Best would be if it could handle pulse, but it can only handle analog input.
Is there anyone who have a good solution?
tried using frequenzy to voltage adapter but the speedo is jumping too much.
tried an tachogenerator, 7v/1000rpm , better but still, needle is jumping.
any answers please.
Attached is a schematic which I devised for exactly this task. Also attached is a veroboard layout. It should work fine with a needle gauge in RD. My VSS / gearbox / road-wheel-size combination gives 8000 pulses per mile. You’ll need to alter R4 / C4 values if your car is much different. The output needs to be less than 5v to suit the Dashbox analog inputs.
Just for interest, my situation was a little more challenging as my dash uses a text gauge for mph which brings an additional problem that no matter how “smooth” the analogue signal there is still jitter in the gauge output whenever the speed is exactly on the integer boundary e.g. if the speed is exactly, say, 60mph the display will flicker between 59 and 60. I had to arrange for the display to refresh no more than once per second.
Also just for interest, part way through developing my dash I abandoned the Dashbox because it did not have quite enough digital and analogue inputs for all the additional sensors I planned to fit to my car. I could have worked around that with a multiplexer in front of the Dashbox but but with that in addition to the mph interface I felt my project was getting a bit messy, so I built my own Arduino Nano + 16 channel mux “dashbox”, which also allowed me to provide two pulsed inputs.
I’m in the process of replacing my Dashbox with a home-made equivalent which calculates MPH from the period between VSS pulses and will also take care of smoothing / refresh rate, however I’ve dug out the attached from the previous, Dashbox-based, dash which more or less shows how I used a trigger to get the once per second refresh.