As can be seen in the video, the needle movement has a slight delay. I thought about updating the input frequency more often. I found that it is impossible to read a 1Hz signal more than once every second. I chose to use the 2000ppm signal, the 128kppm signal would work better. Discussion here:
https://forum.arduino.cc/?topic=731339#msg4921311 I’m sure I learned about that in school once…
I also wanted to eliminate the values on the right side of the decimal point to reduce fluctuation. That’s not good for the 2000ppm signal, but entirely possible with the 128kppm signal. For the 2000ppm signal, some values require the decimal places, example: 9mph at 5.00Hz, 10mph at5.56Hz, 11mph at 6.11Hz, 12mph at 6.67Hz, 13mph at 7.22Hz. Where the 128kppm signal values have a greater spread: 9mph at 320Hz, 10mph at 355.55Hz, 11mph at 391.11Hz, 12mph at 426.66Hz, 13mph at 462.22Hz.
The Needle jump at start may be from the PID comparing the previous value to the current value. If the previous value is zero(not moving), the difference is greatest. I may be able to pre-load the previous value to trick the PID into behaving nicely at start-up.
The noise coming through the stereo may be suppressed with a coil, or capacitor on the motor supply.
I’ll rewrite the code to use the 128kppm signal, work on eliminating the start-up jump, and try a capacitor on the power line. After that, I can work on my youtube video skills and try to get a better view of both speedometers side by side.