Digital dash

[Joe Vitek]

Matt,

I know this was answered a number of times and the thread has gotten
kind of long, but I am in the process of doing exactly what you seem to
want to do. I am using a chipset that is quite dated now. They were
originally RCA parts but then Harris bought the RCA, GE, and Intersil
lines. Now Intersil has bought Harris and they are the ones that have it
now. They are the CA3162E A/D and the CA3161E 3digit 7 segment
decoder/driver. The datasheets are available on the Intersil website
(http://www.intersil.com) or I can email them directly to you. The
chipset is designed for exactly what you want to do. With two IC's, you
have a complete gauge with a minimum of parts. There was a good two part
article in the July and September 1990 issues of Radio Electronics
(which I still have) that shows how to build an oil pressure, temp,
volts, fuel, vacuum, and miscellaneous temp gauges for automotive
applications. This could be expanded to other gauges as well. These IC's
are still available from a number of hobby distributors like Digikey
(http://www.digikey.com). As for the tach and speedo, you could use a
PIC with a timer to count pulses from the tach (or Hall effect speed
sensor on the driveshaft for the speedo) and do the math to read out in
mph or rpm. I did a discrete digital logic design for a speedo (or tach)
about 15 years ago that worked very well. Using counters, latches,
timers, and display drivers (and associated gates) I had a working three
digit speedo (4digit tach). Archaic by today's standards. Actually, all
of this could be done with a microcontroller that has A/D capability
(e.g. Mot 68hc11 or TI MSP430C). Then multiplex the displays with
display drivers that will drive the seven segment displays directly
(74ls47). This is my next step for the digital dash project. I know it
probably would be faster (and possibly cheaper) to just buy it
commercially but then it wouldn't be custom for my application, not to
mention the satisfaction when someone looks at it and you tell them it
was built from scratch. I have a lot of info so email me privately if
you are interested in what I have. I am on the digest.

-- 
Joe Vitek  mailto: jvitek at cfl.rr.com
'81 Cutlass Supreme 403/350 (efi 455 soon)
'87 Cutlass Supreme 307/200-4R (efi 403 w/custom digital dash soon)
'89 S10 4banger parts scrounger
'90 Accord (wife has to drive something)

Matt wrote:
> I've been thinking about building a digital dash for my Dart.  While I
> could put together a circuit on my own that does LED bargraph readouts
> without too much trouble, a three digit digital readout would be more
> accurate.  Yesterday I decided to see if I could find any sites on the
> Internet that might list what kind of IC's might be helpful in such a
> circuit.  I got as far as figuring out that I could use some kind of off
> the shelf 8-bit ADC, but is there some kind of chip that will take the
> output from an ADC and use it to control a (preferably three digit) LED
> display?  If so, what's it called, and who makes it?
>        This would be enough for me to put together a digital temperature >gauge,
> fuel gauge, or similar gauge, but I'm also wondering about tachometers and
> speedometers, as a digital tach would be a nice addition.  Is there some
> kind of IC that will accept the kind of signal I can get from the
> distributor as an input, and return a value that corresponds to its
> frequency, or something else I could use for this?
>            Thanks in advance.  There seems to be so many kinds of IC's out > there, I'm
> not sure where to start!
>
> Matt Cramer
> '66 Dart, no EFI (yet)
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