From: firstname.lastname@example.org (Richard Cochran)
Subject: Re: Electronic Auto Dashboard
Date: 2 Dec 2002 11:33:19 -0800
NNTP-Posting-Date: 2 Dec 2002 19:33:19 GMT
"Ed Price" wrote in message news:...
> Marc & Gary:
> Well, discrete aftermarket gauges are my back-up plan. The existing gauges
> got pretty trashed from sun & water damage under the previous owner, so
> rebuilding them is not very attractive. An analog speedo still looks good,
> but I am concerned about how close I can match a commercial mechanical
> speedo gauge to the mechanical drive off the trans (as I have no idea about
> the ratio of the drive gears). An electronic speedo can compensate for all
> those variables.
> Once you have a digital axle-turns counter signal, you can then work toward
> an electronic odometer. I am looking for some inspiration in the area of
> counting, scaling and storing that data. Maybe a microprocessor is the best
> way to do it. But I have to find a comfortable balance of build / buy for
> the electronics (just as with the mechanicals, where I certainly don't
> intend to machine my own ball bearings). I don't think I want to start the
> project at the level of coding a Basic Stamp system.
A wild and crazy thought: have you considered a bicycle speedometer?
Inexpensive, rugged, pre-made, debugged. They typically work on a
sensor that "sees" a magnet pass by once for every turn of the bicycle
wheel, and you calibrate them by telling them how far the vehicle moves
for each pass of the magnet. You might be able to mount the sensor
on the driveshaft, axle, or similar, as long as the distance between
pulses fit within the speedometer's range.
Bonus: they almost all can display average speed for a trip,
max speed, trip odometer (to .01 mile, typically), plus a "total distance"
odometer independent of the trip odometer.
Downsides: it's probably small, maybe ugly, and doesn't display the other
info (engine temperatures/pressures and the like) that you're interested
in. The odometer probably resets on battery change.