Digital dash

[Matt Cramer]

At 09:03 PM 4/27/2000 -0400, you wrote:
>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. 

	Thanks, that sounds like exactly the thing I was looking for.  I went to
their website and downloaded the tech sheets for both of the IC's.

>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. 

	That article might be useful, but it doesn't look too hard to design
something that'll let it work with my stock sending units.

>These IC's
>are still available from a number of hobby distributors like Digikey
>(http://www.digikey.com). 

	Thanks for that link, too.  Looks like these gauges could be put together
for a pretty reasonable price.

>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

	Thanks for the suggestions on extending that basic design.  I'll keep them
in mind for future reference.  Right now, I'll probably only do digital
versions of the existing analog gauges except for leaving the speedometer
and adding an oil pressure gauge, as those can be done without cutting up
the dash but it might take some major fabrication to install a digital
speedometer and tach.

Matt Cramer
----------------------------------------------------------------------------
To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes)
in the body of a message (not the subject) to majordomo at lists.diy-efi.org