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Just a quick one to share my over-engineering of a simple problem. I’ve got an unmatched/inverted fuel sender to my smiths gauge. The sender is the Cortina type with integrated fuel pipe so it will be a bit of a pain to replace. My options were either: Make do and fill up when my gauge reads full. Get the reliable, tried and tested, aftermarket gauge matching unit for £40-50 Over engineer my own solution for around £10. Over engineer it is!! The Bits I needed: Arduino nano (chinesium one) £3.50 ish eBay 1k digital pot (SPI controlled variable resistor) + dip convert board £4.00 ish eBay 1k pot (thumb turn) to simulate sender £0.50 ish eBay 1k trimming pot £0.50 eBay LED - liberated from an old pc. £0 Resistor - found in draw £0 Connector strip - in an old biscuit tin £0 Perfboard cutoff £0 A very basic overview of assembly. The trimming pot with the thumb pot (sender pot) are arranged as a potential divider to an Arduino analogue input to read the sender value. The digital pot is connected to the Arduino via the SPI inputs, the digital pot will be connected to the gauge. LED connected to a PWM output on the Arduino via a current limiting resistor. This together all looks like this: Programming the Arduino: The basic function of the Arduino is to read the resistance value of the sender, apply a function to give the desired resistance value and set this value to the digital pot which is read by the smiths gauge. I’ve decided to utilise some of the Arduino power and apply an anti-slosh function to smooth the resistance output. This function reads the input value every 100ms for 3 seconds and outputs a rolling average to the gauge. You can also output values from the Arduino to a laptop via USB serial. You can see the smoothing in the graph below. This will also be handy when I get round to setting this up to the actual sender unit. I twiddled the pot to simulate a bit of slosh in the tank (not inverted the output yet): The arduino can also activate the led as a low fuel indicator. the first stage turns on the led and the second stage (on fumes) pulses the led. the board has pwm so why blink when you can pulse! This will all be programmed to suit the tank. The next step is to get this fitted to my gauge and make sure it doesn't let the blue smoke out of my digital pot!
