[Diy_efi] Data Logger CPU schematic and C for review

[Bernd Felsche]

On Monday 05 February 2007 07:44, Robert W Hughes wrote:
> >> What would also be interesting would be the ability to directly

> > I've toyed with the idea of using RC-servos to do the needle
> > positioning on stock gauges. The servos are controlled by pulse
> > width and (I understand) will lock when they get no further signal.
> > Even removing power leaves the servo locked in position.

> > This by-passes the need to fake various types of signal and allows
> > for other interesting analogue gauge functions to be programmed.
> > Also, pulses only need to be sent to the gauge when the indicated
> > value is to change.

> Most late model cars use air core meters which can do 90 or 270
> degree or more sweeps. Check out the Phillips driver SA5778D at
> http://www.ortodoxism.ro/datasheets/philips/SA5778D.pdf  for an
> idea of what is involved. This chip accepts a serial bit string to
> drive two 90deg meters and one 270 with .35deg resolution and
> could probably drive the instruments in a car panel with whatever
> you wanted to digitize and send out. I think most manufacturers
> are using something like this in their panels now to cut down on
> wiring and connector pin count.

Thanks for the pointer. First time I tried to download using that
URL I got "403 Forbidden" ... I googled and found the datasheet
by other means. It's an interesting device.

The reason for the RC-servo was to replace the guts of gauges in
"classic" cars and to maintain the traditional face. Sweep rates of
about 0.1 to 0.2 seconds are entire acceptable and a variety of
sweep angles are available at much lower cost than "original"
replacement gauges.

Air-core meters are by themselves less robust than RC-servos but
should be OK if already on the gauges in place in the "dashboard".
My need for robustness comes from having a surplus of left thumbs
that increases with the square of the delicacy of the components I'm
handling.

-- 
/"\ Bernd Felsche - Innovative Reckoning, Perth, Western Australia
\ /  ASCII ribbon campaign | "If we let things terrify us,
 X   against HTML mail     |  life will not be worth living."
/ \  and postings          | Lucius Annaeus Seneca, c. 4BC - 65AD.