MickTheMechanic
commented
1 year ago Hi.
You need to ask yourself what will you use as a signal. How many times do you have this signal per cank rotation.
Number of signals per crank rotation * RPM / 60
So if you have a single cylinder 4 stroke then you will use the ignition coil driver as a signal, then you have one signal for every two rotations, so mathematically speaking 0.5 signals per crank rotation.
(A 2 stroke signle cylinder would have 1 signal per rotation)
Multiply by the RPM you want the shift light to be triggered at:
0.5 signals per rotation * 5000 RPM
= 2500 signals per minute
Then divide by 60 to convert from signals per minute to signals per second, AKA Hertz, AKA frequency
2500/60
= 41.6 Hz
Thats how it works :)
TechFreak9356
Hi there, I came across your project of a DIY shift light and I figured it would be cool to be able to install one like this to my single cylinder motorcycle. I would like to learn more and better understand how the code works, especially in detecting the engine RPM through frequency from tach in or crank position sensor or magneto pickup, etc.
I am trying to adapt your project to my single cylinder but I can't quite figure it out, or to be exact....not sure of how the frequency is calculated and/or measured, since your project is originally for 4 cylinder cars. I'm not that familiar with engines, and googling only made me more confused as well so I was not quite sure with my understanding of the frequency measurement.
EDIT: My motorcycle is only a simple 150cc single banger with a simple carburetor and aftermarket CDI unit. My tach signal is taken from the ignition coil positive line, which for some reason, my digital dash cannot pick up (only an analog, pointer-based one picks up the signal, my stock CDI then was detectable). Although my aftermarket CDI has a dedicated tachometer out pin, my digital dash reports a lower RPM value from there (the analog cannot pick up the signal from that pin though). I dont have any idea about it yet but the seller of my digital dash managed to give me the specifications of the dash unit: The RPM Calibration for 1/2 Cylinder is 16.6Hz @ 1000RPM, 4 Cylinder is 33.3Hz @ 1000RPM. The 2 cylinder calibration works for my motorcycle with the stock CDI unit, and is accurate, but all of the aftermarket CDI units I tried aren't recognized (possibly due to higher power signal? not sure). But if this one might not work with tach signal from the Ignition Coil positive line (say the power or voltage is too high), I'll then have to math myself off to adapt the arduino to the lower tach readings from CDI tach pin so the shift lights still look accurate and sync well with the analog tachometer.
Any help would be appreciated, thank you