Mechanical speedometer drive solution

[nsocwx]

I found an encoder motor on amazon and removed the 10:1 transmission from it to get a 6000RPM motor. After finding that didn't quite have enough torque I made a 4:1 gear for it, but the noise was pretty intense as I don't think it was perfectly round. This motor in particular does 12 pulse per rotation, 120 if you leave the transmission on.

I see what you mean about the VSS signal, it seems like you're kinda stuck on that. In my case I'm reading a 4000 PPM signal from a Holley Terminator and the low speed resolution of that seems to be acceptable. It's a PWM- output so I'm having to use a pull-up resistor circuit and interrupt on the descending change (this thread). I do notice some jitter where one cycle may catch 1 more pulse than another changing the speed by a few MPH. On that front I might suggest calcautating the frequency given method 2 shown here in the video. They count millis between pulses to calculate the frequency immediately and it can be updated with every pulse.

Funny that you mention the LM2907 I just came across that in my research today. I was having an issue understanding how you might calibrate the readings from that device and I also didn't see any prebuilt PCBs. I'm also not reading directly from a sensor.