Re: [DML] Re: Fixed Sat Nav - help please (Delorean related)

[Joe Angell <jangell@xxxxxxxxxxxxxxxxx>]

Incidentally, the DeLorean Motor Center unit (which I think is in the  
$150 range) replaces the speedo cable between the speedometer and the  
LAMBDA unit.  They did the work for me when I had cruise control  
installed just before I moved away from California.  The unit puts  
out 8 pulses per revolution, I think (the pulses per revolution are  
written on it, but I'd have to crawl under the dash to take a look).   
I hooked it up to an oscilloscope at a friend's place where we found  
out that it puts out a sine wave in positive voltage range (I can't  
remember quite what the voltage was; most notably, it didn't swing  
from positive to negative, which I understand magnetic units can  
do).  I plan on tapping into it for some other projects I have  
planned (which can, in part, be boiled down to an elaborate digital  
speedometer).

The unit DMC has consists of the pulse generator (probably an optical  
encoder?) with spinning speedo cables attached to it, making it easy  
to replace the existing cable.  They'll sell you just the pulse  
generator part if you want to construct/obtain your own cables, too,  
although I'm not sure how involved that is.  There are two wires  
coming off of the unit that you connect to whatever needs the pulses.


As for GPS, I'm currently using the TomTom software on my Palm  
Tungsten T3, with TomTom's Bluetooth GPS module sitting on my dash,  
which gives it an adequate view of the sky.  I live in northern  
Vermont, so there aren't exactly a lot of tall buildings here to  
block my LOS, but I've never had any real problems getting an  
accurate signal, even when I drive around Boston, MA or Providence,  
RI.  The worst I've had is when the maps don't match the actual roads  
(because of relatively recent construction, for example), so the  
software thinks I'm driving through a field or missed a turn, but  
that's not too common.

This GPS combo is not tied into the car in any way (except for the  
extra cig lighter sockets I added under the right drivers knee pad to  
power the two devices), but the TomTom software seems to be smart  
enough to account for the once-a-second or so update that the GPS  
unit provides.  As such, it always displays nice, smooth motion by  
extrapolating from previous positions.  If you miss a turn you can  
see it hesitate for a bit, as it briefly believes that you DID make  
the turn, but once you've gone far enough the wrong way (maybe fifty  
to a hundred feet) it jumps to the proper location and accurately  
tracks again.  This could also be explained by the relative  
resolution of GPS, or the quality of the satellite signal at that  
point in time.

The unit also reports the speed, which seems to be fairly accurate.   
Due to the once-a-second or so updates, there is a slight reporting  
lag, but it's not significant; I'm not going to replace my  
speedometer with the GPS signal or anything like that, though.

-- Joe

> When I had my Alpine GPS installed in 17167 at a local circuit city,
> the guys realized in the middle of the installation that the D didn't
> have an electronic speed sensor.  They told me they didn;t have the
> part at the time but if I brought the car back in a week, they would
> have it.  They didn't charge me extra for a crazy alpine speed sensor
> that actually reads pulses from a spinning tire. (however,
> installation was about 120$ if I remember correctly)  They mounted the
> device in the luggage compartment and used a large magnet to magnetize
> 1/2 of the right front tire.  now the speed sensor sends a pulse any
> time it senses the right front tire make a rotation.







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