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Old 08-01-2008, 04:56 PM   #1 (permalink)
needs more cowbell
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VSS Signal assistance?

Is anyone in a position to capture the vss signal on a reed switch car (metro, starion)? My scope is on the fritz.

Problem: The vss is too noisy on some cars, need to know what it looks like in order to filter it properly. Plain old debouncing won't work because it seems the vss pulse peak to peak duration is less than your typical debounce period (was seeing 8342 microseconds @53mph, typical debounce is like 20000 microseconds). I added a tiny bit of debounce (3ms) and was able to put a more normal vssPulsesPerMile figure in, but the instant reading is jumpy.

It isn't a problem for hall effect cars because that is not a noisy physical switch.

I wonder if there is noise from the electromechanical parts of the speedometer/odometer? I don't know if I can defeat this problem with software alone. But would appreciate any insights into how to fix this.

Anyone seen a metro ECU schematic? Maybe someone has an old one I can dissect?


Last edited by dcb; 08-01-2008 at 05:29 PM..
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