My Peugeot 504 speedometer came to an end, with a wire & wobbly needle. I don't like it anyway.
I made an LED RPM gauge
before. I think an LED speedometer would be fine too. The main obstacle for me was the speed sensor. I thought of using variable reluctance magnetic pick up sensors or automotive ABS sensors. They operate on the same principle, fixed sensor over a rotating toothed ferrous wheel. As the teeth pass by the sensor, up & down electrical impulses are generated, as the speed increases, the frequency goes up too. Then we need to convert this frequency to voltage (using the LM2917 as in a tachometer), the increasing voltage will drive 30 LEDs through 3x LM3914 ICs. Good
I didn't spend much time looking for ABS sensors. I had a stepper motor from an old inkjet printer. I tought it can generate similar signal to be interpretted by LM2917. Later I found this motor can generate increasing voltage as the car speed goes up. So, I don't need a frequency to voltage converter (LM2917)
What to do:
1- remove the old speedometer with its wire
2- mount the speed sensor underneath the car to get movement from where the old wire got it
3- building the circuit