[Coco] Re: Coco Digest, Vol 10, Issue 24

[farna at att.net]

You're right -- I forgot the joysticks are basically potentiometers for voltage, not resistance. Which puts me back to how the heck I intended to read resistance with them. I had a simple circuit and short routine for that, think I got it from a Rainbow program, but probably not the one I was thinking about. I don't recall now, was around 10 years ago that I stopped. Since the MC-10 only has a serial port for useable I/O, and the CoCo board is just to big, there's no point in pursuing this idea. Unless it was mounted in the trunk... but then you have 8-10 feet of cable going to and from I/O, which would just add resistance and cause other problems... yes, I seem to recall considering and rejecting that idea! There would be 3-4 feet of wiring from under the dash to under the hood anyway!  Oh well, these are some of the reasons I dropped the project, plus cost. Looks like the only snae way to go about it would be to use a separate PIC controller and LED display for each gauge. That's probably why a Dakota Digital gauge setup costs $500 for a six gauge system. I doubt I could build one for half that, plus I'd have to learn the programming. 

The idea of programming a VIC-20 for all this is plain scary! I don't know of anyone who really LIKED Commodore BASIC, though many tolerated it (or just didn't know any better). I've seen the LED graph type gauges, but would rather have a numeric readout as it would be more accurate. LEDs in 5 mph steps would be good enough though. 

Reading all this stuff from you guys does give me the idea again, plus I've been looking at comercially available digital gauges and going into shock. Digital gauge technology is ancient now, there's no reason for it to be so damned expensive! One processor should be able to handle it all with a graphic display. An old 386 or 486 notebook has the power, but can't relocate the screen so easy. Maybe I could find one of the early 386 tablet type computers used. That might work for another car, but the shape of the dash in my 63 Classic would have to be altered to much, and I like the vintage look. Altering the dash that much would destroy the "feel" of the car. 

The hurdles are what's causing the lack of interest more than anything else! The task just gets more daunting the more I think about it in a rational way. If the circuits you have drive LED characters I might be interested, but not interested LED bar graphs. Two digit display should be adequate, though I think I'd go with three for the speedo anyway. 

--
Frank Swygert 
Publisher, "American Independent 
Magazine" (AIM) 
*Elite* publication for those 
interested in all 
aspects of AMC 
history,performance,restoration,etc 
. 
(AMC,Rambler,Nash,Hudson,Jeep,etc.) 
http:farna.home.att.net/AIM.html 
(free download available!) 



-------------- Original message from coco-request at maltedmedia.com: -------------- 

> Message: 3 
> Date: Sat, 7 Aug 2004 22:36:32 EDT 
> From: KnudsenMJ at aol.com 
> Subject: Re: [Coco] MC-10 Questions... 
> To: coco at maltedmedia.com 
> Message-ID: <88.110f96e5.2e46ebb0 at aol.com> 
> Content-Type: text/plain; charset="US-ASCII" 
> 
> In a message dated 8/7/04 9:09:35 PM Eastern Daylight Time, farna at att.net 
> writes: 
> 
> > The other gauges, fuel level, engine temp, oil pressure, and possibly volts 
> ( 
> > haven't figured out how to do that one yet, the other three are simple 
> > variable resistances that I know the ranges for) could be slower. The oil 
> > pressure will have a back-up warning light. The numbers displayed will have 
> > to be on a graphics screen to be big enough to easily see. I'd probably use 
> a 
> > mechanical hour meter under the hood and forget mileage, unless I can find 
> a 
> > stand alone odometer instead of an hour meter. 
> > 
> > Heck, I've forgot how I measured resistance now!! I remember using the 
> > joystick D/A inputs, but that's all. Got the idea from a game that used a 
> > series of push buttons for a Jeapordy style buttons connected to one port. 
> I 
> > think each button had a different resistance and the CoCo could tell which 
> > button was pressed. Might have to have the gauges work in 5 or 10 unit 
> > increments, but would be close enough. 
> 
> I think you're forgetting something -- that the Coco's joystick inputs 
> measure Volts, period. Resistor hookups are just voltage dividers of a known 
> external reference voltage, into a dependent voltage that feeds to the A/D 
> joystick 
> inputs. 
> 
> To monitor your car's battery voltage, which ranges between 12 and 15 or so, 
> use a pair of fixed resistors to divide it by 3, so that range becomes 4 to 5 
> V (remember, the Coco joysticks measure from 0 to 5 V, no more). 
> 
> I think a competitor, maybe Apple, used a similar scheme to the Coco's, but 
> had one of the resistors built into it, so the joystick was just a variable 
> resistance. Not nearly as flexible as our Coco (but then, what was/is?) 
> --Mike K. 

Message: 9
Date: Sat, 7 Aug 2004 21:08:00 -0700 (PDT)
From: Robert Emery <theother_bob at yahoo.com>
Subject: Re: [Coco] MC-10 Questions...
To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
Message-ID: <20040808040800.65286.qmail at web81508.mail.yahoo.com>
Content-Type: text/plain; charset=us-ascii


--- farna at att.net wrote:

> You know, as I was thinking about that digital dash again,
Sounds like someone's been bitten by the bug again... :-)

<snip>
> avg. mpg and estimated distance on remaining fuel).  I doubt the MC-10 could
> do the analog gauges, I'd be happy with a big digit speed and smaller digit
> gauges placed around the central speed readout. That would have to be a
> graphics screen too. 

Since either way it's graphics... the analog gauge would probably be a lot less
work than drawing numeric characters. Does the MC-10 support semigraphics
modes? What about the high speed poke?

Back when you first posted about your desire to do this but thought the CoCo
was too big, I was going to say a VIC-20 would be a good choice (but you said
you'd lost the desire)... I have one (VIC-20) that I'd considered using for
everything but the speedo/tach. Those were handled by dedicated circuits found
in Radio-Electronics from the early or mid 80's. Still have 'em if you're
interested and I know of a ~$35 kit (locally available) which is almost the
exact same circuit, designed to drive LED's.