holding a flash light to the fuel tank. When the flash light is held
> below the fuel level, the entire fluid lights up. When the flash light
> is above the level, the tank lights up. The contrast across the fluid
> level is about 10x. This is due to light being trapped above or below
> the level. See attached pictures.
>
> So, I made a board with four LEDs in a column, and another board with
> 10 photodetectors in a column. Using a microcontroller, I am flashing
> each LED in sequence, and then computing the liquid level based on the
> measured contrast. The output is displayed on a 10-bar display. The
> LED board will attach to the aft of the baggage bay bulkhead, with
> four holes to allow the light to get through. The detector board has
> to attach somewhere on the front side of the tank. This might be the
> tricky part because I need to make sure it is secure, but also
> removable and does not interfere with the controls.
>
>
> On Tue, Jun 17, 2014 at 5:52 AM, Kingsley Hurst
> <kingsnjan@westnet.com.au> wrote:
>> <kingsnjan@westnet.com.au>
>>
>> Andrew,
>>
>> What to do about a fuel gauge has been a bone of contention for me. I would
>> very much appreciate your sharing how you made your device.
>>
>> Only thing is, can your set-up be accomplished AFTER the fuel tank and
>> module are installed?
>>
>> Thanks
>>
>> Kingsley in Oz.
>>
>>
>> -----Original Message----- From: Andrew Sarangan
>> Sent: Tuesday, June 17, 2014 12:15 AM
>> To: Europa List
>> Subject: Europa-List: Noncontact fuel level indicator
>>
>>
>>
>> The fuel tank is translucent. One can clearly see the fuel level by
>> eye. So, it occurred to me why not build a fuel level sensor that
>> attaches to the outside of the tank? I recently built such a unit with
>> LED illuminators and detectors, and it works like a charm. It even
>> shows the waves when the fuel is sloshing around. Only question is,
>> how does the translucency of the tank change with time? If it becomes
>> totally opaque in a few years, then this won't work. I can post
>> further details of the device if anyone is interested.
>>
>>
>>
>>
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