I want to tap into the VSS wire in my car, and display in MPH on a simple LCD, i guess it could be segmented, i would only need 2 digits, i never go over 99mph, and i dont need deicmal points. My question is: is the vss wire analog or digital? what would i use to translate whatever signal this is? thanks for all your help. I know this feature exists on the Pioneer AVIC-N1 car stereo. -Ryan

 

Hi ryan,

What car are you trying to install this on?
I'm unsure about the form of the signal, chances are it's analog though.
I've been looking into tapping into my tach signal for my roof LED project. I dont have an oscilliscope though.

Have you searched the net for any schematics of this?

__________________
Jeff
To the optimist, the glass is half full.
To the pessimist, the glass is half empty.
To the engineer, the glass is twice as big as it needs to be.

 

My car has a governor that is set to the speed-rating of its tires. It stops the engine completely until the speed is reduced.
It only activates when I am passing somebody on a two-lane road and a big truck is coming at me. They say the governor is for safety. The tire rating doesn't have to match the car. Go figure.

 

2000 GMC sierra. I know there is a vss wire, but i have needle gauges, not a digital lcd gauge or anything, so i assume its analog. someone was saying that the wire pulses so many times according to the speed, i just dont know. -Ryan

 

Did a simple search for VSS on Yahoo and found the following on various websites and forums.

"The VSS outputs 40 pulses per driveshaft rotation and the signal is A/C.

The VSS signal has one side grounded at the PCM (VSS LOW). The PCM takes the VSSHigh signal and modifies into a square wave and outputs 4000 pulses per mile for use by the speedometer/cruise/radio and miscellaneous others."
(Talking about a GM vehicle.)

"The Vehicle Speed Sensor produces 8 pulse per rotation which a stock computer assumes 8000 pulses per mile."
(On a Ford website.)

"There are 4 types of VSS signals required by the ECM:
1. The two-pulse (2000 pulses per mile) square wave (D.C current or direct current) used on all TBI
engines thru 1992, all computer-controlled-carbureted engines, and on 1985-1989 TPI engines.
2. A four-pulse (4000 pulses per mile) sine-wave (A.C. current or alternating current) signal is
required by the 1990-1993 TPI, 1992-1993 LT1 engines, and 1990-1993 Camaro 3.1/3.4 V6
engines.
3. A 40 pulse per driveshaft revolution speed sensor used on 1993 and newer trucks with automatic
transmission, 1994 and newer rear drive cars with the automatic transmission
4. A 17 tooth per driveshaft revolution speed sensor used on 1993-1997 LT1 engines with the Borg-
Warner 6-speed transmission. An 11 tooth reluctor ring is used on 1993 LT1 engines with the
Borg-Warner wide ratio (3.35 First gear) 6-speed transmission."
(PDF file concerning Vehicle Speed Sensors.)

Hope this helps.
~Mike

__________________
All Electronic components run on smoke. Let the smoke out and it no longer works.
~Tim Baker (Electronics Instructor at John A. Logan College)

 

Well it looks like you found some agreeing information. Alright, so what do I need to read the pulses of a square wave signal to be able to convert that into a digital number?
Sorry, I'm a newbie here.