At last, I got a VSS rigged up on my truck. The factory VSS did not provide a signal that would trigger the MPGuino. After much trial and error, several attempts at trigger disks and lights, I have a working solution.
I used a piece of black corroplast, cut to about a 5 or 6 inch diameter disk. I then cut it from the edge to the center just so I could slip it over the driveshaft. I then made small cuts from the center, probably 8 in total counting the first long cut. I then cut 4 rectangular windows about an inch in from the outer edge, spread evenly around the disk. Any more and I didn't think the light sensor would do a good job picking up the signal. To clamp it to the driveshaft, I used a hose clamp. Had to reposition a few times to try to get the disk clamped evenly, and rather straight. I also had to run a zip tie to straddle the long cut I made, and looped it through the two closest holes to cinch it together a little more evenly.
I am using an ordinary cockpit gauge bulb, 12v, as the light source. It is hard wired into the cigarette lighter circuit, which is a switched 12v supply. The light sensor is an IR sensing LED from Radio Shack, p/n 276-145A NPN Silicon Infrared Phototransistor. I tried using phone cord for wiring, but ran it too close to the exhaust and had a meltdown. I have since replaced that with CAT-3 wiring, which has 6 wires instead of 4, and they are solid conductors, instead of braided. Worked better for me when positioning and soldering. I used 3 (red, black and green) for the light and sensor. Both share the red, the bulb uses the black as ground, and the sensor uses green to go back to the MPGuino...and to ground.
Installed pictures attached. Sorry, it is nighttime, and I used my phone. If needed, I can provide better pictures later.
And...ops checked good!
Got the VSS signal set to 19360. 4 slots in the disk, 33 inch wheel/tire combo, and 5,280 feet in a mile. I will still keep eye-balling the fuel flow, as I have been driving that way for a year now.
