Low Fuel Light

The Gooster’s  low fuel light was developed by my good friend, Robert Pugh. Here’s the details.

The circuit takes four main inputs / outputs, as shown below:

In my application, the resistance across the fuel gauge is 142 Ω, and the fuel sender has a range of 14 Ω when full to 264 Ω when empty. We decided that the light should come on when there was 

1/8th of Tank of fuel left, and that there should be an adjustment range of approximately +/- 25% of that 1/8th of a tank.

From that, Rob came up with this (click to download):

Based on these calculations: Fuel Light Circuit Calculations.pdf  Low Fuel Signals.pdf

From that we developed a vero / stripboard layout for the circuit (click to download):

Red squares denote track cuts, and the blue lines are wire links across tracks. The black circles are pin / jumper / terminal block points. The terminal blocks I used had wider spacing than the tracks I had designated, so my board has some extra links for the zero volt & lamp negative lines.

A full list of parts and their order numbers from Maplin and Farnell can be found here: 

Low Fuel Bill of Materials.pdf

Pictures and video of the circuit in action can be found on this blog entry HERE.