View Full Version : calling electrical gurus
bensenvill
03-22-2005, 08:30 PM
ok so I want to put some of my digital electronics education to use and make my own digital speedometer display.
can anyone point me in the right direction on how to access the speed sensor [or a sensor I can add]?
megail
03-22-2005, 11:21 PM
oooh, this is gonna get interesting. my guess is first find the sensor so that you know what you're working with and then find a good ground and power for your digital...but other than that i'd ask excelcier.
Excelcier
03-23-2005, 01:24 AM
VSS Speed sensor is in the radio harness for the stock radios that have speed sensitive volume. There is a small connector with a single wire on it. If memory serves, it's a grey wire. This will be a square wave that increases in frequency relative to the cars speed and is a TTL 5V as logic 1.
bensenvill
03-23-2005, 01:26 AM
ya the title was aimed squarely at excelcier.
I'm very limited by the fact I know nothing about car electronics. I'm probably going to do this with some pic programming [or whatever chip works I have laying around], I'm assuming the speed sensor outputs a pulse width modulated signal.
I just need some more info on exactly how speed sensors work.
bensenvill
03-23-2005, 01:30 AM
[wow and I get my response while I was typing mine]
I totally forgot about that volume adjust feature... so that offers the full speed signal? Any clue what frequencies are at certain speeds? [I no longer have an oscilliscope]
Excelcier
03-23-2005, 01:35 AM
By the Ford spec, the pulse frequency is 8000 pulses / mile. You can use that to calculate the speed.
bensenvill
03-23-2005, 03:00 AM
sweeeettt... mucho appreciated.