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Old 04-22-2021, 09:46 AM   #8
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Join Date: Jul 2016
Location: MA/NH

Originally Posted by Wobsmangbaffler View Post
How are you measuring the car speed? I am currently doing a similar project but it is only for measuring the speed of the car, and not inputs from LH / EZK.

The technique I used was:

- Take sine wave signal from rear axle

- Filter through a full bridge rectifier to make it all positive voltage

- Use capacitors to smooth the pulsating signal into a smooth voltage level

- Use analogread() to measure this average voltage, which correlates to vehicle speed

Does LH have a different way of measuring vehicle speed?

Interested to know!
if I recall, the VSS sensor in the diff produces an AC voltage that is wired to the cluster speedo/odo. Inside that there is a UAF2115 chip which converts the AC frequency to a open collector signal that LH weakly pulls high and counts when it is pulled down. It'd probably be best if you counted this post processed signal instead of trying to process the AC voltage yourself. The AC from the sensor is pretty high, I have measured over 90 volts from it with a high impedance meter.
1991 244 LH2.4 M46 352k miles
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