I have a 1978 1275GT Austin Mini and would like to replace the existing magnetic speedometer mechanism with a stepper motor(?) based setup as the gear ratios and wheel diameters are now non-standard and the speedo is way out- recalibration of the speedo works out around $150+ (£100++)
the use of an arduino either:
(i) taking a pulse from a driveshaft rotation (via a hall-effect transducer)
(ii) using an optical trigger off of a rotating disc on the end of the speedometer
and then moving the original needle around the existing gauge would enable me to use the existing kit but display an accurate speed as well as potentially allowing the odometer to function if the rotation rate of the cable or the driveshaft could be converted into a drive for it
Possibly the alternative is to control the speed of a motor that was intermediate between the speedo cable and the speedometer?????
I think probable controlling the rpm of a small motor might be easier as a multiplier could be used between the two speeds?
What are your thoughts?