Fuel light - Suzuki GSX-R Motorcycle Forums Gixxer.com
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post #1 of 3 (permalink) Old 05-28-2019, 01:23 AM Thread Starter
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Fuel light

I’ve got a Translogic dash which doesn’t have any input for low fuel other than you setting a mileage and resetting when filling up. I’ve tried searching but can’t find any info. Is it possible to wire a led to the fuel sensor to show like the factory dash would? Thanks
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post #2 of 3 (permalink) Old 05-28-2019, 09:07 AM
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Re: Fuel light

It looks like the fuel level sender is just a potentiometer on your model, so you should be reading a certain resistance for a certain fuel level between the B/W and B/Lg leads. A table in page 9-33 of the service manual lists a couple of resistance values to give you an idea of what to expect, but they should be easy to map out with a DMM. Wiring up a circuit to light an LED when the resistance crosses a threshold shouldn't be too hard, although it would require some circuit design experience, but the main problem would be that the sloshing around of the fuel inside the tank would result in the light going on and off constantly without appropriate smoothing.

In short it shouldn't be too hard to do, but it's not straightforward (unless you can find an off-the-shelf module for the job). It would require some experience with EE design and/or microcontrollers and even then you should expect to have to do some R&D for it to perform acceptably.
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post #3 of 3 (permalink) Old 05-30-2019, 09:15 PM
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Re: Fuel light

If you want a smart, over-complicated solution, might be worthwhile to find hobbyist electronics forums and asking questions. Look up the table on 9-33 and look at the resistances and then take that info to the forums and look into threads where someone made a warning light for a certain voltage value over time.

Something like this: https://forum.arduino.cc/index.php?topic=183046.0

For an analog low fuel light, you could use the following:

A stranded length of 24 gauge wire (think that's the OEM gauge, that's what my wire strippers told me, anyway),
Connector pins for said gauge,
an "'X'-Volt opening" diode,
an "'X'-Volt" LED.

How to do it:
First, you need a value of voltage value between the "send" side of the float sensor to ground at a particular level. The manual specifies a float point of 2.22 inches for a particular resistance reading, so I deduce that that fuel level is "low fuel" and the light comes on in an OEM gauge cluster, so let's just round it to 2 1/4 inches. Measure the voltage at idle, 5000 rpm, and maybe 8000 (shouldn't rev higher in neutral) with the fuel at 2 1/4 inches. Average that reading.

For the purposes of simplicity, let's say that the average voltage reading from the "send" side and ground at "low fuel" condition is 4V.

Time to make a low fuel light:

Connect a length of wire to the "send" side of the fuel float sensor output.
Connect the other end of that wire to the NOT STRIPED end of the diode.
Connect another length of wire to the STRIPED end of the diode and the other end to the LED.
Connect the other side of the LED to ground.

What will happen is that the resistance on the float sensor will lower as the fuel gets lower. Once the resistance drops enough, there will be "X" volts between the send side and ground. For the sake of simplicity we called it 4V. If we bought a 4V diode and a 4V LED, whenever the voltage output of the float sensor hit 4 volts, the diode will allow current to pass and it would light the LED. If it flickers, that's fuel sloshing around. If it becomes steady, you are below 2 1/4 inches.

Note: most LEDs are rated for 5V, so finding a "4V" would be difficult. Using a 5V LED just means that it will be dim at 4V. Maybe using a 5V diode with the 5V LED would give you more warning for low fuel since the resistance of the float decreases with fuel.

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