Analog Speedometer

Has anyone had any luck installing an analog speedometer? I suppose it would be fairly simple to run the vehicle speed digital data through a D/A converter and drive a meter (which would have to be calibrated), but I haven't done the research yet. Probably never will get to it until the first $300 speeding ticket.

It would be better if there was a mechanical port in the transmission, but there probably isn't one.

In my '05, I cannot see the display on a bright day, especially when driving toward the sun. My polarized sunglasses really wipe out everything. The display in my wife's 06 is larger, so the problem is not quite as bad, but still iffy.

 

Close but no panatela

No. not this kind. I don't mean a dash-mounted full-size speedo for a race car cockpit. I had in mind more of a very small VDO-type 2-to-3 inch speedometer or even a (for example) 270-degree 0-1 milliameter to which I could I could add a few MPH markings. The best would be a small electronic ANALOG meter with MPH and (optionally also KM/H) already marked. I probably need to mark only 25, 40, 55, and 70 MPH; the rest could be interpolated.

The object is to be able to check (approximate) vehicle speed while wearing polarized sunglasses and driving toward a patch of bright light. The entire display - yes, at full brightness - becomes invisible under those conditions.

I'm thinking maybe the tiny little triangular window on the driver's side would not be a good place to put the speedometer because of the side curtain air bags. I'd really hate to survive a crash only to be killed by a speedometer to the forehead.

My wife WOULD put that on Bizarre News.

Thank you for the suggestion. I'm still looking.

 

Siemens-VDO also has speedometers in 3-1/8 and 3-3/8 inch sizes:

http://usa.siemensvdo.com/products_...do-performance-instruments/instrument-series/

I was looking for 2-1/6 inch size, but that doesn't seem possible unless I use a generic meter not marked in mph and/or km/h.

The installation manual for VDO shows hookups for a magnetic sensor, an inductive sensor, and a generic connection to the car's computer (shown as "electronic box"). The VDO has a digital odometer (which I could use because the Prius odo is also invisible during daylight hours) that also doubles as the calibration setup readout.

The ISSPRO speedometers from ken1784 are good, and don't have the (possibly) extraneous odometer. However, they don't have km/h markings (for Canada, in my case) or an installation manual for the R8450 series. I wrote ISSPRO to ask if the R8460M instructions were appropriate. The ISSPRO speedos have DIP switches on the back to calibrate the speed.

So it appears that electronic speedometers are, indeed, available. The remaining problems are to find a wire on the Prius computer that outputs between 500 and 400k pulses per mile (for the VDO) and possibly designing a small buffer to isolate the Prius computer from the much-less-expensive speedometer in case the speedo itself goes into destructo mode. For that matter, a single IC could be used to translate any number of pulses per mile to the input required by the speedometer.

There must be vehicle speed sensor pulses available somewhere. Or a shaft that rotates proportional to vehicle speed to which a magnet could be affixed. Heck, it probably already has a pickup somwhere (besides the ones on each wheel).

Any delay between the VSS signal and the speedo shouldn't be a problem for the VDO as the speedo integrates the pulses and is pretty well damped.

 

Looks like VDO wins

The ISSPRO 8460 from Ken@Japan looks good and IS129 is the correct installation manual. Curt at ISSPRO tells me the correct manual for the 8450 series is IS073.pdf.

The ISSPROs use input from a magnetic sensor or AC generator. You have to pick a single wheel or a rotating shaft somewhere to mount a sender. I think I'll go with the VDO because it also allows direct connection to the computer and has simpler calibration. VDO model 437 201 looks good.

I s'pose a local hot rod shop (do they still have those?) will have housings for the 3-1/8 to 3-3/8 inch electronic speedometers.

I know this is going to be expensive and a real pain, especially as I am doing at least two Prii. Three if my sister wants one, four if my neighbor does, too. It should get easier by the second or third installation. The parts cost should just about equal that first speeding ticket.

Thanks to all who got involved. I'm really gonna do it!