I'm
restoring restomodding a 1972 Volga 24 currently and i need to modify the original mechanical speedo to be controlled electronically.
The original engine and gearbox are shagged so i'm swapping a SAAB B204 with a different gearbox, which is why the speedo needs to be modified.
Also i want to preserve the original look, which is why i'm not going to put a screen in place of the speedo.
It's a strip speedometer, which presents it's own challenges.
I'm thinking there's two options right now.
First one is an external speed controlled motor, which would spin the cable input in the speedometer. I think this would be the least intrusive method but it might be a bit noisy depending on how it's done. Also i would be relying on the original mechanism of the speedometer to work and be accurate.
Second would be to tear the speedo apart and connect a stepper motor directly to the mechanism that moves the needle but this would be most intrusive. Of course this way the speedometer needle would be directly coupled to the stepper so i think reliability and accuracy would be better.
Also there are other gauges on the speedometer cluster, such as oil pressure, battery charge/discharge and fuel level, which complicates things, because none of the original electrical system will be left in the car and it would be nice to have these gauges work.
All of these are regular gauges and can be driven directly with PWM from a microcontroller but then i would need to interface remote sensors and i start diving down a bit of a rabbit hole full of CAN and diff pairs.
Would be nice to have some input before i blow this project too far out of proportion with feature creep.