Vehicle Speed Sensor

[MegaMicra]

My speed sensor is a hall one. It's the oem one on the gearbox. I'm using an MS3X so I only have a single PT4 input which looks for 0-5v and doesn't have the pull up resistor like most of the other inputs have, (that's why I added the 1k resistor from the 5v tps ref). I have made sure that the sensor gnd's only at the Megasquirt sensor gnd connection to eliminate any noise.

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[MegaMicra]

So guys as this is all now working I ve decided to make a Raspberry pi 3 dash. My VSS is a hall device powered by 12v. The signal wire goes directly into my instrument cluster to work the speedo. A second wire that has no pull up then comes out of the instrument cluster which if you've read back somewhat you'll know I've pulled up to 5v using the tps and connected it to PT4 input.
My question is that if I remove the instrument cluster that second output no longer exists. Could I just connect the initial VSS signal output from the sensor (even though it's powered by a 12v source) to my PT4 input wire that's pulled up to 5v.
Im not really explaining it well so sorry for that.


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[MegaMicra]

I'll reword it eh. Can I use a 5v pull up on my signal wire, even though the sensor is powered by 12v. I'm only asking as I don't want to damage my PT4 input.

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[jsmcortina]

Yes.
On most sensors, the 12V powers the internal electronics and an external pullup to whatever voltage you want is used.

James

[MegaMicra]

Brilliant. Thanks.

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