Wanted (Alive): Aftermarket vehicle speed sensor (VSS)
 

Brief history: I was using the VSS signal from my combination meter with the MPGuino but this had its drawbacks; with the ignition switch off, the combo meter shuts off as well, and that means the 'Guino thinks I'm going 0MPH. Not a huge issue though.

However, since I apparently fried my VSS sensor when I accidentally shorted it to the battery:eek:, I'm exploring my options.:D

I'm interested in finding an inexpensive 'always on' speed sensor, perhaps one similar to those used on bicycles. Do they exist? Could I use one meant for a bicycle and just dial in the VSS PPMs?

I tried searching the net but nothing's turned up so far. I think I just don't know where to look.

Thanks!:thumbup:

You'd have trouble with a bike speedo. Those things need the magnet mounted super-close to the pickup sensor on the fork. That works ok for a bike, but cars' suspensions take a much harder beating even on the simplest drive, that you'll surely lose or break it. You never ride a bike that hard because you'd drive the seatpost up your own ass.

That's my guess. I've never tried it. (the speedo, nor the seatpost)

Point taken.

Does anyone know where I can get a simple/cheap one made for cars?

Thanks!

The bike thing works, just kinda noisy (magnetic reed switch).

junkyard/autozone hall sensor (vss or crank position sensors), near a magnet strapped on the transmission output hub (with something on the opposite side for balance) would make the basis for a solid vss signal, though I wouldn't run it constantly even with the key removed.

A a kill switch is the typical way of dealing with issues relating to turning the key back. If the kill switch is a well positioned microswitch mounted on the stick shift then it becomes a very "natural" part of your driving style.

I might try this if I cannot find the VSS signal on my truck. A hall sensor looks pretty pricey ($75) at Autozone. The magnetic reed switch is $2. Either way some magnets need to get strapped on the drivetrain. Either should work with an MPGuino, correct?

reed switch switching 12 volts would work,

hall switch might need adapting since they are typically 5 volts.

Okay, I did some searching. Will one of these reed switches listed work? (Look below the foot switches). http://www.action-electronics.com/switches.htm
How exactly does this work, does the switch send a signal everytime the magnet passes?

Will the signal from an ABS speed sensor work for the MPGuino?

dunno, I was thinking of the bicycle computer type.

The other thing to keep in mind is that the speed signal is really sort of optional, your car already has speed and distance instrumentation built in. It takes a little mental exercise, but being able to keep track of your odo and being able to divide the indicated speed or distance traveled by the fuel consumption rate or fuel used, in your head, is something a lot of folks can learn to do. The thing cars don't usually have, except at fillup, is fuel consumption feedback, and the guino gives you both instantaneous gph and accumulated fuel used.

So one should weigh their ability to compensate for non-integrated speed signal with their ability to sort out an integrated speed signal. If that makes any sense.


Also from a "beat your high score" perspective, there are a couple strategies to simplify things.

if your commute is largely point A to point B, then check the fuel used on the "current" screen, and see if you are using more or less fuel to get to and from
work, and try different strategies and/or routes to see if you can get there with less fuel.

If you put the gph in the numerator, then it may be simpler to do the math, i.e. 10mph/.5gph = 20mpg, but it is a lot easier to do (IMHO) .5gph/10mph = .05 Gal/Mi and just try to beat your low score in that case.

Thanks dcb, I did not think of it like that. If I read the gal/hr and divide it into mph, I'll get mpg! If I can do the math that fast.
I am thinking about mounting some sort of optical sensor to read the driveshaft rotations. I might try a small variation on this: http://www.punkjob.com/OpticalIFs.pdf Not ideal, but I think with the right positioning it might work. If I can shoot the light beam to get interrupted by the yoke turning right behind the transmission...

I want to know about this too. Any inputs? Thanks. I have been thinking about this but I was pretty unsure of the answer.

thecheese429 has blazed the trail on "aftermarket" vss here:
http://ecomodder.com/forum/showthrea...s-13293-2.html

re: abs sensor, definitely maybe.

What about the old add on MPG computer and cruse control sysyem??

It takes a small coil and a pair of magnets on the drive shaft?

I understand you can make the coil by takeing the coil out of a 12 volt relay.

Rich

the coil doesn't make a sufficient signal at low speeds.

Well the one on my old Mileage computer worked fine down to 1 MPH...

I know the cruse controls were program not to work lower than say 30 MPH and many would drop out at over 80 MPH, but the speedometer always read.

Rich

Also we could double the magnets for a finer reading and more signal...

Rich

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! :D 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. :cool:

Homemade optical speedo signal FTW :)

Discovered one issue today. With a fresh coat of snow on the roads, the sensor wouldn't trigger the MPGuino. I figure the sun was reflecting enough light to mask what the bulb was putting out. When I hit a clear patch in the road, it'd pick right up again. Guess I need to stick that belly panel back on...