6 Apr
1999
6 Apr
'99
8:58 a.m.
Jason Willgruber wrote:
I'm not sure if anyone else knows about what I'm talking about, but in my
Jeep (pre-ABS), there's a little panel on the dashboard (not original).
There's 4 LED's on the panel (one corresponding to each wheel). When the
wheel corresponding to a particular LED is completely stopped, the LED
lights steadily red. When the wheel is turning, the LED flashes green (one
flash for each revolution).
Anyone know how this would work (with out me pulling it out of my Jeep)? It
would be probably a good accessory for non-ABS cars.
--
-Jason Willgruber
(roblwill(a)usaor.net)
ICQ#: 1730318
<http://members.tripod.com/general_1>
It's probably a similar system to the one used by Etak with their early
car navigation systems. Basically, they used a special adhesive tape
that contained a small bar magnet every inch along its length. This was
applied to the circumference of the inside of each front wheel rim, and
a Hall effect sensor was attached to a point on the front axle (usually
to a part of the brake caliper assembly) where it was within an inch of
this tape as it passed by. Each magnet passage would produce a countable
pulse, and the Etak computer could determine the wheel speed and
direction of rotation for each front wheel. *Supposedly* it could also
detect a turn by the differential speed of the front wheels, but it also
had a flux gate compass to help determine direction and turns.
A pretty clever system that worked quite well, considering it was all
done without reference to external navigation data sources like GPS,
LORAN, etc!
Since your system apparently produces only a single pulse per
revolution, I would guess there's one magnet somewhere on each wheel
rim. The speed resolution with only a single pulse per revolution is
probably not good enough for ABS use.
Hope this helps,
Stan