Gary Johnson wrote:
Kirbert wrote:
I just realized that the two wires to the “pulse generator” in the
diff that provide a signal to the speedo are a signal wire and 12V
power. I was a little surprised that this thing needs 12V power. I
expected it to be a coil-and-magnet type of affair, generating its
own signal with no need for a power source. Can someone elaborate on
such a scheme?I will take a stab at this, someone can shoot me if I am wrong..... It sounds like the device might be a VSO (vane switched oscillator). This device are triggered by ferrous metal. Basically a proximity switch. They are available in two and three wire configurations. If the two wire style, the 12v that Kirby is talking about must be pulled up using a resistor between the 12v and the device. This allows the 12v line to also act as the switched line. My guess says that the 12v is coming from the trip computer and it is pulled up inside (I dont have the schematics so this is a guess). Here is the basic Circuit Idea...... 12v | | ----- | | | R | Pull Up resistor | | ----- | +------- Switched Line (This point would mesaure 12v with no metal present) | This output would be in the form of a pulse train fro 0 to 12v that | varies in frequency as a function of speed. ----- | V | | S | Detector | O | ----- | | | ----- --- - My Two Cents..Regards,
Gary
'86 XJ-S 45K“Flame Suit Enabled”
Gary,
This is also a comment on the proposed circuit. The value of the pull-up resistor also
acts on the pulse width.
In the note to Walter Petermann I suggested that the only way we will resolve this is
to test an ailing Jaguar. But, most of all I wanted to thank Walter for donating his
expensive time and expertise to this effort. We bargained him down from $85/hr US to
$0.0 US with a one year guarantee of all work performed.
Ned