HELP! Eratic RPM readings using Magneto on small engine

[DanDietzen]

We have been trying for several days to get a setup that will give us good tach (RPM) readings with a magneto. Nothig seems to work, we have even been modifying code.

Does anyone know what is the different between the tach inputs on MS 1 and 2? We have several of these 10 HP single cylinder mag fired engines running on MS1 boards. They run great with good, acurate, steady RPM reading. MS2 - the reading is all over the place, we can't seem to get a sensible reading at all. shows over 5000 RPM just cranking! (sometimes). Goes to 22,000 RPM as soon as the engine fires.

The maddening thing is that we havn't changed the main board, just added the daughter board, so the electronics is the same and external wiring is the same. Perhaps the interupt on the MS II is different, or the code itself is different.

Using V2.2 (green) boards. V3 code and V2.25 MT.

Can anyone shed some light on this?

[Bernard Fife]

Perhaps the interupt on the MS II is different, or the code itself is different.

DanDietzen,

Certainly the code is different. And MS-II is runnning much, much faster, given it more opportunities to pivck up false signals. Have you tried experimenting with the next pulse tolerances?

Lance.