Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!mips!pacbell.com!ucsd!nosc!crash!simpact!cmkrnl!jeh
From: jeh@cmkrnl.uucp
Newsgroups: sci.electronics
Subject: Re: Digital dash (was: Inductive pickups.
Message-ID: <1991Jun3.152425.70@cmkrnl.uucp>
Date: 3 Jun 91 22:24:25 GMT
References: <1970@ole.UUCP> <1991May30.151040.50@cmkrnl.uucp> <1973@ole.UUCP>
Organization: Kernel Mode Consulting, San Diego CA
Lines: 74

In article <1973@ole.UUCP>, ssave@ole.UUCP (Shailendra Save) writes:
> In article <1991May30.151040.50@cmkrnl.uucp>, Jamie Hanrahan writes:
>> Projects for such have been appearing in the hobby mags every now and then for
>> almost forever.  There was even one in one of the trade magazines, _EDN_ I
>> believe, circa 1974 (!) or 75 or so. That one was for a motorcycle. 
> 
>   I am aware of this. The idea behind this venture is to make more
>   than a just the run of the mill "digital dash"  Most articles
>   (projects) in the mags do not come close. Even if they did, I would
>   not use them. Takes the fun out of experimenting.

Then, taking your position to an extreme, you shouldn't be asking the net for
hints on driveshaft speed pickups -- experiment and figure it out for yourself!

Seriously, stumbling down blind alleys where others have gone before takes some
of the fun out of experimenting too.  It's useful to look at others' work if
only to get an idea of what not to do -- not necessarily for making a direct
copy. 

That _EDN_ project, for instance, used only SSI and MSI TTL!!!  And it provided
only "dumb displays".  No way would anyone copy that today.  Still, there might
be some good ideas on signal pickup techniques, if nothing else.  

>> .  For instance, my water temp.
>> gauge swings almost up to the red part of the scale as the car warms up, and
>> then the thermostat opens and it goes down to the middle of its range where
>> it's supposed to be.  What would be nifty would be something that would draw my
>> attention to that gauge if the reading stayed up near the redline for more than
>> a few minutes.  
> 
>   I think you need to have your thermostat looked at. The temp should
>   approach red. Never be *in* it. Especially with summer coming up.

I think you need to read the articles you respond to a bit more carefully.  I
said it gets "almost up to the red part", not *in* it.  The car is running 
fine, thank you, and can take either side of the Grapevine at prevailing 
traffic speeds in the summer with the air conditioner *on*, with not even a
hint of overheating.  

But my underlying point is that a simple good-warning-bad indicator, based 
solely on statically-defined ranges, is not really adequate.  And as long as
you're using a micro, you *can* do a better job.  In my example, I'd want to be 
warned if my temp gauge was up *near* the red area for more than fifteen 
seconds or so, even if it isn't *in* the red area, because that would be a 
change from the car's typical behavior.  Similarly I'd want to be warned if
the gauge did *not* get near the red area during warm-up -- either the 
thermostat is staying open all the time, or the temperature sensor has gone
bad.  

>   One final note. Digital becomes better when there is something
>   intellegent you can do with the reading. 

No argument here!  But that doesn't mean that the readouts have to be digital,
only the processing.  

> I intend to use a 6811
>   microcontroller which will tell me things like trip distance, miles
>   per gallon, total distance, shift up (rpm too high), shift down
>   (angle of car upwards or downwards, rpm too low)  and other things
>   like that. Why all this? Because it is fun. Because it comes free.
>   I have lots of free ports on the I/O. Because it is a challenge.
>   Cars are some of the noisiest environments you can work with.
>   Because I like to do things myself. And finally, because I don't 
>   have a tach or battery guage on my dash ^_^

Hey, no one said "don't do it"!  All I said was "*I* wouldn't use digital 
readouts on the dash".  Go for it.  Experiment.  Try lots of options.  
Interface to a G-Meter while you're at it!!!  Then write it up and sell it
to one of the hobby mags, both to recoup some of your parts costs, and so 
that the rest of us can learn from YOUR experience!  

	--- Jamie Hanrahan, Kernel Mode Consulting, San Diego CA
Internet:  jeh@dcs.simpact.com, hanrahan@eisner.decus.org, or jeh@crash.cts.com
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