Telementery Ideas

[Frederic Breitwieser]

>	I am about ready to start making telemetry for my race car, what 
>I plan on using is an analog to digital converter connected to the
parallel port, 
>and just write a small program in Basic to store the variables in a text 

True telementry systems transmitt the data into the air.  If you are doing
this, go to www.linxtechnologies.com, as they have serial RF-based
transmitter/reciever pairs.  The new 900MHZ 1/2 mile transmitters (indoors,
more outdoors) can transmit data at 56kb or thereabouts, which is very
suitable for your application.  Plus, it has true serial with handshaking,
unlike their less expensive modules.  A matched pair is about $100 - $120
or so, and requires 6-9 volts and your choice of antenna, a whip, a coil,
or their official small glue on plastic thing.

>to use the ADC0831 with a 4051 Multiplexer so I can have 8 inputs.  Plus 
>other regular TTL lines about 5 in and 7 

Good choice.

>would like to know if a simple frequency to voltage converter would be 
>acurate enough to measure RPM.  Also, the race car hs two 45DCOE6 

There is an older chip, the LM9400 Freq-V and V-Freq.  While its a 10 year
old chip (at least), they were dirt cheap, and fairly stable in their
conversions if you utilizize tantilum capacitors with a high tolerance.
Cheap ceramics or electrolytics in the R/C circuit would allow it to drift
at higher frequencies/voltages.  The beauty of this chip is it can convert
F to V and vice versa on the same chip - just not at the same time.
Anyway, I can dig out a schematic if you tell me you can find them.  I'm
sure by now there are probably 10 good substitutes by now.

>Webers and I was wondering if I could use a O2 sensor, 

There is absolutely nothing stopping you.  Typical OEM O2 sensors vary
between 0 and 1 V, depending on the mixture.  We've discussed the Lambda
(O2) sensor's output before, though off hand I don't recall what 14:1
(Stioch) is, however its probably in the DIYEFI archives somewhere, if no
one jumps aboard this thread and fills you in.

You can use your ADC80xx to read the 0-1V, or if it floats your boat, you
can amplify the signal to 0-5V, giving you the full 8-bits to play with
computer wise. Of course, the more "stuff" between your sensors and your
A/D circuit you'll find you can introduce inaccuracies.  Linear Op-Amps are
very linear, but not perfect.

>or maybe a wide range sensor when that project finishes to measure A/F ratio 
>and then make the changes in the weber, I know the fuel curve has a flat
spot in it.  

Changing your A/F ratio is a matter of adjusting the fuel flow into each
weber tower via a small but strong servo motor.  At this point, you are
approaching the complexity of fuel injection.  BTW, they do make weber
towers with throttle plates that have injector bosses forged/welded at the
base... and it looks very impressive if you are a big tuned Weber fan.

>Also could someone please explain the advantages of a Wide Range 02 meter 
>as opposed to a lambda 02 sensor, thanks.   I will keep the group posted 

The wide range sensor, my understanding is its output is greater than 0-1V,
and can read a very lean mixture with some accuracy.  Most OEM sensors
generate 0-1V and are not entirely linear, but damn close.


Frederic Breitwieser
Bridgeport, CT 06606

Homebrew Automotive Website:
http://www.xephic.dynip.com/

1993 Supercharged Lincoln Continental
1989 HMMWV
2000 Buick-Powered Mid-Engined Sports Car