Build of a Honda CB125S (DIY Digital tachometer)

[ManuR]

Re: Build of a Honda CB125S

Hello

Thanks for the tip, i will look it up.
I have been busy with setting the timing on the µC. and other thing.

Couple of questions:
1 Is the engine rpm on a 4 STROKE measured ever revolution the Cam makes,
or very time the spark plug ignites (wich would mean: 1rpm = 2x cam revolution)?
when i know this i am going compare the spark against One phase of the engine.

2 But i have noticed that one phase gives a better signal then an other .. is my coil busted?

 

[AlphaDogChoppers]

Re: Build of a Honda CB125S

1 Is the engine rpm on a 4 STROKE measured ever revolution the Cam makes,
or very time the spark plug ignites (wich would mean: 1rpm = 2x cam revolution)?
when i know this i am going compare the spark against One phase of the engine.

Cam makes one rotation for each crankshaft rotation. Therefore, whatever signal is extracted would be at half speed. Spark frequency is one half of engine rpm if points are driven from the camshaft. If points are on the crank, (like would be the case for a 2-stroke,) the spark would fire every revolution.

2 But i have noticed that one phase gives a better signal then an other .. is my coil busted?

Doesn't sound surprising. It's all a pretty crude system.

 

[ManuR]

Re: Build of a Honda CB125S

I did the measurement with the scope.

One channel connected to the points,
the other channel connected to a random phase.
http://youtu.be/i-r9C0b-fUM

I made this from the video i recorded, because making a picture of my scope screen gives me nothing i could work with. here i watched the video frame after frame, and making my image myself 8)

Conclusion
keeping in mind that
1 spark = 6 periods on Phase
1RPM = 1/2 Sparks

1RPM = 3 Periods on Phase